Studies on the factors involved in the use of sodium arsenate dusts against the Mormon cricket
(Anabrus simplex Hald)
by Ellsworth B Hastings
A THESIS Submitted to the Graduate Committee in partial fulfillment of the requirements for the
degree of Master of Science in Entomology
Montana State University
© Copyright by Ellsworth B Hastings (1939)
Abstract:
Evidence is brought out to show that the commercial sodium arsenite used in cricket control probably
consists of a mixture of meta sodium, several derivatives of pyro sodium arsenite, and free arsenlous
oxide. The several diluents under trial were found to be inert when used in connection with cricket
dusts and the uniformity of the dust cloud was found to depend largely on the state of subdivision of
the particles. A uniform product of sodium arsenite and diluent could be obtained after very short
period of mixing. In addition, the jarring of containers did not appreciably alter the concentration of
sodium arsenite and diluent either on the top or bottom of the containers.
In treating Mormon crickets, sodium arsenite was found to be effective when applied either as a contact
or stomach poison and to be less effective when applied to the tarsi only. It was also found that an
increase in temperature would enhance, the killing properties of the dusts both in the case of mature
and immature crickets. The removal of dusts from the cricket body even after 90 minutes has lapsed,
affects the mortality obtained. Evidence was also presented to show that crickets become inactive after
a short time on the surface of a body of water and if allowed to remain there death may occur. STUDIES ON THE FACTORS INVOLVED IN THE USE OF SODIUM ARSENITE
DUSTS AGAINST THE MORMON CRICKET (ANAERUS SIMPT.-g?
ty
ELLSWORTH B. HASTINGS
A THESIS
Submitted to th e Graduate Committee
in
p a r t i a l fu lfillm e n t o f th e requirem ents
f o r th e degree of
Master o f Science in Entomology
at
Montana S ta te College
Approved;
In ChargtfTof IlaAiA Work
Chairman, Examihing Committee
‘'Chairman. Graduate Committee
Bozeman, Montana
June, 1939
,)
/3 7 /
7fs
-2 -
TABLE OF CONTENTS
Page
A b stract ..................................... . . . . . .
3
In tro d u ctio n .........................................
. .
4
................. .........................
5
Acknowledgments
Review of previous Work
.............................
6
Section I
Chemistry of Sodium A rsen ite ................. ..................... ,
S
Time of M ix in g ..................................... ................................
12
Carrying P ro p e rtie s of D iluents
. . .........................
15
J a rrin g E ffe c ts on Mixed Dusts ............................. . .
25
S ection I I
P erm eab ility and i t s C o n trolling F actors .................
29
V a ria tio n s in B io lo g ic al M aterial . .............................
31
The Action o f Dusts when Applied to Various Regions
o f the In se c t B o d y .........................................
32
—y
Temperature E ffe c ts on Action o f Dusts . . . . . .
38
TC
f*
The In e rt Nature of the D i l u e n t s .........................
42
Length of Time Dusts must Remain on In se c t Body . .
U3
Water B a r r i e r s ................................................................. .
45
Summary
47
'Si
.................................................
L ite ra tu re C ited .................................................................
62352
50
->
•ABSTRACT
Evidence i s brought out to show th a t the commercial sodium a rs e n ite
used in c ric k e t c o n tro l probably c o n sists of a m ixture of meta sodium,
se v era l d e riv a tiv e s o f pyro sodium a rs e n ite , and fre e arsenious oxide.
The
se v era l d ilu e n ts under t r i a l were found to be i n e r t when used in connection
w ith c ric k e t d u sts and th e unifo rm ity o f th e dust cloud was found to depend
la rg e ly on the s t a te of subdivision of the p a r t i c l e s .
A uniform product of
sodium a rs e n ite and d ilu e n t could be obtained a f t e r very sh o rt p e rio d of
mixing.
In a d d itio n , the ja r r in g o f co n tain ers did not appreciably a l t e r the
co n cen tratio n of sodium a rs e n ite and d ilu e n t e ith e r on th e top or bottom of
the c o n ta in e rs.
In tr e a tin g Mormon c ric k e ts , sodium a rs e n ite was found to be
e ffe c tiv e when a p p lied e ith e r as a contact o r stomach poison and to be le s s
e ffe c tiv e when ap p lied to th e t a r s i only.
I t was also found th a t an in cre ase
in tem perature would enhance, the k i l l i n g p ro p e rtie s o f th e d u sts both in
the case o f mature and immature c ric k e ts .
The removal o f d usts from th e
c ric k e t body even a f t e r $0 m inutes has lap sed , a ff e c ts the m o rta lity
obtained.
Evidence was also p rese n te d to show th a t c ric k e ts become in a c tiv e
a f t e r a sh o rt time on th e su rface o f a body of water and i f allow ed to
remain th e re death may occur.
-U INTEODUCTIOH
During th e p a st two y ears the co n tro l of Mormon c ric k e ts (Anahrus
simplex Said..) in Montana as w ell as in a number of neighboring S ta te s , has
been one o f the major entom ological problem s.
Although Mormon c ric k e t
outbreaks have been recorded in e a r l ie r tim es, th e f i r s t a c tiv e co n tro l
campaign in which a rs e n ic a ls were used to any extent was in 1927.
In
general the a rs e n ic a l dusts used during the p a s t two y ears were the same as
those employed in th e 1927 campaign.
The p rin c ip a l d iffe re n c e has been the
change from hydrated lime to diatomaceous e a rth as the d ilu e n t, the l a t t e r
m a te ria l causing le s s discom fort and i r r i t a t i o n to the dust gun o p e ra to rs.
Nine hundred tons o f mixed sodium a rs e n ite dusts were used in
s ix w estern S ta te s during the 1937, and approxim ately tw ice th a t amount
during the 1933 Mormon c ric k e t campaigns.
Nearly h a lf of the e n tire amounts
re fe rre d to above were used in Montana.
An emergency campaign of th is type n e c e ssa rily lead s to many,
problems concerning the in s e c tic id e s used, t h e i r p ro p e rtie s , p re p a ra tio n ,
and a p p lic a tio n .
Some of the more im portant problems included a need fo r
a c le a re r understanding of the chemical composition of the a rs e n ic a ls used,
the p h y sical p ro p e rtie s o f the d u sts, and t h e ir p o ssib le e ffe c ts upon the
in s e c t.
The follow ing paper i s divided in to two se c tio n s.
The f i r s t
se c tio n includes a discussion of the chem istry of sodium a rs e n ite and the
p h y sic al p ro p e rtie s o f a number of d u sts.
The second se c tio n deals with
the mode o f a c tio n of the dusts on th e Mormon c ric k e t (A. simplex H ald.)
and th e fa c to rs which may in flu e n ce th e ir to x ic ity .
-5 -
ACDTOmnDGmtTS
The w rite r wishes to acknowledge h is indebtedness to Dr, A. L.
Strand fo r h is proposal o f the problem, to J , H. Pepper fo r h is continued
in te r e s t and a id in a tta c k in g the problems embodied in th is paper, and to
Dr. E. B. M ills and D. J . P le tsc h fo r th e ir h e lp fu l suggestions and a id
in p rep arin g th e paper.
-6 -
EEVIEW OP PEZVIOUS WOEK
One o f the f i r s t papers to appear on the use of sodium a rs e n ite
in Mormon c ric k e t co n tro l was th a t of Shotwell and Cowan (7 ).
This paper
s ta te s th a t when dusting c ric k e ts w ith s tr a ig h t sodium a rs e n ite powder
e x ce llen t k i l l s were obtained in every in stan c e up to and inclu d in g twenty
fe e t from th e p o in t of a p p lic a tio n .
I t fu rth e r p o in ts out th e in ju rio u s
e ff e c ts to v e g etatio n , wherever p re s e n t, i f s tr a ig h t sodium a rs e n ite i s
ap p lied .
Cowan (2 ), a y ear l a t e r , s ta te d th a t of a l l the m a te ria ls te s te d
powdered a rs e n ite s o f sodium and calcium proved the most e ffe c tiv e .
He
fu rth e r s ta te d th a t e ith e r of th ese m a te ria ls mixed w ith hydrated lime
in th e proper p ro p o rtio n s and dusted over the swarms was very e ffe c tiv e
®5®i-0-st th is in se c t in almost any stage of i t s development, th a t r e s u lts
could he seen in from twelve to tw enty-four hours a f t e r a p p lic a tio n , and
th a t the m o rta lity among c ric k e ts a t the end o f a four-day p e rio d ranged
from 75 to 100 p e r cen t.
Schweis and Burge ( 6) , in connection w ith t h e ir work on Mormon
c ric k e ts in Nevada, s ta te th a t upon contact w ith the in s e c t the lime and
sodium a rs e n ite s e ts up an i r r i t a t i o n , causing the c ric k e t to attem pt
clean in g i t s antennae and fo o tp a rts by passing them through i t s mouth.
In t h i s way the a rse n ic i s taken in to th e stomach, re s u ltin g in a slow
death which u su a lly occurs between 24 and 43 hours, a c e rta in percentage
re q u irin g as high as 170 hours.
They fu rth e r s t a te th a t m oisture in the
atmosphere appears to in c re a se e ffe c tiv e n e ss of the poison, apparently
in c re a sin g i t s i r r i t a t i n g q u a lity .
-7 -
B ales (I) published work on s u b s titu tin g diatomaceous e a rth fo r
hydrated lime as th e d ilu e n t.
He s ta te d th a t an equal volume (2 pounds)
o f diatomaceous e a rth had been s u b s titu te d fo r the lime and encouraging
r e s u lts had been obtained.
B e tte r d isp e rsa l w ith quicker k i l l was p o ssib le
than in the case where lime was used.
He fu rth e r s ta te d th a t in
experim ental cages 100* k i l l had been obtained w ith 2 pounds of white
sodium a rs e n ite and 5 'pounds o f diatomaceous e a rth .
The r a p id ity with
which the poison k i ll e d was g re a tly in creased w ith tem peratures above 90®F.
Glover (J) in h is work w ith the American cockroach (P e rip la n e ta
—e r i cana (L )), showed th a t sodium a rs e n ite p e n e tra te d th e integument of
cockroaches much f a s t e r than arsenious oxide.
