Tabanid vectors of the arterial nematode, Elaeophora schneideri in southwestern Montana
by Rolando Humberto Espinosa
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in
Biological Sciences
Montana State University
© Copyright by Rolando Humberto Espinosa (1987)
Abstract:
A survey of Tabanidae was done during 1984 and 1985 to determine the species acting as vectors of
the arterial nematode Elaeophora schneideri Wehr and Dikmans,1935 in southwestern Montana.
Tabanids were trapped with modified Manitoba traps in the Gallatin National Forest. Flies were kept
alive in a cooler, and transported to Bozeman for dissection. The head, thorax, and abdomen of each
tabanid was cut open and examined for larval forms of the arterial nematode. The ovaries were
removed,teased apart,and dilatations of the ovarioles recorded to determine parity. Intensity of fat
bodies present in the abdominal coelom was noted.
A total of 1122 tabanids was collected, representing thirteen species. Hybomitra osburni was the most
abundant species, 50.0%, followed by H, tetrica, 25.3% , and H.
rupestris, 19.5%. These three species comprised 95.0% of the total tabanids collected. Hybomitra
osburni emerged in late June with numbers peaking in late July. Hybomitra rupestris and H. tetrica
peaked shortly after emergence in early July. The latter species were rarely trapped after mid July.
Elaeophora schneideri larvae; were present in 0.8% of the tabanids dissected. Three first stage larvae
(L1) were recovered from H. osburni in 1984 and 51 larvae (L1 to L2 ) from H. rupestris and H. tetrica
in 1985. Percent infection of infected flies was 50.0% for H. tetrica, 37.5% for H. rupestris, and 12.5%
for H osburni. The latter two species. were new hosts records for Elaeophora schneideri.
Parity data, together with fat body intensities, suggested that H. osburni is an autogenous species and is
not a major vector of Elaeophora. The infection percentages and possible anautogeny of Hybomitra
rupestris and H. tetrica suggests that these species are involved in the transmission of the arterial
nematode in southwestern Montana. TABANID v e c t o r s ,o f
the
arterial
nematode
ELAEOPHORA SCHNEIDERI IN
■
SOUTHWESTERN MONTANA
by
Rolando Humberto Espinosa
A thesis submitted in partial fulfillment
of the requirements for the degree
of
Master of Science
in
Biological Sciences
MONTANA STATE UNIVERSITY
Bozeman, Montana
March .198 7
UAltt VlB.
ii
APPROVAL
of a thesis submitted by
Rolando Humberto Espinosa
This thesis has been read by each m e m b e r of the thesis
c o m m i t t e e and ha s b e e n f o u n d to be s a t i s f a c t o r y r e g a r d i n g
con tent, E n g l i s h usage, f o r ma t, ci t a t i o n s , b i b l i o g r a p h i c
style, and c o n s i s t e n c y , and is r e a d y for s u b m i s s i o n to the
College of Graduate Studies.
3-3
. C l!
I
Date
Chairperson, Graduate Comr tttee
Approved for the Major Department
Date
H e a d , Major Department
Approved for the College of Graduate Studies
3' Zu/
Date
Gr ad u a te Dean
iii
STATEMENT OF PERMISSION TO USE
In presenting this thesis in partial fulfillment of the
requirements
for
a
master's
degree
at
Montana
State
University, I agree that the Library shall make it available
to b o r r o w e r s u n d e r ru l e s of the Library.
from
this
thesis
are
allowable without
Brief quotations
special
permission,
provided that accurate acknowledgment of source is made.
Permission for extensive quotation, from or reproduction
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s c h o l a r l y purpos es.
A n y c o p y i n g or use of t he m a t e r i a l in
this thesis for financial gain shall not be allowed without
my written permission.
Signature
iv
ACKNOWLEDGEMENTS
I t h a n k D a v e Pa c of the M o n t a n a Fish, W i l d l i f e , and
Parks Department for his interest and
information provided
a b o u t the to p o g r a p h y , an d d e e r e c o l o g y of t h e s t u d y area.
Thanks to Mrs. Elsie Armstrong for granting access through
her ranch. Also, t h a n k s to N a n C h r i s t i a n s o n of the F o r e s t
S e r v i c e for p e r m i t s to u se N a t i o n a l F o r e s t la n d d u r i n g the
study.
T h a n k s are a l s o e x t e n d e d to Dr. Bob D a v i e s for his
cooperation. Dr. George Poinar for identifying the 'mermithid
n e m a t o d e , an d Dr. W i l l i a m T u r n e r for c o n f i r m i n g i n s e c t
identifications.
A sp e c i a l t h a n k s to the staff of the M o n t a n a St a t e
U n i v e r s i t y V e t e r i n a r y R e s e a r c h Lab for t h e i r support,
e s p e c i a l l y M e r r i e M e n d e n h a l l for p h o t o g r a p h i c work, Ga l e
Callis for preparing the "invisible" for sectioning and Dr.
David Worley for arranging financial support, his enthusiasm
and ai d t h r o u g h o u t e v e r y a s p e c t of the study. T h a n k s to Dr.
R o b e r t Mo ore , Dr. G e o r g e R o e m h i I d , an d Dr. J a c k C a t l i n for
their comments and time. Finally, thanks to David Harrison
for his ai d in the field, h a r d work, a n d hum or , d u r i n g the
1985 collecting season.
V
TABLE OF CONTENTS
PAGE
A CK NO WLE DGE MEN TS............................................. iv
LIST OF T A B L E S ................................................ vi
LIST OF F I G U R E S .................................
A B S T R A C T ................
vii
ix
INTRODUCTION.................................................... I
Elaeophorosis in M o n t a n a .................................... 4
MATERIALS AND M E T H O D S ....................................
7
Fly Su r v i v a l .......... . . ................................... 14
Tra pp in g..................................................... I5
Tabanid Dis se ct io n........................................ .16
R E S U L T S ..........................................................20
Seasonal Distribution of Tabanids .................
22
Fly Dissection and Recovery Of
Elaeophora sc hn eideri ...................................... 22
Recovery of Me rm it hid ae .................................... 2 9
Parity D a t a .................................................. 31
D IS CUS SI ON ........................ ’............................ 38
Species Composition of Tabanidae ........................ 38
Horse Flies and Elaeophora sc hn eideri.................... 39
Horse Fly Parity and Host Restriction. .................. .44
S UM MAR Y.....................................
49
REFERENCES CITED
52
vi
LIST OF TABLES
TABLE
PAGE
1.
H o r s e fly a n d dee r fly s p e c i e s c o l l e c t e d in
s o u t h w e s t e r n M o n t a n a , s u m m e r s I 984 a n d 1 9 8 5 .... 21
2.
H o r s e an d de e r fl y s p e c i e s e x a m i n e d for E l a e o p h o r a
s c h n e i d e r if s u m m e r s 1 9 8 4 a n d 19 8 5................ 28
3.
Horse fly species i n f e c t e d with
Elaeophora
s c h n e i d e r i , s u m m e r s 19 8 4 a nd 1 9 8 5 .......... ......29
4.
Measurements of Elaeophora schneideri larvae from
horse flies in southwestern Montana, s u m me rs 1984
and 1 9 8 5 ................... .............................. .29
5.
H o r s e and d e e r
fly
s p e c i e s' e x a m i n e d for
m e r m i t h i d n e m a t o d e s , s u m m e r s 1984 a n d 1 9 8 5 ..... 30
6.
Parity of three horse fly species dissected, summe r
1 9 8 4 ........... .................................. ....... 35
7.
Parity of three horse fly species dissected, s um me r
19 8 5 ............................................. . . ...... 35
v ii
/
LIST OF FIGURES
FIGURE
PAGE
I.
Study area in the Bridger Range, s u m me rs
1984 a n d
1 9 8 5 .......................................8
2.
Location of Manitoba fly traps in the Brackett
C r e e k , C a r r o l Creek, F a i r y Lake, a nd N o r t h
Cottonwood Creek
drainages
in the Bridger
Range, s u m m e r s 1984 a n d 1 9 8 5 ............... ..... 9
3.
Collecting area in the Rat Lake campground in
th e G a l l a t i n Range, s u m m e r 19 8 5 ................. 1 0
4.
Modified Manitoba fly trap used to collect horse
a n d d e e r f l i e s , s u m m e r s 1 9 8 4 a n d 1 985 .,...... 1 2
5.
Detailed vi ew of the collar, collecting fu nnel,
a l u mi nu m tube, wood dowel, and a t t a c h m e n t .to
the t r a p
c o l l a r ................... ............ '.... 13
6.
C r o s s s e c t i o n and l a t er al v i e w of a h o r s e fly
s h o w i n g the l o c a t i o n of the p l e u r a l m e m b r a n e ... 17
7.