His r e s u lts showed d e fin ite ly ,
however, th a t a rs e n ic would p e n e tra te through the integument o f a cock­
roach to some extent in e ith e r form i f enough time was allowed.
When ra th e r
high co n cen trations are b u i lt up in the cockroach body, a rse n ic may be
recovered in a l l p a rts and tis s u e s .
Such co n cen tratio n s were found when
sodium a rs e n ite was ap p lied as the to x ic a n t, while w ith the much le s s
so lu b le arsenious oxide th e d is tr ib u tio n of a rse n ic was p r a c tic a lly lim ite d
to the d ig e stiv e t r a c t and the p a r ts and tis s u e s near the p o in t of
a p p lic a tio n .
-8 -
SECTION I
CHEMISTBY OP SODIUM AESENI TE
Soditua a rs e n lte in the dry s ta te may e x is t as a tru e compound
in any one o f the follow ing m olecular combinations:
Ortho sodium a rs e n lte
(Na^As O j), Pyro sodium a rs e n lte (NaijAsgO^), o r Meta sodium a rs e n lte
(NaAsOg).
These substances a re b eliev ed to io n iz e when in so lu tio n in the
follow ing manner; meta (NaAsO2^N atAssO i ) ; ortho (N a ^ A s O jJ N a t-AsOj"
Pyro (Nai1A sg O j^tea+ A sg O 5" - ^
);
.
Several methods for th e production of sodium a rs e n lte a re known
and employed. The p a r tic u la r compound used in c ric k e t c o n tro l i s produced
V
by the arsen io u s oxide - sodium hydroxide method. The d i f f ic u lt y in knowing
p re c is e ly what form of sodium a rs e n lte i s being produced may be re a d ily
understood by a study o f fig u re I along w ith i t s subsequent d iscu ssio n .
Pigure I embodies the r e s u lts of stu d ie s made by F.A.H. Shrienmaker and W. C. deBaat as d escribed by M ellor (4) on th e system Na2O-As2
O3-H2O a t 30eC.
Here "a" denotes th e s o lu b ility o f As2Oj in H2O; the
region abA, the su p ersa tu ra ted so lu tio n w ith As2O^ as the s o lid phase;
bcB, o f the s o lid phase NaAsO2 (meta sodium a rs e n lte ) ; cdC, o f the s o lid
Nai1As2Q j1SH2O (hydrated pyro sodium a rs e n lte ) ; deD, o f the s o lid
NaioAsliPl l l SCH2O (a hydrated d e riv a tiv e of p yro); efE, o f the s o lid
Nai1As2Oj (pyro sodium a r s e n l t e ) ; and fgF o f the hydrated NaOH1H2O1 The
s o lu b ility curve ab shows the ra p id in cre ase in the s o lu b ility of As2Oj
as the p ro p o rtio n s of a lk a li in c re a se .
Consider the a re a bcB, wherein the s o lid m a te ria l HaAsO2 e x is ts .
“ 9"
A As* O1
NaAsOz
Na 4 A sz O5
9
so
NaOH so
Hz O
fig u re I . EqiU ililriu m Liagrssi fo r the System EapOAs2O^ - H2O a t 30°C. (from E e llo r (Uj ) .
-1 0 '
Any co n cen tratio n s of the components under equilibrium conditions
which f a l l w ith in t h is a re a may he expected to combine to form NaAsOg
(meta sodium a r s e n ite ) .
Any p o in t w ith in t h is a re a re p re se n ts the
co n cen tratio n s o f the th re e components, As^Oy
fo r th e production of NaAsOg.
mentioned a re a .
and E^O1 necessary
lake the p o in ts X and Y w ithin the a fo re ­
At equilibrium the co n cen tratio n of the th re e components
a re as follow s: a t X, AsgO^ Uo$, NagO 20#, EgO 4o#; a t Y, As2Oj &)#.
NagO 20#, HgO 20#.
Only under equilibrium conditions i s i t p o ssib le to
o b tain the pure compound as in d ic a te d in the shaded a re a s .
Otherwise,
m ixtures o f unknown p ro p o rtio n s may be obtained.
A. Stavenhagen, according to M ellor (4 ), produced sodium a rs e n ite
NajAsOj by h e atin g fin e ly powdered AsgOj w ith an excess o f an alc o h o lic
so lu tio n of NaOH, and B. L. V anzetti made sodium ortho a rs e n ite by re a c tin g
on AsgO^ w ith sodium methozide in accordance w ith .the follow ing equation:
As2O3 + 6NaO C2j ■ 2 Na3AsOj + 3(C2j)gO.
N eith er o f the above methods a re
used to any extent in the production o f sodium a rs e n ite fo r in s e c tic id a l
purposes.
The f in e ly powdered oxide (AsgOj) i s not e a s ily w etted by w ater,
b u t a so lu tio n can be prepared by b o ilin g .
I t a lso d isso lv e s in warm sodium
b icarbonate so lu tio n , w ith evolution of COg, and form ation of e ith e r or both
th e meta and ortho sodium a rs e n lte s , Na3AsOj or NaAsO2 re s p e c tiv e ly , depend­
in g on the equilibrium c o n d itio n s.
The sodium bicarbonate method i s used fo r the p re p a ra tio n of
the sodium a rs e n ite employed in the Standard stock dip a g a in st Hocky
Mountain sp o tted fe v e r t ic k (Dermacentor a n d erso n i).
I t i s not known
-1 1 -
whether the product obtained i s ortho or meta or a m ixture of the two
sodium a r s e n ite s .
The exclusive use of t h is product in dipping stock may
p o ssib ly be due to the fa c t th a t i t has proven su ccessfu l in c o n tro llin g
tic k s w ithout in ju ry to th e stock.
Also, w ith th e p o s s ib i l i ty o f serio u s
in ju ry to stock from burning in mind, work w ith sodium a rs e n lte manufactured
by o th er methods has not been undertaken.
In ev alu atin g sodium a rs e n lte fo r in s e c tic id a l purposes, i t i s
customary to consider the AsgO^ co n ten t.
On the b a s is o f equivalents the
sodium a rs e n lte compounds. so f a r mentioned in th is paper contain th e
follow ing percentages o f AsgO^:
ortho sodium a rs e n lte (Na-^lsO3) 73.S4$;
meta sodium a rs e n lte (NaAsOg) 76.15#; pyro sodium a rs e n lte (NatyAsgO^) 6l.4g#;
hydrated pyro sodium a rs e n lte (NaljAsgO5.SH2O) 41.25#; and the so lid
(Nai0As4On . 26H20) 34.38#.
The s p e c ific a tio n s fo r the dry sodium a rs e n lte used in the rec en t
c ric k e t campaigns c a lle d fo r not le s s than SO# As2O3 co ntent.
By referen ce
to the previous discu ssio n of As2O3 contents o f sodium a rs e n lte compounds,
i t w ill be seen th a t none of the e sta b lis h e d formulae o f th e tru e chemical
compounds contain such a high percentage o f As2O3.
The pure meta sodium
a rs e n lte comes n e a re st to meeting the s p e c ific a tio n s , but in view o f the
fa c t th a t the sodium a rs e n lte manufactured fo r c ric k e t dust i s a m ixture of
the sev eral sodium a rs e n ite s , a l l containing le s s than 76.15# As2O3, i t is
reasonable to assume th a t the a d d itio n a l As2O3 content i s added as As2O3
to meet the req u ire d s p e c ific a tio n s .
With referen ce to L. C. G lover's (3) work on the p e n e tra tio n of
c e rta in a rs e n ic a l compounds in to the body of th e American cockroach
-1 2 -
(P e rlp la n e ta amerlcana (L) ) , wherein he showed the hig h ly In so lu b le JLsgO-j
to he much le s s permeable to the in s e c t Integument than sodium a rs e n ite ,
i t would appear th a t the value of arsenious oxide as a dust i s q u estionable.
One may assume then th a t the AsgOy as such, when added to c ric k e t dust
stren g th en s th e in s e c tic id a l powers of the m ateria l only very s lig h tly .
A l e t t e r received from th e Chipman Chemical Company, from whom
the g re a te s t p o rtio n of the sodium a rs e n ite used in th e I 93S c ric k e t campaign
was purchased, describes th e ir product as follow s:
"Mostly Na2Hi4As1^Og w ith
p o ssib ly some NaH2AsjQg. . . . . Our product i s thought to be la rg e ly the
ortho a rs e n ite but containing an excess o f As2Oj over the normal ortho
pro du ct".
No doubt th ese formulae were derived from an a n a ly sis o f the p ro d u ct.
However, in d eriv in g them from a m ixture o f sodium a rs e n ite and As2O jl i t
appears more probable th a t th e b a sic m ateria l i s the meta ra th e r than the
ortho sodium a rs e n ite .
S ta rtin g w ith the meta a rs e n ite NaAsO2 and adding
one molecule o f As2Oj and one molecule o f H2O, the form ula NaH2AsjOg
reso lv es i t s e l f .
Likewise, s ta r tin g with NaAsO2 and adding another molecule
o f th is compound p lu s one molecule o f As2Oj p lu s two m olecules of w ater,
the compound Na2Hl4Asi4Og i s obtained. • No evidence can be found to show th a t
Na2Hl4Asl4O9 i s a tru e compound.
In a l l p r o b a b ility i t i s a m ixture of
meta sodium a r s e n ite , As2O j1 and w ater.
TIME O I MIXINO
A m odification of the standard io d in e t i t r a t i o n method fo r
determ ining a rse n ic was used C S ).
Since i t was not p o ss ib le to a s c e rta in
-1 3 -
th e exact chemical composition of the sodium a rs e n ite employed in the
experim ents, the value o f the standard iodine was c a lc u la te d in terms of
sodium a rs e n ite in ste a d of the AsgOj co n ten t.
This n e c e s s ita te d repeated
sta n d ard iza tio n s throughout the e n tir e s e rie s of experim ents.
To determine the e ffe c t o f th e d ilu e n ts on th e t i t r a t i o n procedure,
a s e r ie s of weighed samples of sodium a rs e n ite were U ltim ately mixed w ith
the c a r r ie r s and t i t r a t e d .
Table I embodies the r e s u lts obtained.
The
amount of sodium a rs e n ite recovered in each t i t r a t i o n proves th e method to
be w ell w ithin experim ental e rro r.