Seasonal distribution of three horse fly species
c o l l e c t e d in the B r i d g e r R a n g e , s u m m e r 1985...-----23
8.
Seasonal distribution of three horse fly speciesc o l l e c t e d in the B r i d g e r Range, s u m m e r 198 4.... 24
9.
Early
first
stage
larva
of
Elaeophora
schneideri from a female Hybo m itra osburni,
s umme r 1 9 8 4 ............................................ 25
10.
F i r s t st a g e lar va of E l a e o p h o r a s c h n e i d e r i
f r o m a f e m a l e H y b o m i tra r u p e s t r i s ,
summer
1 9 8 5 .......................
26
11.
Second stage larvae of Elaeophora schneideri
f r o m a f e m a l e H y b o m itra t e t r i c a , s u m m e r
19 8 5 ................... .............................. 27
12.
M e r m i t h i d n e m a t o d e f r o m a f e m a l e H y b o tnitra
osburni,
summer
1 9 8 4 ..................
32
viii
LIST OF FIGURES
(continued)
FIGURE
13.
PAGE
Mermithid
os^burnd.,
n e m a t o d e f r o m a m a l e H y b o m itra
summer
1 9 8 5 ........................
14.
M e r m i t h i d ■n e m a t o d e f r o m a f e m a l e H y b o m itra
t e tr ica,
summer
1 9 8 5 ............................3 4
15.
Number
of
nulliparous
and
uniparous
individuals of three horse fly species trapped
in the summer of 19 8 5 .....................
33
37
ix
ABSTRACT
A survey of Tabanidae was' done during 1984 and 1985 to
d e t e r m i n e the s p e c i e s a c t i n g as v e c t o r s of the a r t e r i a l
n e m a t o d e E l a e o p h o r a s c h n e i d e r I W e h r and D i k m a n s 1 9 3 5 in
southwestern Montana. .
Tabanids were trapped with modified Manitoba traps in
the G a l l a t i n N a t i o n a l Forest. F l i e s w e r e k e p t a l i v e in a
cooler, and transported to B o z em an for dissection. The head,
t h o r a x , a n d a b d o m e n of e a c h t a b a n i d w a s c u t o p e n a n d
e x a m i n e d f o r larval f o r m s of t h e a r t e r i a l
ne m a t o d e . T h e
o v a r i e s w e r e r e m o v e d ,t e a s e d a p a r t , a n d d i l a t a t i o n s of the
o v a r i o l e s r e c o r d e d to d e t e r m i n e parity. I n t e n s i t y of fat
bodies present in the abdominal coelom was noted.
A to t a l of 1122 t a b a n i d s w a s c o l l ec te d, r e p r e s e n t i n g ■
t h i r t e e n species. H y b o m i t r a o s b u r n i w as the m o s t a b u n d a n t
species, 50.0%, f o l l o w e d by H, t e t r i c a , 25.3% , and H.
rupestris, 19.5%. These three species comprised 95.0% of the
total tabanids collected. Hy bomitra osburni emer ge d in late
June with numbers peaking in late July. Hybomitra rupestris
and H. tetrica peaked shortly after emergence in early July.
The latter species were rarely trapped after m i d July.
E l a e o p h o r a sc h n e i d e r i larvae; w e r e p r e s e n t in 0.8% of
the tabanids dissected. Three first stage larvae (L^) were
r e c o v e r e d f r o m H. o s b u r n i in 1984 a n d 51 l a r v a e (L^ to I^)
f r o m H. r u p e s t r i s an d H. t e t r i c a in 1985. P e r c e n t i n f e c t i o n
of i n f e c t e d fli es w a s 50.0%
for H. t e t r i c a , 37.5%
fqr H.
rupestris, and 12.5%
for H osburni. The latter two s p e c i e s .
were n e w hosts records for Elaeophora schneideri.
■P a r i t y data,
t o g e t h e r w i t h fat b o d y i n t e n s i t i e s ,
s u g g e s t e d t h a t H. o s b u r n i is an a u t o g e n o u s s p e c i e s a nd is
not a maj or vector of El^eophora. The infection percentages
and p o s s i b l e a n a u t o g e n y of
H y b o m itra r u p e s t r i s a nd H,
t e t r i c a s u g g e s t s t h a t t h e s e s p e c i e s are i n v o l v e d in the
t r a n s m i s s i o n of the a r t e r i a l n e m a t o d e in s o u t h w e s t e r n
Montana.