The question has o ften a ris e n as to the len g th of time necessary
to mix sodium a rs e n ite and c a r r ie r to o btain a uniform m ixture.
To o b tain an in d ic a tio n o f the u n iform ity o f th e dust used in
th e f ie ld , eleven samples of I gram each were removed from drums of mixed
dusts and t i t r a t e d .
The dust had been mixed fo r 20 minutes in a power m ixer,
and th e o rig in a l p ro p o rtio n s introduced were approxim ately 3 to I
diatomaceous e a rth and sodium a rs e n ite .
The samples showed the follow ing
p ro p o rtio n s by weight of the diatomaceous e a rth to one p a rt of sodium
a rs e n ite : 3.U2, 3.35. 3.11. 3.13. 2.78, 2. 34, 3 . 24, 3.48, 3. 62, 2. 01, 3. 68.
The average fo r the 11 samples was 3.07.
Table I I shows th e r e s u lts obtained when I gram samples o f dust
were removed from each of two d iffe re n t types o f m ixers, b a ll m ill and f i e l d
m ixers, a t sta te d in te r v a ls and t i t r a t e d .
The b a l l m ill was the common
la b o ra to ry type of one g allo n c ap a city which revolved a t th e r a t e of 66
re v o lu tio n s p e r minute.
The f i e l d mixer was a power driven custom b u i lt
drum which was se t on an e c c e n tric .
The drum revolved 15 tim es p e r minute
and had a cap acity o f approxim ately 400 pounds.
TABLE I . -B e s u lts of the determ ination o f a known q u a n tity of
sodium a rs e n ite in the presence of a 3:1 m ixture of various d u sts, t y the
t i t r a t i o n method.
D iluent
Weighed amount of
Sodium A rsen ite
in mg.
Mg. of sodium
a rs e n ite determined
by t i t r a t i o n
Average
Sodium A rsen ite
100
100
100
100
100
100
100
100
■
Sodium A rsen ite
+ Diatomaceous
E arth
100
100 100
100
Sodium A rsen ite
+ C e lite
—
100
100
100
100
99.95
100.25
99.95
99.35
Sodium A rsen ite
+ Hydrated Lime
100
100
100
100
98.90
99.00
99.00
99.95
Sodium A rsen ite
+ Calcium Carbonate
100
100
100
100
99.65
99.65
100.10
100.25
99.91
Sodium A rsen ite
+ B entonite
-
100
100
100 *■
100
100.53
99.33
99.09
99.33
99.57
Sodium A rsen ite
+ Volcanic Ash
-
100
100
100
100
97.50
101.20
98.40
96.55
.
99.65
100. 1«)
99.65
99.95
99-57
99.70
100.45
100*06
98.61
97.89
99-09
99.33
99.9%
98.73
99.88
99.21
Sj
CO
O’
-1 5 -
TABLS I I .-P ro p o rtio n "by weight of diatomaceoua e a rth to one p a rt
of sodixun a rs e n ite as determined "by one gram samples taken from mixers a t
the time in te r v a ls noted.
Time in
minutes
5
10 .
15
20
25
30
4o
50
6o
P roportions by weight of D. e a rth to I p a rt sodium a rs e n ite
B all M ill
F ie ld Mixer
Sample I
Sample 2
Sample I
Sample 2
: 4.74
4.85
3.48
3.35
3.28
2.78
3J7
3.30
3.54
1.96
3.5%
3.18
3.50
3.72
2.56.
3.04
3.61
3-58
'"
3-52
3.49
3.44
3.45
.~
3.4c
3.28
3.36
3.57
I t w ill "be noted th a t a f a i r l y constant m ixture was obtained in
samples taken from th e b a ll m ill a f t e r a ten-m inute p e rio d .
Samples from
th e f i e l d mixer proved to be somewhat more e r r a t i c , although w ith the
exception o f one sample a l l approached a 3 to I m ixture a f t e r fiv e m inutes.
This in d ic a te s th a t prolonged p erio d s o f mixing a re not necessary to o b tain
a reasonably uniform product.
CARRYING PROPERTIES OF DILUZNTS
One of th e problems to be considered in connection w ith f i e l d
a p p lic a tio n s o f dusts was the width of swath w ithin which an approximate
3 to I co n cen tration of d ilu e n t and sodium a rs e n ite e x is te d .
The wind
v e lo c ity as w ell as th e fo rc e a p p lied a t th e nozzle would, of course, have
a d ire c t in flu en ce on th e problem.
I n e rt m a te ria l added to the sodium
a rs e n ite had been thought to a c t both in the ro le of c a r r ie r fo r th e a c tiv e
-1 6 -
in g red ien t and as a d ilu e n t.
A lso, any p a rt of the dust cloud was
considered to contain an approximate 3 to I m ixture.
The e rro rs in these
conceptions w ill he po in ted out in the follow ing work.
A s e rie s o f experiments was planned w ith the o b ject in mind o f
o b tain in g a c le a re r p ic tu re of the r o le o f the in e r t in g re d ie n t, as w ell as
some d e fin ite knowledge as to the concentration of sodium a rs e n ite through­
out the dust cloud.
The work was done in a room approxim ately 25 fe e t long
and 10 fe e t wide which was tig h t l y closed to elim in ate any p o ss ib le e ffe c ts
from a i r c u rre n ts o th er than those caused by the small dust nozzle.
IProm
observations made on the dust cloud, o th er a i r c u rre n ts p re se n t appeared
in s ig n if ic a n t.
Mixed d u sts were blown out from a nozzle h e ld two f e e t above and
one foot back Of the f i r s t o f a s e rie s o f p e tr i e d ish e s, placed one foot
a p art fo r a d istan c e of 14 f e e t.
The dust nozzle which was used ap p lied the p rin c ip le o f the
Venturi tube.
I t was c o n stru cted o f a 12-inch p iec e o f 6 mm. g la ss tubing
c o n s tric te d in th e c en ter a t which p lac e a p iec e of 3 mm. g la s s tubing was
sealed^
A constant a i r p ressu re was ap p lied to th e la rg e r tube, thus
c re a tin g a vacuum in the sm aller one.
During dusting op eratio n s th e end
o f the small tube was kept immersed in a v e sse l o f the d u st.
A q u ite uniform
f in e ly divided dust cloud was obtained.
A fte r a heavy cloud had been blown out over the p e tr i e d ish es,
the dust was allow ed to s e t t l e u n t i l the a i r was c le a r .
The samples
obtained in th is manner were then weighed and t i t r a t e d to determine the
p ro p o rtio n s o f sodium a rs e n ite and i n e r t m a te ria l.
The o rig in a l concentration by weight of the m a te ria l a s i t l e f t
-1 7 -
the dust nozzle was in the p ro p o rtio n of th re e p a r ts i n e r t in g re d ie n t to
one p a rt commercial sodium a rs e n ite .
Table I I I , rep resen ted g ra p h ic a lly in fig u re s 2 and 3, embodies
th e r e s u lts obtained from the foregoing experim ents.
p h y sical asp ects o f the d ilu e n t used.
Table IV l i s t s some
Photomicrographic p ic tu re s o f each
d ilu e n t w ill be found in fig u re 4 .
Consider the curve fo r diatomaceous e a rth as shown in fig u re 2.
I t w ill be noted th a t a number of samples near th e nozzle contained a higher
p ro p o rtio n of sodium a rs e n ite than o f the in e r t in g re d ie n t, thus In d ic a tin g
th a t a la rg e percentage o f the sodium a rs e n ite had f a lle n out of th e m ixture
near the source.
A l to 3 m ixture o f sodium a rs e n ite and i n e r t in g red ien t
was obtained a t a p o in t approxim ately
fe e t from th e nozzle.
From th is
p o in t out the curve r i s e s a b ru p tly showing a very d ilu te d u st, as a
consequence of previous ra p id s e t tl i n g of sodium a rs e n ite .
Compare the curve fo r diatomaceous e a rth w ith th a t of c e l i t e
in fig u re 3.
I t w ill be noted in the case of c e l i t e th a t a I to 3 m ixture
was not obtained in any of the samples taken but was approached in the
f in a l sample.
A ll th e samples taken were more hig h ly concentrated t Viat1 the
o rig in a l m ixture o f I to 3.
I t was presumed th a t the th e o re tic a l p o rtio n
o f the curve as continued from th e f in a l sample, would r i s e ab ru p tly in
view o f the fa c t th a t the g re a te r p o rtio n of sodium a rs e n ite had f a lle n out.
The two substances thus f a r considered have n e arly the same
d e n s itie s , and th ese d e n s itie s more n e arly approach th a t of sodium a rs e n ite
than any o f the o th er in e r t m a te ria ls used.
to Table IV.
This may be seen by refe ren c e
I f th e d en sity of the in e r t in g red ien t was the f a c to r in
—IS —
TABL3 111.-P ro p o rtio n s "by weight of the d ilu e n t to one p a rt of
sodium a rs e n ite as determined from samples c o lle c te d a t v arious d istan c es
from th e dust nozzle.
D istance
in fe e t
I
2
3
4
5
6
7
g
9
IO
ii
12
13
14
Diatomaceous
e a rth
1.52
0.55
0.49
0.71
0.97
2.21
1.20
1.83
1.03
—
3.04
8.11
9.12
12.90
C e lite
0.88
1.21
1.50
1.68
1.49
1.26
1.38
1.44
1.87
1.79
2.09
2.23
2 .6 l
2.62
Volcanic
ash
1.36
1.69 .
2.38
3-55
4.32
4.16
4.21
3.84
4.02
3.54
3.36
3.12
2.76
2.36
Hydrated
lime
1.68
1.89
2.19
2.22
2. 26.
2.27
2.33
3.14
2.67
1.99
2.22
1.87
2.16
1.63
Benton­
ite
2.89
2.53
2.46
3.17
3-73
3.94
3.84
3.71
3.71
3.47
3.63
3.57
4.12
3.53
Calcium
carbonate
0.90
0.97
0.91
1.83
2.88
3.57
4.73
4.23
4.39
4.32
4.37
4.20
4.01
4.03
TABLE IV.-Some p h y sic al a sp ects of the d ilu e n ts used.
M aterial
Sodium A rsen ite
Diatomaceous E arth
C e lite
Hydrated Lime
B entonite
Volcanic Ash
Calcium Carbonate
Degree o f Subdivision
- Very fin e
M oderately fin e
Very fin e
Very fin e
M oderately coarse
Coarse
M oderately fin e
Density
1.87
I .96
1.99
..........
2.20
2.49
2.59
2.70
determ ining i t s so -c a lle d carry in g p ro p e rtie s , one might then expect to
o b tain a s tr a ig h t lin e , or n early so, superimposed on the h o riz o n ta l lin e
which re p re se n ts a I to 3 m ixture in fig u re s 2 and 3*
I t i s obvious th a t
th is type o f curve was not obtained in e ith e r th e case o f diatomaceous
e arth or c e l i t e .
-
EARTH
OIAfOMACEOUS
HYDRATED LIME
VOLCANIC
AS H
PROBABLE
CONTINUANCE
OF
CURV E
PROPORTIONS BY WEIGHT OF SODIUM
A R SEN ITE
TO DILUENT
” 19"
D IS T A N C E
IN
FEET
FROM
DUST
NO ZZLE
JFigare 2. S e ttlin g curves fo r diatomaceous e a rth , hydrated lim e,
and v olcanic ash.
PROPORTIONS BY WEIGHT OF SODIUM ARSENITE TO DILUENT
«»20**
CEUTC
BENTONITE
CALCIUM CARBONATE
PROBABLE
D IS T A N C E
IN
CONTINUANCE
FEET
FR O M
OF
DUST
CURVES
12
NOZZLE
IS
14
Figure 3» S e ttlin g curves fo r c e l i t e , b e n to n ite , and
calcium carbonate.
16
■
' f- • '%
M
V "
. - : '! - V 1W
'>
;
C-
•.
.■
; v
••*
»
*;• - ,
.. V
rt
•
e
'■
# >'
"
D i
^
♦ x>V •
,
V i^
O v1°- '
'
• « »
v
-. - V
VI
C e lite
Diatomaceous earth
- ^v
i
*?t i t
«f
V »
'
>*-
' -
:>
V - V >.
.
> r 4*
-J - V
- v > .
»* A ' ^
*
*•:
*.o
•
>
V \
I •'
v : >.:
-
•
^
#
Calci-ain carbonate
* ■ <.• > „ W
%4 .
-
IBlIi
I
fig u r e 4 .
'
- :
, -
B en to n ite
V .-.’
"
• *
x
. : • :•
• ••
..
. V V *: V V
V olcanic ash
V
•
.‘ V
•’. 2 W f U '.<
** J
,
*
•
-
>• •• •
, •'
» «.
> ’
.
■
•
<
, •■
V
.Vi -;
V
*• ^ •
•'
•
/ f :
Im
•
*♦. *
' X
I
>
I .
f.
;
> * .
Hydrated l i n e
; hotom icrographs o f the d ilu e n ts .
•
•
'
•
»•
. », -
-2 2 -
Consider the photomicrographs of these two substances in
fig u re 4.
I t w ill be noted th a t both substances contain ir r e g u la r
p a r t i c l e s of somewhat sim ila r p a tte r n .
s iz e , both appear to be somewhat a lik e .
With th e exception o f p a r t i c l e
The p a r t i c l e s composing
diatomaceous e a rth a re la rg e and many of them f l a t , w hile those of c e l i t e
a re considerably sm aller and le s s f l a t in c h a ra c te r.
Both substances appear
extremely lig h t and f lu f f y under a b in o cu lar m icroscope.
R eferring again
to the curves of th e two substances in fig u re s 2 and 3, i t would appear th a t
the la rg e r f l a t p a r t i c l e s of diatomaceous e a rth were blown ab ru p tly away
from th e sodium a rs e n lte p a r t i c l e s fo r a sh o rt d istan c e from the nozzle.
The rem ainder of the dust cloud p a s t the
fo o t p o in t was consequently
composed la rg e ly of in e r t m a te ria l which then s e t tl e d o u t.
In the case of
the s m a lle r,le s s f l a t p a r t i c l e s of c e l i t e , the curve in d ic a te s th a t these
p a r tic le s a lso blew away from the sodium a rs e n lte but d id so le s s ra p id ly
and s e ttle d out more uniform ly.
Before comparing the curves fo r b e n to n ite and volcanic ash, fig u re s
2 and 3, a d e sc rip tio n o f th ese m a te ria ls w ill be given.
B entonite, a fin e ly
divided c lay , was obtained in the v ic in ity o f Hardin, Montana, and volcanic
ash, a f in e ly divided product co n tain in g a high p er cent of s i l i c a , was
obtained near Big Timber, Montana.
Both substances have d e n s itie s very much
a lik e , and t h e i r d e n s itie s a re h a lf again g re a te r than those o f e ith e r c e l i t e ,
diatomaceous e a rth , o r sodium a rs e n lte .
With refe ren c e to fig u re 4, i t w ill
be seen th a t v o lcanic ash i s composed of extrem ely coarse san d -lik e
p a r t i c l e s , ir r e g u la r in siz e and shape.
The b e n to n ite , while only m oderately
co arse, i s a lso composed o f ir r e g u la r p a r t i c l e s s lig h tly le s s angular in
-2 3 -
ch arac ter than v olcanic ash.
I t w ill he noted th a t th e re i s a c e rta in s im ila rity in th e two
curves.
Both r i s e abru p tly between 3 and 6 f e e t from the dust nozzle and
then ten d to approach the I to 3 m ixtures.
I t would appear from the curve
fo r volcanic ash th a t the la rg e heavy p a r tic le s of th is m a te ria l a re blown
out away from the sodium a rs e n ite p a r tic le s only a very sh o rt d ista n c e .
The abrupt r i s e of the curve from the 3 foot p o in t to a co n cen tratio n of
approxim ately I to 4.5 sodium a rs e n ite to volcanic ash in d ic a te s a d ilu te
d u st.
Within th is p o rtio n o f the curve the in e r t m ate ria l s e t t l e s out q u ite
ra p id ly .
At a p o in t 12 fe e t from the nozzle, a I to 3 m ixture again occurs.
Prom here on out a concentrated m ixture i s obtained, due to the fa c t th a t
the g re a te r p o rtio n o f in e r t m a te ria l has s e t tl e d out before reaching th is
p o in t.
The curve fo r the somewhat more f in e ly d ivided b e n to n ite follow s
the same general tre n d as th a t of v olcanic ash.
However, a f t e r the abrupt
r i s e th e curve does not descend as ra p id ly as th a t o f the form er.
This
in d ic a te s th a t a more uniform s e t tl i n g out o f the i n e r t m a te ria l occurred
than in the case o f the la rg e r p a r t i c l e s of volcanic ash.
Now consider the s e t t l i n g curve fo r calcium carbonate as shown
in fig u re 3.
This m ateria l has the g re a te s t d e n sity o f any of th e i n e r t
m a te ria ls under t r i a l .
I t i s composed of m oderately f in e , re g u la r, non-
angular p a r t i c l e s , and as shown in Table IV i t i s more f in e ly divided than
volcanic ash or b e n to n ite , which a lso have high d e n s itie s .
Prom a study
o f the curve fo r calcium carbonate, i t w ill be seen th a t the m oderately
fin e p a r tic le s of th e in e r t m a te ria ls a re blown away from the sodium
a rs e n ite fo r a d istan c e of approxim ately 4& f e e t.
The samples obtained
-2 4 -
show a I to 3 m ixture a t about 5 f e e t from the nozzle.
I t may he seen
th a t the maximum s e t tl i n g out o f in e r t m ate ria l was somewhat f a r th e r from
the nozzle than i t was in e ith e r th e case o f volcanic ash or b e n to n ite .
The degree of subdivision of th e p a r tic le s i s h e ld re sp o n sib le fo r th is
occurrence in view of the fa c t th a t th e calcium carbonate i s h eav ier than
e ith e r o f the two above mentioned d ilu e n ts .
14 fe e t from the nozzle were very d ilu te .
A ll samples obtained from G to
In view o f t h is f a c t, the
th e o re tic a l p o rtio n of the curve i s presumed to again approach a I to 3
m ixture.
The l a s t s e ttlin g curve to be considered i s th a t o f hydrated lim e.
This substance c o n sists of very f in e ly divided, re g u la r, non-angular
m a te ria l s lig h tly h eav ier than sodium a rs e n ite .
Ifydrated lime appears to
agglomerate somewhat and in doing so gives the m a te ria l the appearance of
being composed o f about an equal number o f very fin e and m oderately fin e
p a rtic le s .
The form ation of th ese agglom erations lead s to a p o ss ib le
explanation o f the curve as shown in fig u re 2.
This curve more n e arly approaches what may be considered the
id e a l curve, a s tr a ig h t lin e superinposed on th e h o riz o n ta l l i n e re p re se n t­
ing a I to 3 m ixture, than any o f the o th er curves in fig u re s 2 o r 3.
Since the hydrated lime i s somewhat h eav ier than sodium a rs e n ite ,
i t may be presumed th a t as th e dust leaves the nozzle the la rg e agglom erates
o f in e r t m ate ria l begin s e t tl i n g out sim ultaneously w ith th e sodium a rs e n ite .
The sm aller p a r tic le s of lime a re then blown f a r th e r out from the nozzle
and do not begin s e t tl i n g out u n t i l most o f the la rg e agglom erates have
s e ttle d .
The sm aller p a r t i c l e s then s t a r t s e t tl i n g out a t about th e same
r a te th a t the la rg e r p a r t i c l e s had p rev io u sly s e t tl e d o u t, thus keeping the
-2 5 -
samples ra th e r uniform .
Throughout the e n tir e curve i t may he seen th a t
the sodium a rs e n ite s e t tl e d out o f the dust cloud s lig h tly f a s te r than did
the i n e r t in g re d ie n t.
I t i s presumed th a t the th e o re tic a l p o rtio n o f th e curve would
r i s e above th e I to 3 base lin e a t some p o in t p a s t th e p lac e where the l a s t
sample was taken.
This r is e may be a ttr ib u te d to the fa c t th a t a la rg e
p ro p o rtio n o f the samples were more concentrated than th e o rig in a l I to 3
m ixture, and a cloud of very f in e ly divided lime was suspended in th e a i r
p a st the 14 foot p o in t.