I
INTRODUCTION
Elaeophora schneideri Wehr and D i k m a n s , 1935 (N e m a t o d a :
O n c h o c e r c i d a e ) is a n e m a t o d e
that lives in
t he a r t e r i a l
s y s t e m of n a t i v e w i l d and d o m e s t i c r u m i n a n t s
mule deer,
white-tailed deer,
North America
domestic
sheep and goats)
(Adcock et a l . , 196 5 ; H i b l e r
1969,
1971;
Hibler and Adcock,
1971;
1972;
P r e s t w o o d an d R i d g e w a y ,
(elk, mo ose,
et a l .,
in
1968 ,
Anderson and Weinmann,
1972;
Worley
W o r l e y , 1975). O t h e r r u m i n a n t s p e c i e s
et al., 1972 ,
(sika deer, b a r b a r y
sheep and ibex)
introduced to North America also serve as a
definitive
for the arterial
1978;
host
Pence and Gray,
Elaeophora
mesenteric,
County,
nematode
1981; Hibler and Prestwood,
schneideri
was
originally
1981).
found
in
the
iliac, and carotid arteries of sheep from Catron
Ne w Mexico in 1933 (Kemper,
Dikmans of the
In dus try ,
(Robinson et al.,
1938). In 1935, Wehr and
Zoological Division of the Bureau of Animal
U.S.D.A., n a m e d
the
nematode
found
by
Kemper
Elaeophora schneideri in honor of Dr. F. L. Schneider of the
Field Inspection Division, Albuquerque,
Kemper's
initial
find
d i s c o v e r y of t h e a r t e r i a l
and
D i k m a n s , 1935).
personnel
observed
was
New Mexico.
followed
by
Huffman's
w o r m in m u l e d e e r in U t a h (W e h r
Arizona
blindness
Fish
of
and
Game
unknown
Department
etiology
in elk
2
from
1944 to 1961.
E v e n t u a l l y the a r t e r i a l n e m a t o d e
implicated as the causative agent
(Adcock et al.,
was
1965).
In N e w M e x i c o , the f i r s t r e c o r d of the a r t e r i a l w o r m in
elk wa s in 1964 (H i b l e r et al.,
19 6 9 ). E I a e o p h o r a
reported from mule deer in N e w Mexico
wa s n o t
until Hibler et
found the w o r m in mature mule deer in 1968,
al.
although reports
of the n e m a t o d e in m u l e d e e r in o t h e r s t a t e s a n d C a n a d a w e r e
confirmed prior to 1968
Flies
(Diptera)
(Hibler et al.,
belonging
1969).
to the
families
(horse and d e e r flies) and R h a g i o n i d a e
Tabanidae
(snipe flies)
were
found infected with a nematode that resembled E.. schneideri
(Hibler et al., 1969). Dissection of horse flies captured in
the Gila National Forest in Ne w Me xico permitted collection
of
the
infective
injected
adult E.
into
st ag es
mule
of
the
arterial
deer and d o m estic
schneideri from the arterial
confirmed the biological
incriminated horse
worm
sheep.
that
were
R e c o v e r y of
system of these hosts
cycle of the arterial nematode and
flies
as
the
natural
intermediate
host
(Hibler et al., 1970).
Hibler
Tabanidae,
et
Hybomitra
of the a r t e r i a l
Fprest
al.
identified
of E . s c h n e i d e r i
(19 71a)
sp. and Tabanus
worm.
the
fou-nd
Later
tetrica
r u b i l a t a , Tabanus
g i I anus
(Clark,
sp.,
genera
of
the
acting as vectors
s t u d i e s in t he G i l a N a t i o n a l
following
: H y b o m itra
two
tabanid
species
as
vectors
l a t i c o r n i s , H. p h a e n o p s , H.
a b d i t u s , T . e u r y c e r u s , and
T.
1972). At th e s a m e t i m e H. p r o c y o n a n d .T.
3
monoensis were incriminated as vectors of the arterial w o r m
in black-tailed
deer
in California
(Anderson
and
Weinmann,
1972).
Studies in Ve r m e g o Park, N e w Mexico showed four species
of
ho r s e
fl ie s
(H.
aatos,
T.
punctifer,
T.
s u b s i m i Iis
subsimilis and. T. st on i ) were naturally infected with larval
forms of E.
schneideri
Clinical
reported
(Davies,
elaeophorosis
from
Florida,
in
1979).
white-tailed
Georgia,
(Prestwood and Ridgeway,
1972;
and
deer
South
has been
Carolina
Hibler and Prestwood,
1981).