I t may be seen by a co n sid era tio n of the e n tir e s e rie s o f
s e t tl i n g curves th a t th e p ro p o rtio n of sodium a rs e n ite and i n e r t in g re d ie n t
does not remain the same throughout th e whole o f the dust cloud.
The
sodium a rs e n ite and the in e r t in g re d ie n t ap p aren tly s e t t l e out independently
o f each o th e r, thus showing the i n e r t substance to a c t so le ly in the ro le
o f a d ilu e n t.
I t i s apparent th a t the d en sity of the d ilu e n t does have some
e ffe c t on the a b i l i t y o f i t s p a r t i c l e s to sta y in suspension in a i r .
It
i s b eliev ed , however, th a t the p r in c ip le fa c to r in determ ining the un ifo rm ity
of a dust cloud i s th e degree o f subd iv isio n o f the p a r t i c l e s .
Under c e rta in
co n d itio n s, then, one may expect to o b tain what i s considered to be a
le th a l dust in th e case o f diatomaceous e a rth only about as f a r from the
dust nozzle as the s tr a ig h t sodium a rs e n ite could be blown.
JAEHING
eitscts on mixed dusts
Tables V and 71 embody the r e s u lts o f experiments which arose from
-2 6 -
the need to determine the e ffe c t on the co n cen tratio n o f the d u sts while
trucking drums of the mixed substances from a c e n tra l mixing s ta tio n to
f i e l d s ta tio n s .
Some workers in th e f i e l d have presumed th a t the dust taken
from the top o f the drum was more d ilu te than th a t obtained from near the
bottom.
An apparatus was c o n stru cted to as n e a rly sim ulate the ja r r in g
a c tio n of a moving tru ck as was p o s s ib le .
manner.
I t was made in the follow ing
A 5 fo o t board was mounted on a p latfo rm , hinged a t one end, and
re s te d on a p iec e of rubber sponge a t th e o th er end.
An e le c tr ic motor
equipped w ith a hardwood e c c e n tric wheel a tta c h e d to the sh a ft was b rack et­
ed to the p latfo rm .
The e c c e n tric wheel was allow ed :to r e s t on th e upper
side o f the board w ith s u f f ic ie n t p re ssu re to cause a s lig h t compression
of th e rubber sponge.
A sharp) ja r r in g motion was obtained with each
rev o lu tio n o f the wheel.
d e sired .
The speed of the motor could be reg u la te d as
U prights, to which two s e t tl i n g tubes 4 fe e t long and 5 cm. in
diam eter could be secu rely clamped, were a tta c h e d to th e board.
The s e t tl i n g tubes were f i l l e d to a h e ig h t of 2 f e e t w ith a
3 -to I m ixture o f th e d u sts, and th e samples removed from the bottom o f the
column a t.t h e time in te rv a ls noted i n Table V.
Two d ilu e n ts , one very dense
and the o th er very lig h t were used, and the experiments done in d u p lic a te .
I t w ill be noted th a t no ap p reciab le change in concen tratio n was
found in any samples obtained even a f t e r ja r r in g had been continued fo r
one hour.
Table VI shows the r e s u lts o f t i t r a t i o n s as obtained when I gram
samples of dust were taken from th e top of a column o f dust a f t e r ja r r in g
fo r the time I n te rv a ls noted.
The same apparatus and d u sts were used in
-2 7 -
TABLE V .-P roportion "by weight o f th e d ilu e n t to I p a r t o f
sodium a rs e n ite as determined from samples taken from the bottom o f a
column o f dust a f t e r v ib ra tio n fo r the time in te r v a ls noted.
Time in
minutes
5
10
15
20
25
30
35
4o
50
6o
P roportions by weight o f d ilu e n t to I p a rt sodium a rs e n ite
Diatomaceous e a rth
Volcanic Ash
Sample I
Sample 2
Sample I
Sample 2
3-1
2.9 "
3-1
2.9
3.1
3.0
2.9
2.8
2.8
2.8
2.7
2.7
2.6
3.0
2.9
2.8
2.8
2.7
2.7
2.7
2.6
2.6
2.9
2.9
2.9
2.9
2.9
2.8
2.8
2.8
3-9
2.7
2.8
2.8
2.6
2.8
TABLE 7 1 .-P ro p o rtio n by weight o f the d ilu e n t to I p a rt of
sodium a rs e n ite as determined from samples taken from th e top o f a cdlumn
o f dust a f t e r v ib ra tio n fo r the time in te rv a ls noted.
Time in
minutes
- 15
%
%
6o
P roportions by weight o f d ilu e n t to I p a rt sodium a rs e n ite
DiatomaceousI e a rth
Volcanic ash
Sample I
Sample 2
Sample I
Sample 2
3.1
2-3
3.4
2.0
2.7
3.1
3.5
3.6
3-3
2.7
1.9
2.5
3-4
3.2
3.1
3.0
th is experiment as were used in the previous experiment except th a t l i t e r
beakers were s u b s titu te d fo r th e s e t t l i n g tubes.
I t w ill be noted th a t the r e s u lts obtained in th is experiment
-2 8 -
were somewhat more e r r a tic than those of the previous one.
However, the
samples from th e top o f the c o n tain ers a f t e r prolonged ja r r in g show no
tendency to "become e ith e r more concentrated or more d ilu te to any g rea t
e x te n t.
-2 9 -
S3C1I0N II
PEEmBILIIY MD ITS COUTEOLLING FACIOBS
In in tro d u cin g th e problems considered in the follow ing se ctio n
o f t h is paper, i t i s deemed a d v isab le to e n te r in to a b r i e f d iscu ssio n o f
some o f the p o ss ib le fa c to rs which may in flu en ce the r e s u lts obtained.
I t i s g e n erally recognized th a t an in s e c tic id e , to e x h ib it to x ic
e f f e c ts , must e n te r the c e l ls o f the in s e c t.
Ihe foregoing statem ent
a p p lies to the so -c a lle d stomach poisons as w ell as to th e contact poisons.
I f the w alls of the alim entary t r a c t did not perm it the to x ic m ateria l to
e n te r the c e l l s , th e m a te ria l would be expected to p ass through th e in s e c t
with no in ju rio u s e ff e c ts .
For in sta n c e , arsenious sulphide, a hig h ly
in so lu b le but to x ic m a te ria l, when adm inistered as a stomach poison,
e x h ib its no to x ic e ffe c ts whatever.
A lso, a rs e n ic , when used as an i n s e c t i ­
c id e, i s known to a tta c k the nervous system of th e in s e c t.
T herefore, i t
must en te r the c e l l s , as the nervous system i s not b e lie v e d to be exposed,
e ith e r on the ou ter su rface or in th e alim entary t r a c t o f the in s e c t.
If
the nervous system were exposed the m a te ria l would s t i l l have to p e n e tra te
a c e l l membrane in order to e n te r.
A ll p erm e ab ility c o n tro l i s presumed to l i e p rim a rily in the o u te r
plasma membrane of the c e l l .
The follow ing i s a l i s t of some of th e fa c to rs
which a re thought to in flu en ce the p erm e ab ility e ith e r a c tin g c o lle c tiv e ly
o r sin g ly ; chemical c o n s titu tio n , pore s iz e , e le c t r i c charge, surface
ten sio n , a d so rp tio n , hydrogen ion c o n cen tratio n , age and p h y sic al co ndition
o f tis s u e , presence o f s u f f ic ie n t m oisture fo r so lu tio n and io n iz a tio n of
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the le th a l m a te ria l, and tem perature.
Consider surface te n sio n alone and the numerous fa c to rs which
might in flu en ce i t .
The suggestion has been made hy S e ifriz (7) th a t a
high surface ten sio n would p re se n t an i n te r f a c ia l membrane made up of
tig h tly packed molecules between which substances could not p ass re a d ily .
Low surface ten sio n would mean a loose arrangement o f surface molecules and
th e re fo re a more permeable membrane.
Hydrogen ion c o n cen tratio n may a lso be considered.
I t has been
shown th a t the hydrogen ion co n cen tratio n both o f the c e l l contents and o f
th e surrounding m a te ria l has a d e fin ite in flu en ce on the p erm e ab ility o f
th a t membrane, both to substances p assin g in and p a ssin g out o f the c e l l .
S e if r iz (7) s ta te s th a t experim ental evidence is a v a ila b le which shows
th a t in some cases sodium ions w ill e n te r the c e l l more ra p id ly in an a c id
medium than in an a lk a lin e one, and th a t th e speed a t which th ese ions e n te r
in c re a se s w ith a corresponding in c re a se in a c id ity .
Unpublished d a ta by
J . H. Pepper and th e author show the pH of the re g u rg ita te d d ig e s tiv e
Ju ices o f Mormon c ric k e ts to be 4.53 and th a t th ese d ig e s tiv e ju ic e s a re
h ig h ly b u ffered both on the a c id and a lk a lin e sid e .
In view of these
fin d in g s i t i s b eliev ed th a t the p e rm e ab ility of the c e l ls lin in g the
alim entary t r a c t would not vary g re a tly because o f pH changes even though
in s e c tic id e s o f stro n g ly a c id or b a sic c h a ra c te r a re in g este d .
Now consider the p o ss ib le v a ria tio n s in p e rm e ab ility which might
be brought about by d iffe re n c e s in age and h e a lth of the tis s u e .
Since
the process of aging i s accompanied by a lo ss in w ater content of the
protoplasm , i t i s o bvious-that o ld e r tis s u e containing le s s water i s more
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impermeable than th a t o f young tis s u e .
I t would then he suspected th a t in
an in s e c t such as the Mormon c ric k e t, th e e a rly in s ta r s would he much more
su scep tib le to a rs e n ic a l dusts than th e a d u lts .
Any abnorm ality in the
fu n ctio n in g of th e c e lls would he expected to in flu en ce the p erm eab ility
o f the protoplasm ic membrane.
I t w ill then be seen th a t a disturbance of
the normal co n dition due to e ith e r sickness or in ju ry would in a l l
p ro b a b ility render the tis s u e more permeable than th a t of a h e alth y
in d iv id u a l.
Experiments have shown th a t any abnormal co ndition of the c e l l
i s accompanied by a ra p id decrease in e le c tr ic a l re s is ta n c e w ith a
corresponding in c re a se in p erm e ab ility .
VARIA llOHS IH BIOLOGICAL MATERIAL
Keeping in mind the a b i l i t y of b io lo g ic a l m ateria l to e x h ib it
v a ria tio n s , exact d u p lic a tio n when u sin g th is m a te ria l should not be
expected in experim ental procedure.
Eor example, during p relim in ary
in v e s tig a tio n s in 1937. one l o t o f c ric k e ts c o lle c te d in th e same l o c a li t y
and tr e a te d ap parently in the same manner as a l l th e o th er l o t s , showed
100 p er cent m o rta lity a t a l l tem peratures in le s s time than th e lowest
which appears in Table V III a t JO0C.
unexplainable and u n p re d ic ta b le .
These v a ria tio n s a re as y e t la rg e ly
One may see re a d ily , to o , th e extreme
d if f ic u lty o f e ffe c tiv e ly c o n tro llin g a l l but a few o f the fa c to rs mentioned
which are thought to in flu en ce p e rm e a b ility .
With th ese p o in ts in mind,
the i r r e g u l a r i t ie s in the a c tio n o f sodium a rs e n ite d u sts which a re obvious
in the follow ing experiments should not be viewed w ith alarm .
Consider the
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v a ria tio n s in sep arate lo ts of immature c ric k e ts as apparent in Table V III.
In the two l o t s of 1 s t and 2nd i n s t a r in s e c ts , i t w ill he noted th a t a t
le a s t twice as f a s t a k i l l was o b tain ed a t a l l tem peratures w ith th e second
lo t than w ith the f i r s t .
Also compare the f i r s t l o t o f 1 st and 2nd in s ta r s
w ith th a t o f the second l o t o f 2nd and Jrd i n s t a r s .
I t w ill he noted th a t
in some cases four times as- quick a k i l l was obtained w ith th e l a t t e r than
w ith the form er.
Temperature changes in a cold blooded animal such as the Mormon
c ric k e t, a ff e c t a number of the v a ria b le fa c to rs form erly mentioned, such
as su rface ten sio n , ad so rp tio n , s o lu b ility , and io n iz a tio n .
For t h is reason
tem perature changes a re given p a r tic u la r co n sid era tio n in t h is paper even
though time may prove them to be le s s im portant than some of the o th er fa c to rs .
i
THE ACTION OF DUSTS WHEN APPLIED TO VARIOUS
REGIONS OF THE INSECT BODY
Table V II, rep resen ted g ra p h ic a lly in fig u re 5, shows th e r e s u lts
obtained from stu d ie s of the a c tio n o f sodium a rs e n ite dust when a p p lied
to d iffe re n t p a rts of th e body o f a d u lt c ric k e ts .
A 3 to I m ixture o f
hydrated lime and C.P. meta sodium a rs e n ite , NaAsO2. was used, and constant
tem perature and r e la tiv e hum idity were m aintained throughout th e e n tire
s e r ie s .
A c o lla r was devised (see fig u re 6) to prevent the c ric k e t from
cleaning any p o rtio n of i t s body, thus preventing any in tro d u c tio n o f to x ic
m a te ria l in to the alim entary t r a c t .
In a d d itio n , a la rg e p ro te c tiv e sh ie ld
through which the a n te r io r p o rtio n o f the c ric k e t p rotruded was provided
TABLE VII . -P er cent m o rta lity f o r c ric k e ts dusted w ith a 3 to I
m ixture of hydrated lime and sodium a rs e n lte a t 36° C. and 50$ r e la tiv e
hum idity, showing th e a c tio n of th e dust when ap p lied to d iff e r e n t p a rts
o f the c ric k e t.
Time in
hours
3
4
5
6
8
10
12
14
16
18
20
With c o lla rs
2.5
11.0
25.0
45.0
81.0
92.0
95.0
P er cent M o rta lity
Without c o lla rs
T arsi dipped
2.5
8.0
20.0
37.0
66.0
85.0
97.0
.
0.0
0.0
0.0
10.0
25.0
44.o
58.0
71.0
78.0
84.0
87.0
during d u stin g operations to prevent any d ire c t a p p lic a tio n o f dust to the
head and mouth p a r ts .
Each c ric k e t was dusted se p a ra te ly w ith as uniform
a coating o f dust as was p o ss ib le and p laced in the tem perature c a b in e t.
Five l o ts o f twenty each were tr e a te d in t h i s manner and the average p e r
cent m o rta lity computed.
Undusted check l o t s both with and w ithout
c o lla r s showed no m o rta lity in tw enty-four hours.
Jiv e l o t s of twenty each were dusted over th e ir e n tir e body
surface and placed in th e tem perature cabinet along w ith an equal number
whose t a r s i only were dipped in the d u st.
The c ric k e ts whose movements were not hampered by c o lla r s began
cleaning themselves imm ediately.
Ho p a rt of t h e i r body which could be
---- O COMPLETELY DUSTED
— o WITH COLLARS
•—Q TARSI DIPPED
PERCENT
M O R T A L IT Y
z— ,
TIME
IN
HOURS
Figure 5« K o rte lity curves fo r various methods o f applying d u sts.
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'i\
fig u re 6. Korznon c ric k e t shoeing c o lla r
a ttach ed .
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reach ed was neglected; t h e i r antennae, t a r s i , le g s , v e n tra l sid e o f the abdomen,
as w ell as t h e ir o v ip o sito rs and c la sp e rs were a l l cleaned.
In each o f th e
th ree types of trea tm e n t, the f i r s t symptom o f e ff e c t from the poison was
m anifest in a g eneral lo s s of co o rd in atio n , follow ed then by a more severe
p a ra ly s is w ith considerable re g u rg ita tio n of d ig e s tiv e Ju ic es and d eposition
o f fe c a l m a te ria l.
Succeeding th is stage th ere appeared to be very l i t t l e
movement except fo r spasmodic tw itc h in g s.
Ihe c ric k e ts were considered dead in
a l l the follow ing experiments when th ese spasmodic movements could no
longer be induced by g e n tle prodding.
I t w ill be noted by refe ren c e to fig u re 5 th a t much the same e f f e c t,
both in time and percentage k i l l , was obtained from th e dust when i t was
allowed to a c t e ith e r as a con tact poison ( c o lla r s attach ed ) or as both a
co n tact and stomach poison (no c o lla r s a ttac h ed to prevent in g e s tio n o f
d u s t) .
This in d ic a te s th a t th e sodium a rs e n lte dust was e ffe c tiv e in e ith e r
mode o f e n try .
I t fu rth e r in d ic a te s th a t the le t h a l m a te ria l could p e n e tra te
the lntersegm ental membranes of th e exoskeleton as w ell as i t could the
tis s u e c o n s titu tin g th e alim entary c an a l.
By refe re n c e to fig u re 5 i t w ill
a lso be noted th a t in the case of those c ric k e ts whose t a r s i only hpa been
dusted, th e time fo r an equal percentage m o rta lity was g re a tly in creased ,
as compared to the o th er two methods o f a p p lic a tio n o f d u st.
the u ltim a te m o rta lity was somewhat lowered.
In a d d itio n ,
O bservations show th a t the
c ric k e ts do not a l l begin cleaning t h e i r foot p a r ts immediately a f t e r dust­
ing when only the foot p a rts have been dusted.
On th e b a s is of th ese fin d in g s i t i s b eliev ed th a t the f i e l d
p r a c tic e , whereby dust b a r r ie r s a re l a i d down in the p ath s o f bands of
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c ric k e ts
should not "be expected to be too su c c e ssfu l.
A sh o rt d istan ce
tr a v e l by the band o f c ric k e ts over v eg etatio n and e a rth would in a l l
p r o b a b ility brush o f f a la rg e p o rtio n of the dust which the t a r s i had picked
up in cro ssin g the dust b a r r i e r .
There i s a lso the obvious danger to liv e ­
stock where th ese heavy co n cen tratio n s o f a rs e n ic a l d u sts a re l e f t exposed.
When dust b a rr ie rs a re used in connection w ith furrows wherein th e dust
i s p laced in the bottom o f th ese depressions, the case i s somewhat d iffe re n t
The in s e c ts u su a lly become dusted over a la rg e p o rtio n of t h e i r body e ith e r
when e n te rin g th e furrows or upon leaving i t , due to f a l l in g down the sid e
w a lls.
The furrow may then be e a s ily f i l l e d w ith e a rth to elim in ate danger
to liv e s to c k .
Schweis and Burge ( 6) s t a te th a t lime and sodium a rs e n ite s e t up
an i r r i t a t i o n causing the c ric k e t to attem pt clean in g i t s antennae and fo o tp a r ts and th a t m oisture in th e atmosphere appears to in c re a se e ffe c tiv e n e ss
o f th e poison, apparently in c re a sin g i t s I r r i t a t i n g q u a lity .
O bservations
have been made by the author on th e a c tiv ity of c ric k e ts a f t e r they have
been dusted w ith lime and sodium a rs e n ite dust and h e ld under d iffe re n t
con d itio n s of tem perature and hum idity.
These o bservations in d ic a te in
g en eral th a t the c ric k e ts begin imm ediately to clean them selves a t
tem peratures above 20eC. and continue to do so vig o ro u sly re g a rd le ss of
hum idity co n d itio n s.
At tem peratures under 20*0. they do very l i t t l e
"
clean in g o f dusted p a rts o f t h e i r b o d ies. O bservations by the author
,
a lso in d ic a te th a t under co nditions o f high hum idity quicker k i l l s are
o b tain ed .
I t i s b e liev e d th a t th e quicker e ff e c ts o f the dust under
co n d itio n s o f high hum idity i s not due to an In crease in i t s i r r i t a t i n g
—38q u a lity "but to the a d d itio n a l m oisture aid in g th e so lu tio n and io n iz a tio n
o f the sodium a rs e n ite .
In t h i s manner the l e t h a l substance i s believed
to be rendered more e ffe c tiv e .
TSIvlPSBAIUHS EFFECTS OU ACTION OF. DUSTS
Previous statem ents have been made concerning the p o s s ib i l i ty of
tem perature changes a ffe c tin g m o rta lity when u sin g a rs e n ic a l d u sts.