The i n t e r m e d i a t e ho s t s of E. s c h n e i d e r i and t he life cy c l e
were reconfirmed in South Island, South Carolina (Co uyilIion
et
a I.,
stages
19 8 4).
of
the
Tabanids
arterial
Tabanus 'lineola
found
worm
hin el lu s ,
and
infected
with
in
South
T.
nigrovittatus
th e
Carolina
larva l
included
(Co uvillion
et a I ., 19 8 4).
The pathogenesis
infected.
Kemper
of elaeophorosis varies with the host
(1938)
described
"filarial
dermatosis"
on
the poll of the h e a d in sheep, a n d D i k m a n s (19 4 8) r e p o r t e d
lesions
on domestic
sheep
caused by the
arterial
nematode.
Similar lesions described as "scabbing" were reported on the
face,
muzzle,
ears,
and crown of Barbary
l erv ia), an introduced species
Gray,
muzzle
sheep
(Am m o t r a g u s
from North Africa
(Pence and
1981). W i l d u n g u l a t e s in w e s t e r n s t a t e s s h o w m a r k e d
ne c r o s i s ,
blindness
ear
c r op pi ng ,
antler
(Jensen a n d S e g h e t t i , 1955;
deformity,
Hibler
and
a n d Adcock,
4
1970).
Reviews
present
in the
(Hibler
and
Prestwood,
of th e p a t h o g e n e s i s of e I a e o p h o r o s is
literature and will
Adcock,
19 7 1 ;
not
Davies,
be
are
repeated
19 79 ;
here
Hibler
and
1981)
Elaeophorosis in Montana
The first reported case of elaeophorosis in Montana was
from
Kalispell,
(Wilkins,
1951).
i m p o r t e d f r o m Id a h o w e r e f o u n d
Three
domestic
wi t h lesions
sheep
in th e poll
a r e a of the head. L a b o r a t o r y e x a m i n a t i o n of sk i n s c r a p i n g s
showed microfilariae present,
and the
description of
in
New Mexico
elaeophorosis
(Kemper,
In 1971,
matched
the
sheep from Catron County,
1938).
a moose was observed staggering and moving in
circles in the Boulder River drainage,
M on ta na .
lesions
Th e a n i m a l
died
in Sweetgrass County,
shortly after
W i l d l i f e b i o l o g i s t s a r r i v e d at the
Montana
sc e n e
Fi s h and
( W o r l e y et a l .,
1972). N e c r o p s y r e v e a l e d ei g h t i m m a t u r e a r t e r i a l w o r m s in
the r i g h t c o m m o n c a r o t i d a r t e r y a n d n u m e r o u s "fifth st a g e
nematodes
in
the
arteries
of
the o p t i c n e r v e
s h e a t h and
sclera" ( W o r l e y et al., 1972).
Three additional moose infected with E. schneideri were
collected from other areas in southwestern Montana. A mature
cow
with
28 a r t e r i a l
worms
was
found
in P a r k C o u n t y in
November of 1971, and a Cow moose from the Bridger mountains
had eleven adult worms. A young female moose found with the
5
previous
c o w wa s i n f e c t e d w i t h o ne a d u l t w o r m
( W o r l e y et
a l ., 1972).
Later
su r v e y s
in w i l d
additional moose-and,
with E.
schneideri
ruminants
from
for the first time,
(Worley,
1975).
The
Montana
found
mule deer infected
data
indicated that
m o o s e h a v e a "lack of r e s i s t a n c e " to the a r t e r i a l n e m a t o d e
while mule deer showed lower w o r m burdens and presumably are
asymptomatic
These
surveys
(Wo rl ey,
1975; W o r l e y
indicate
that
et a l . , u n p u b l i s h e d ) .
t he a r t e r i a l
worm
exists
in
isolated areas in the foothills and mountaineous areas above
1950 meters in southwestern Montana
To date,
Montana
(Worley,
1975).
e Iaeophorosis in elk has not been reported
(Worley,
1975;
Worley
in
et al.,unpublished). Efforts
to s u r v e y the p o t e n t i a l i n t e r m e d i a t e h o s t s a nd v e c t o r s of
the
arterial
worm
showed
that
a number
of
tabanids
are
s y m p a t r i c w i t h w i l d an d d o m e s t i c r u m i n a n t p o p u l a t i o n s in
southwestern Montana
Although
(Murray,
tabanid
v e c t o r s of E l a e o p h o r a
southwestern
United
Clark,
Davies,
1972;
1972;
species
have
schneideri
St a t e s
1979;
Worley,
be e n
1975).
incriminated
as
in the s o u t h e a s t e r n a nd
(Hibler
et
C o u v i llion
al.,
et
1969,
al.,
1971;
1984)
the
vectors of the arterial w o r m in Montana are unknown.
B e c a u s e 82.4% of the m u l e d e e r fo u n d i n f e c t e d w i t h E.
s c h n e i d e r i w e r e f r o m the B r i d g e r R a n g e n o r t h of B o z e m a n ,
the study was concentrated on the west and east side of the
Bridger Range.
The purposes, of this study were I) to collect
6
an d i d e n t i f y s p e c i e s of th e f a m i l y T a b a n i d a e o c c u r r i n g in
southwestern Montana;
determine which species
2) to d i s s e c t t a b a n i d s c o l l e c t e d to
serve as intermediate host for the
imm ature forms of E. sch ne id er i;
and 3) to collect data on
the p a r i t y ( o v i p o s i t i o n histor y) of t he f e m a l e t a b a n i d s at
intervals
seasonal
during
the
horse
fly
season
to
analyze- the
aspects of Elaeophora transmission and if possible
clarify the restricted host range of the parasite.
I
MATERIALS AND METHODS
The Bridger Range is located in the northeastern corner
of G a l l a t i n
c o u n t y n o r t h of B o z e m a n ,
Montana
(Figure I).
The r a n g e lies in a n o r t h w e s t - s o u t h e a s t e r l y d i r e c t i o n and
extends
from approximately
8-9 k m northeast of Bozeman,
40
k m n o r t h w e s t to B l a c k t a i I M o u n t a i n (Figure I). Th e ra n g e
i
covers approximately 345.6 k m . Study areas
were located on
the
east
(Figure
and
I),
west
40
sl o p e s
km
north
of
of
the
northern
Bozeman,
Bridger
range
a nd
comprised
was
located
12.8
k m ^ of the total Bridger range area.
The st u d y si te on the
south
of
Flathead
Pas s
west
sl o p e
3.2 k m
in the N o r t h C o t t o n w o o d d r a i n a g e
n o r t h w e s t of the A r m s t r o n g ranch.
T r a p sit es
1985
from the ranch boundary
were
located 7.2 km northeast
along North Cottonwood Creek
In
19 8 4,
tr a p
in 1984 a nd
(Figure 2).
locations
on t h e
east
sl o p e
of
the
Bridger range included the mi ddle fork of Brackett Creek and
the Fairy Lake area . Additional trap sites
were located on
the Ca r r o l C r e e k d r a i n a g e a nd the M i d d l e f o r k of B r a c k e t t
Creek
during
the 1985 collecting season. Trapping was also
done in the Gallatin mountains,
the m a i n
3) .
approximately 25 k m south of
s t u d y ar e a in the v i c i n i t y
of R a t L a k e
(Figure
8
GALLATY n ~ C o .
BO Z EM AN
LIVINGSTON
8 km
Study
- - -
Mountain front
Figure I. Study area in the Bridger R a n g e , summers 1984 and
1985. A, Armstrong Ranch; B , Baldy Mt; R, Carrol
Creek; D, Fairy Creek; S, Brackett Creek, F ,
Frazier Creek; N , North Cottonwood Creek; P, Flathead Pass road; T, Blacktail Mt; W, Sacajawea Peak.
9
Armstrong Ranch
V
/
J1 I
SACAJ AWE Ay fc
PEAK
^
2929 m
O
LAKE
Fly trap sites, summer 1984
\
IR O S S
* PEAK
Fly trap sites, summer 1985
i
- - -
Fly trap sites, summers 1984 and 1985
Mountain front
Figure 2. Location of Manitoba fly traps in the S, Brackett
Creek; R, Carrol Creek; Fairy Lake area, and North
Cottonwood Creek drainages in the Bridger Ra n g e ,
summers 1984 and 1985.
10
Squaw Creek
±J>Ranger S t a t i o n
GARNET
-Rat
Lake
.8 km
|\^\^)
Study area
Figure 3. Collecting area in the Rat Lake campground in the
Gallatin Range, summer 1985.