Table V III,
re p re se n te d g ra p h ic a lly by fig u re 7 . embodies th e r e s u l ts obtained from th e
follow ing experiments which were planned to study th ese tem perature e ff e c ts
on m o rta lity through each in s t a r up to and in cluding the a d u lt c ric k e t.
Chemically pure meta sodium a rs e n ite , UaAsO2. and diatomaceous
e a rth in the p ro p o rtio n o f I to 3 mere used in the e n tir e s e rie s of
experim ents.
A d usting chamber, see fig u re 8 , was co n stru cted to in su re
reasonably uniform d usting of th e sep arate l o t s .
a p p lie d to each l o t in the follow ing manner.
One gram of mixed dust was
Four hundred f i f t y to fiv e
hundred c ric k e ts were c h ille d fo r a few minutes a t a tem perature o f
approxim ately 36*F. to prevent any cleaning process u n t i l put in c a b in e ts,
p la c e d in the d u stin g chamber, and dusted w ith the one gram of d u st.
They
were then c h ille d again, sep arated in to four l o t s o f one hundred each, and
p lac ed in the various tem perature c a b in e ts.
The number o f dead c ric k e ts
and the time were noted a t re g u la r in te r v a ls and from th ese fig u re s the time
fo r a 50 p er cent m o rta lity was computed.
Check l o ts of c ric k e ts were tre a te d in the same manner as described
above w ith the exception o f d u stin g , and were p laced in each of the
-3 9 table
V III.-Tim e req u ire d fo r 50$ m o rta lity fo r th e various
nymphal in s ta r s and a d u lt c ric k e ts a t the tem perature noted.
Temperature
'
Average fo r
I n s ta rs
Average fo r
A dults
Time fo r 50% k i l l in Hours
30WC.
25” C.
20” C.
15” C.
5-0
1.5
3.0
1.5
2.0
3.5
8.5
5.5
5.0
4:0
2.0
6 .5
l.o
2.0
6.o
8.0
14".0
7.0
7.5
3-0
4.0
10.0
11.0
20:0
8.5
1 0 .5
6 .5
6 .0
12.5
is .5
20.0
6.o
1 3 .0
9 .0
1 2 .0
4.o
4.5
8.5
12.5
7.5
7.0
6.0
11.0
8.0
8.5
18.0
14.5
7.0
9 .0
17.0
tem perature c a b in e ts.
6 .5
1 9 .0
-
3 i.5
In s ta r
1 st
1 st
2nd
2nd
3rd
3rd
4 th
5th
6th
and
and
and
and
and
and
and
and
and
2nd
2nd
3rd
3rd
4th
4th
5th
6th
7 th
A dults
A dults
A dults
3 i.5
Ho m o rta lity was noted o th er than th a t caused by
a c tiv e c ric k e ts a tta c k in g and devouring those which were m oulting.
I t w ill he seen hy re fe re n c e to fig u re 7 th a t a d e fin ite decrease
in time fo r a 50 p e r cent k i l l was obtained, both fo r the nymphal in s ta r s
and a d u lts , w ith a corresponding in c re a se in tem perature.
T h is,th e n .
In d ic a te s th a t some fa c to r or fa c to rs which a re in flu en ced by tem perature
may be considered to p lay an im portant p a rt in e ith e r in c re a sin g or
d ecreasing the p erm eab ility o f the tis s u e s w ith re sp ec t to sodium a rs e n ite .
As was to be expected from previous statem ents, a t a l l
-U o -
IN S T A R S
25
TEM PERATURE
IN
C?
n s o r e 7. m o rta lity curves fo r a d u lt and immature c ric k e ts .
-Ul-
Figure S. Dusting chamber.
tem peratures t r i e d th e time re q u ire d to k i l l f>0 p er cent of the immature
c ric k e ts was considerably le s s than the time re q u ire d to k i l l 50 p e r cent
of the a d u lts .
Further c o n sid eratio n of fig u re 7 w ill show th a t a decrease in
tem perature appears to have a g re a te r e ffe c t on the time fo r a 50 p e r cent
k i l l in the case of a d u lts than in the case of th e nymphal i n s ta r s .
This may
he due to a g re a te r decrease in a c t iv i t y o f the a d u lts a t lower tem peratures
than o f the immature in s e c ts , or a decrease in p e rm e a b ility g re a te r in the
case o f the a d u lts than th e immature sta g es, o r to a combination o f these
or o th er f a c to rs .
In a l l p o s s ib i l i ty the a c t i v i t y f a c to r i s the most
im portant, since the small c ric k e t begins l i f e in the e a rly cool spring
tem peratures.
At t h is time p e rio d s of cold weather along w ith considerable
v a ria tio n s in tem perature may be expected.
I t would th e re fo re seem
reasonable to b e lie v e th a t th ese younger c ric k e ts were more a c tiv e a t the
co ld er tem peratures than the o ld e r ones which a re accustomed to warmer
summer tem peratures.
THS IKERT KATURS OF TES DILUENTS
The question has a ris e n as to whether or not any o f th e d ilu e n ts
a v a ila b le fo r use w ith sodium a rs e n ite would stim u la te or r e ta rd th e le t h a l
a c tio n of th is in s e c tic id e .
One to th re e m ixtures of sodium a rs e n ite and
the follow ing d ilu e n ts were used: hydrated lim e, c e l i t e , diatomaceous
e a rth , volcanic ash, calcium carbonate, and b e n to n ite .
An equal q u a n tity
by weight of each m ixture was dusted on l o ts o f 100 a d u lt crickets and th e
in s e c ts then placed In th e 25*0. tem perature c a b in e t.
P a rt o f th e s e r ie s
was rep eated fo r purposes of comparison.
I n s u f fic ie n t d iffe re n c e s in time fo r a 50 p e r cent 2d .l l (see
T alle IX) were considered to c o n s titu te proof o f the i n e r t q u a lity of a l l
the d ilu e n ts used.
In f a c t th e re was very l i t t l e d iffe re n c e in time fo r a
50 p e r cent k i l l considering the v a ria tio n s evident in the previous
tem perature stu d ie s .
TABLS IX.-Time req u ire d fo r 50$ m o rta lity u sin g equal q u a n titie s
of d u sts made up from d ilu e n ts as l i s t e d .
D iluent
Diatomaceous E arth
Hydrated Lime
Calcium Carbonate
C e lite
Volcanic Ash
B entonite
Time in Hours fo r 50®
M o rta lity a t B1S0C.
T ria l I
T ria l 2
4.5
5.0
4.0
5.0
4.5
5.0
5.0
4.0
3.5
4.0
-
LENGTH OF TIME BUSTS MUST BEMAIN ON INSECT BODY
Wet, dewy mornings a t which time c ric k e ts a re handed c lo se ly
to g e th e r, thus making d usting easy, and frequent sp rin g ra in s in some
l o c a l i t i e s ' where c ric k e ts abound, have ra is e d th e question as to the len g th
of time sodium a rs e n ite dusts must remain on th e in s e c t to prove e ffe c tiv e .
The follow ing experiments were devised to provide some d e fin ite inform ation
on th e above problem.
Three hundred a d u lt c ric k e ts were dusted in the d u stin g chamber
-
44-
w lth a 3 to I m ixture of d ia t omaceous e a rth and chem ically pure meta
sodium a rs e n ite and then divided in to lo ts o f one hundred each.
One l o t
o f the c ric k e ts was placed in each o f th ree tem perature cab in ets to be h eld
a t 30* 25, and 20*0.
Ten c ric k e ts from each cabinet were washed immediately
a f t e r d u sting, p laced in re a rin g cans, and retu rn e d to t h e i r re sp e c tiv e
c a b in e ts.
A thorough washing was accomplished by means o f p la c in g the
c ric k e ts under running tap water s lig h tly below room tem perature.
Ten
c ric k e ts were removed from each of the cab in ets a t f i f t e e n minute in te r v a ls
fo r n in e ty m inutes, placed in re a rin g cans, washed, and re tu rn e d to the
c a b in e ts.
Time fo r 50 p e r cent m o rta lity was computed from the time the
dust was ap p lied .
Blank spaces appearing in Table X in d ic a te th a t a 50 p er cent
m o rta lity was not apparent in 24 hours.
I t was observed th a t those c ric k e ts
not dead in th a t time showed l i t t l e or no e ffe c t from th e poison.
TABLE X .- Time fo r 50 p e r cent m o rta lity a t th e various
tem peratures fo r c ric k e ts dustfed w ith a 3 to I m ixture of diatomaceous
e a rth and sodium a rs e n ite , th e dust being washed o f f a t the time in te r v a ls
noted.
Time of washing
in minutes
Time in hours fo r 50 p e r cent m o rta lity
a t the follow ing tem peratures
30*0.
_25»C.
20*0.
Washed immediately a f t e r dusting
15
3°
21.0
45
17.5
60
15.5
75
16.0
90
10.0
Not washed
6.5
-
22 h rs .
-
11.5
8.0
11.0
11.0
6.5
15
3
17
15
9.5
-4 5 -
Somewhat e r r a t ic r e s u l ts were obtained; however, th e d a ta show
th a t th e removal of the dust from the "body su rfa ce even a f t e r one and oneh a lf hours, slows down the time re q u ire d fo r 50 p e r cent m o rta lity (see
Table X).
Very l i t t l e d iffe re n c e i s n o tic ea b le in k i l l i n g tim e a t the
in te r v a ls between 45 and 90 m inutes.
From Table X i t i s evident th a t i f
the dust i s removed previous to between JO and 45 minutes le s s in ju ry to
c ric k e ts i s to be expected than i f th e dust was allow ed to remain on the
in s e c t body fo r a longer p e rio d .
WATER BARRIERS
Another question which has re c eiv e d some a tte n tio n in c o n tro l work
i s the p o s s ib ility o f c ric k e t bands advancing where a body of w ater, such as
a r iv e r or i r r ig a ti o n d itc h , must be crossed.
Large numbers o f c ric k e ts
have appeared on the south side of the Yellowstone R iver in Yellowstone
County, Montana, during the p a s t few y e a rs, w hile very few have appeared
n orth o f the r iv e r .
R esidents along t h is r a th e r la rg e sw ift-flo w in g r iv e r
have o ccasio n ally n o tic e d c ric k e ts which they b e lie v e d to have crossed from
the south side to th e n orth sid e o f the r iv e r .