11
Tabanids
were
collected
with
modified
Manitoba
fly
tr a p s ( T h o m p s o n 1969; C a t t s 19 7 0, A d k i n s et a I .,I 9 7 2). The
tr ap s
were
Han over,
made
of
fiberglass
screening
(CCS
PA). F l a t sh e e t s of t he m a t e r i a l
were
Hanover,
cut
in t o
fo ur i d e n t i c a l t r a p e z o i d s w i t h t he f o l l o w i n g d i m e n s i o n s :
base, 175 cm, top edge, 12.5 cm, a nd sides of 187.5 cm.
side s of th e i n d i v i d u a l
T he
t r a p e z o i d s w e r e s e w n t o g e t h e r to
f o r m a th r e e d i m e n s i o n a l
structure
(F i g u r e
4) th a t h a d a
175 c m 2 bo tto m opening and a 12.5 c m 2 top opening.
Canvas
webbing
trapezoid seams
was
(Figure
Th e t r a p collar,
to
to
(Figure 4) and
for reinforcement
served
sewn
hold
an
the
lower
lo c a t e d in the a p e x of the t r a p e z o i d
inverted
acetate
vinyl
(Figures
beach
painted wi th black glossy vinyl
from
the
5,A).
body and the adjustable pole
inflatable
of
to the apex of the trapezoid
funnel,
a t t a c h m e n t a r e a for the t o p c a n i s t e r ,
An
third
provide
an
the f i b e r g l a s s tr a p
5,
ball
A,B,C).
(60
cm,
spray paint,
di a m e t e r ) ,
was
suspended
the po l e w i t h a n y l o n r o p e , so t h a t 2/3 of the ball
was below the edge of the canopy when viewed from a distance
(Figure.
the
4). T h e b l a c k co l o r s e r v e d to c o n c e n t r a t e h e a t on
surface
(Thorsteinson,
the
of
the
1958).
ball
and
thus
attract
The edge of the canopy was
tabanids
60 cm from
ground.
Use of f i b e r g l a s s s c r e e n i n g to b u i l d t he t r a p c a n o p y
and
insect
holding
container
eliminated
weight
and
12
Figure 4. Modified Manitoba fly trap used to collect horse
and deer flies, summers 1984 and 1985.
13
Clamp
Figure 5. Detailed view of the (A) collar, (B) collecting
funnel, (C) aluminum tube, wood dowel, and attach­
ment to the trap collar. Fm, fiberglass mesh; Acc,
inverted acetate funnel; Sgo, ShooGoo sealer; Cw,
canvas webbing; P , collar with center support; Wd,
wood dowel; Al, aluminum tube; Wb, wing bolt and
nut.
14
c o m p a c t a b i l i t y p r o b l e m s of t h e c o n v e n t i o n a l M a n i t o b a fly
trap.
This
modification
also eliminated
the
need
to
invert
the c o l l e c t i n g c a n i s t e r (to f o r c e s w a r m i n g of t h e t r a p p e d
flies at the apex of the trapezoid) as re co mm e n d e d by Davies
(1979) to increase
the
inside
fly survival.
surface
of
activity after capture,
the
Tabanids readily rested on
can is te rs .
This
reduced
fl y
and m i n i m i z e d da mage to anatomical
characters important in identification.
Fly Survival
To
ensure
fly
survival
transportation to Bozeman,
during
collection
a styrofoam cooler 30 cm x 20 cm
x 40 c m w a s m o d i f i e d to fit in t o a backpack.
frozen
bag s
were
attached
to
the
internal
T h r e e B l u e Ice
walls
cooler at the beginning of each collecting period.
were frozen
in
-20.5 C b e f o r e
a
and
of
the
Ice bags
horizontal position for several days at
use,
to e n s u r e
flatness
of
the
ice bags,
thus reduce space used in the cooler.
Collected
bags
tagged
flie s
with
were
the date,
placed
ti me ,
in
pint
size
temperature,
Ziplock
relative
h u m i d i t y (RH)., t r a p site a n d t r a p n u m b e r a n d p l a c e d in the
cooler.
This procedure ma xi mi ze d use of space in the cooler
and allowed 10-15 bags to be transported with m i n i m a l damage
to the flies. A i r w a s r e m o v e d f r o m bags p r i o r to p l a c i n g
them in the cooler.
15
The
fo r
cooler
periods
temperatures
versus
maintained
of
12
and
direct
to
36
temperature
hours,
betw ee n
depending
on
I.1-4.4 C
external
location of the pack during the day (shade
sunlight).