In the lig h t of the follow ing work t h e i r id e n tif ic a tio n o f th ese
c ric k e ts as those which have cro ssed th e r iv e r , may be c o rre c t.
However,
i t i s b eliev ed th a t only a very sm all percentage o f those which entered
th e w ater would manage to reach the o th e r sid e .
O bservations show th a t
a f t e r one and o n e-h alf minutes on th e surface o f w ater, a la rg e p ro p o rtio n
o f th e c ric k e ts become in a c tiv e and tend to sin k and r i s e p e rio d ic a lly w ith
-4 6 -
a consequent in g e stio n o f a la rg e q u a n tity o f w ater.
I f the c u rre n ts in
the r iv e r were so th a t these c ric k e ts were c a rrie d acro ss and deposited
on the f a r shore, in a l l p ro b a b ility they would recover com pletely.
In
view o f the in a c tiv e condition of the c ric k e t, i t i s more reasonable to
b e lie v e th a t in a sw ift fibw ing r iv e r the in s e c ts would be c a rrie d many
m iles down stream being submerged p e rio d ic a lly , and th a t only a very few
a t the most would be deposited on the opposite shore out of the w ater f a r
enough to give them s u ff ic ie n t time to recover.
Laboratory observations
showed th a t where c ric k e ts were p laced on the su rface o f a la rg e v e sse l o f
w ater, a high percentage a f t e r becoming in a c tiv e did not recover when
removed from the water u n t i l a f t e r a number of hours.
Table XI shows the
m o rta lity which may be expected when c ric k e ts a re t o t a l l y submersed in
water fo r the time in te rv a ls noted.
I t w ill be seen th a t a f t e r eig h t
m inutes' submersion 50 p e r cent m o rta lity was obtained.
TABLE X I.-P er cent m o rta lity fo r c ric k e ts t o t a l l y immersed
in w ater a t 26*0. fo r th e time in te r v a ls noted.
Time in Minutes
1
2
4
6
2
12
P er Cent M o rtality
10
10
30
30
%
-4 7 -
SUMMABI
Sodium a rs e n ite used in c ric k e t c o n tro l i s produced fcy the
arsen io u s oxide-sodium hydroxide method.
To produce a d e f in ite product
hy t h is method, i t i s necessary to c a re fu lly c o n tro l the co nditions under
which the re a c tio n i s allowed to proceed.
I t i s "believed th a t the commercial
product now obtained i s made up of a m ixture of meta sodium a rs e n ite , se v era l
d e riv a tiv e s of pyro sodium a rs e n ite , and fre e arsen io u s oxide.
The
in s e c tic id a l value of arsenious oxide, as such, when p re se n t in c ric k e t dust
i s b eliev ed to be doubtful.
Uniform dusts were obtained from both a b a ll m ill and f i e l d mixer
a f t e r approxim ately ten m inutes' mixing tim e.
Longer p erio d s of mixing did
not improve the u n iform ity o f the d u sts s u f f ic ie n t to w arrant th is p ra c tic e .
When mixing very la rg e q u a n titie s of d u sts, f i f te e n m inutes'm ixing time is
recommended.
The follow ing m a te ria ls , hydrated lim e, b e n to n ite , calcium
carbonate, c e l i t e , diatomaceous e a rth , and volcan ic ash, when added to
sodium a rs e n ite , were found to a c t so le ly in th e fo ie o f d ilu e n ts .
Ko
in d ic a tio n s were obtained th a t th e re were any p h y sic a l or chemical
a ttr a c tio n s between the d ilu e n ts and sodium a rs e n ite .
The u n iform ity of
a dust cloud was found to depend la rg e ly on th e s ta te o f subdivision o f
th e p a r t i c l e s .
Other fa c to rs which could be c o rre la te d w ith th e r e s u lts
ob tain ed were d e n sity and shape o f the p a r t i c l e s .
Prolonged ja r r in g o f re c e p ta c le s co n tain in g mixed d usts d id not
a l t e r appreciably the co n cen tratio n e ith e r on th e top or bottom o f the
-4 8 -
c o n ta in e rs.
I t was concluded then th a t mixed d u sts could he tra n sp o rte d
from c e n tra l mixing s ta tio n s to f i e l d crews w ithout changing the uniform ity
o f the d u sts.
I t was proposed th a t an in s e c tic id e , to he e ff e c tiv e , must e n te r
the c e lls o f the in se c t re g a rd le ss o f i t s mode o f a p p lic a tio n .
Chemical
c o n s titu tio n , pore s iz e , e le c t r i c a l charge, su rface te n sio n , ad so rp tio n ,
hydrogen ion c o n cen tratio n , age, p h y sic al c o n d itio n , m oisture, and
tem perature were thought to in flu e n ce th e p erm eab ility of the ou ter plasma
membrane wherein p erm eab ility c o n tro l i s presumed to l i e .
I r r e g u l a r i t ie s in experim ental d a ta which a re obtained when
u sin g b io lo g ic a l m a te ria l a re to be expected, due to v a ria tio n s w ithin th e
organism i t s e l f and to the numerous u n c o n tro lla b le f a c to rs mentioned above.
In tr e a tin g Mormon c ric k e ts , sodium a rs e n ite d u sts were found to
be e ffe c tiv e when ap p lied e ith e r as p u rely con tact poisons or as a stomach
and contact poison combined.
Approximately th e same r e s u lts were obtained
both in time and percentage k i l l , thus in d ic a tin g t h a t .t h e le t h a l m a te ria l
could p e n e tra te the in tersegm ental membranes o f the exoskeleton as w ell as
i t could the tis s u e lin in g the alim en tary can a l.
The s im ila r ity o f the
tim es fo r a 50 p e r cent m o rta lity in d ic a te th a t a le th a l dosage could e n te r
th e tis s u e s from th e outer su rface of th e in s e c t as quickly as i t could
from the reg io n o f the alim entary t r a c t .
,
I t was concluded th a t th e presence o f a high r e la tiv e hum idity
enhances the k i l l i n g p ro p e rtie s o f c ric k e t d u sts.
This would decrease the
evaporation from th e su rface o f the membrane, thus in c re a sin g the amount o f
m oisture a v a ila b le fo r so lu tio n and io n iz a tio n o f the l e t h a l m a te ria l, in
-4 9 -
which s ta te th is m a te ria l i s b e liev e d to "be most e ffe c tiv e .
Oa the "basis o f k i l l s obtained from l o t s o f c ric k e ts whose t a r s i
only had been dusted, th e p ra c tic e of lay in g down dust b a r r ie r s on the
su rface o f the ground in the p a th s of moving bands o f c ric k e ts was d is­
couraged.
Dust b a r r ie r s when used in connection w ith furrows or trenches
a re thought to be much more e ff e c tiv e .
An in c re a se in tem perature was found to b rin g about a correspond­
in g decrease in time fo r a 50 p e r cent k i l l both in the case of nymphal
i n s t a r s and a d u lts .
Temperature changes were found to have a g re a te r e ffe c t
on the k i l l s obtained w ith a d u lts than w ith the immature sta g e s.
This
apparent tre n d was thought to be connected w ith the g re a te r a c t iv i t y o f the
immature stag es a t lower tem peratures.
Evidence was p resen te d to show th a t each o f the s ix d ilu e n ts
stu d ied were in e r t when used in connection w ith c ric k e t d u sts.
I f sodium a rs e n ite dust i s removed from th e su rface of c ric k e ts
p rev io u s to 4$ minutes a f t e r d u stin g , a co n sid erab le decrease in percentage
m o rta lity may be expected.
Even a f t e r n in e ty m inutes, the removal o f dusts
may in some cases double the tim e n ecessary fo r a 50 p e r cent k i l l .
Bodies of w ater, such as a r iv e r or la rg e i r r ig a ti o n d itc h , Tn^y
c o n s titu te a b a r r ie r which only a sm all percentage o f th e c ric k e ts are able
to cro ss.
In some cases where o b stru c tio n s such as driftw ood or brush a re
p re s e n t, a much la rg e r percentage of c ric k e ts may e ffe c t a c ro ssin g .
la rg e percentage o f c ric k e ts become in a c tiv e in le s s than fiv e m inutes
a f t e r being placed on th e su rface of a body of w ater.
A 50 p e r cent
m o rta lity may be expected a f t e r eig h t minutes* t o t a l submersion.
A
-5 0 -
HTSEATUEB CITED
(1)
B ales, I.W.
1936. C ricket c o n tro l in Washington.
916- 918 .
Jour. Econ. Ent. 29:
(2)
Cowan, P.T.
1929. L ife h is to r y , h a b its , and c o n tro l of th e Mormon c ric k e t.
U.S.D.A. Tech. Bui. N o .l6 l.
(3)
Glover, L.C.
1936. On the p e n e tra tio n of c e rta in a rs e n ic a l compounds in to
th e body of the American cockroach, P e rip la n e ta
atnerlcana (L ). Iowa S ta te Jo u r. S c !.11:57-59.
(4)
Mellow, W.J.
I 929. A comprehensive t r e a t i s e on in o rg an ic and th e o re tic a l
chem istry. Longmans, Green and Co. L td ., Hew York,
Vol. IX: 116-117.
(5)
1930.
O ffic ia l and T en tativ e Methods of a n a ly sis o f the
A ssociation of O ffic ia l A g ric u ltu ra l Chemists. Third
E d itio n , page 35»
( 6)
Schweis , Geo. G. and Burge, Lee M,
1935* Mormon c ric k e t c o n tro l in Nevada, 1935.
A gr., Reno, Nevada.
.
S ta te Dept, of
(7)
S e i f r iz , Wm.
1936. Protoplasm . McGraw-Hill Book Company, I n c ., New York C ity.
pp. 268- 291.
( 8)
Shotw ell, R.L. and Cowan, E.T.
1928. Some p relim in a ry n o tes on the use of sodium a rs e n lte
d u sts and sprays in the c o n tro l o f the Mormon c ric k e t
(Anabrus sim plex.R a id .). and th e le s s e r m igratory
lo c u st (Helanoplus a tla n ls R ile y ).
Jo u r. Econ. Ent.
21: 222- 230.
’