Trapping
T r a p p i n g w a s do n e f r o m J u l y 20 to A u g u s t 30
in 1984 and
f r o m J u n e 19 to A u g u s t 10 in 1985. In the N o r t h C o t t o n w o o d
Canyon,
traps were placed at different altitudes during the
1984 season. Trap A was located at an elevation of 1800 m on
a southwest slope,
1.9 km southwest of the canyon entrance.
T r a p B w a s at 1950 m , 1.9 k m
n o r t h e a s t f r o m t r a p A on a
r o c k y n o r t h f a c i n g slope. T r a p C a n d D w e r e l o c a t e d 7.3 k m
east
of
the
canyon
entrance
respectively (Figure 2), on
ho r s e t a i l ,
sedges, g r a s s e s
the c o l l e c t i n g area,
tr ap s
at
2 31 0
m
and
2 34 0
m
a flat wet m e a d o w , covered with
a nd f orbs. On the ea s t side of
in
1984
were
located
in
the
Fairy Lake area (G) at 2040 m and in the Brackett Creek area
(H ,I ) at 1980 m,
In 1985,
3.2 km
southeast of
Ross.
Peak (Figure
trap s on the w e s t si d e of th e B r i d g e r s w e r e
concentrated in the east end of the canyon.
D
were
located
(Figure 2).
2).
between
2.220
and
2340
Traps A,B,C,
m- a l t i t u d e
and
zone
D u r i n g the 1985 s e a s o n the ea s t side ha d t w o
tr ap s
(E ,F ) in
the
Ca rr o l
Creek
drainage
and
two
(H,I,)
in the B r a c k e t t C r e e k site s o u t h of R o s s Peak.
latter traps were removed due to lack of fly activity.
traps
The
16
Traps
were
checked
the east and w e s t
season.
In 1984,
west side of
for
flies
every
2-3
side of th e s t u d y area d u r i n g
days
the
on
1985
collection of flies was concentrated on the
the area because tabanid activity was
m in im a I
on th e e a s t aide. D u r i n g the c o l l e c t i n g day, e a c h t r a p wa s
checked every 3-4 hours during both collecting seasons.
,
Tabanid
Dissection
T a b a n i d s w e r e t r a n s p o r t e d to t he V e t e r i n a r y R e s e a r c h
L ab a n d s t o r e d at 4 C for 3-4 da y s b e f o r e d i s s e ct io n. E a c h
fly
was
identified
protocol
for
immobilized
prosternum
ventral
to
species
prior
examination
was
by
through
cutting
(Figure
6)
with
as
to
di s s e c t i o n .
follows:
the
tabanids
surface
microscissors
to
Thewere
of
the
sever
the
nerve chord.
The pleural mem bra ne between the abdominal tergites and
s t e r n i t e s wa s cu t l o n g i t u d i n a l l y w i t h the m i c r o s c i s s o r s ,
s t a r t i n g at the t e r m i n a l a b d o m i n a l s e g m e n t s a nd e n d i n g at
the
anterior
a b d o m e n - m e tapleuron
was
done on both
margin
(Figure
6).
This
sides of the abdomen and allowed complete
separation of the dorsal and ventral
segments.
The abdominal halves were placed in 0.86% physiological
sa l i n e solution. The g a s t r o i n t e s t i n a l tract, ovaries, a nd
fat b o d i e s w e r e r e m o v e d a n d p l a c e d in 0.86% p h y s i o l o g i c a l
saline for observation under a dissecting microscope at
an d I 0 OX.
50X
17
Figure 6.
The
Cr o s s s e c t i o n (A) and lateral v i e w (B) of a
horse fly showing the
location of the pleura I
m e m b r a n e . T, a b d o m i n a l terga; S , a b d o m i n a l
sterna; P, pleural
membrane; p i g , metapleuron;
stn^,
prosternum;
F, fat c e l l s lining the
interior of the abdominal sclerites.
thorax
was
opened
at
the
midlateral
line
bilaterally and separated to expose the thoracic muscles and
gastrointestinal
bo d y
tract
r e g i o n s , the
minutes
components.
he ad
was
While
dissecting
s e v e r e d and
in p h y s i o l o g i c a l saline.
other
left for five
T he c e p h a l i c e n d of the
food can al w a s o b s e r v e d for e m e r g i n g
larval
f o r m s , th e n
teased apart and viewed under a dissecting microscope.
Ovaries
were
teased
dissecting
microscope
individual
ovarioles
present
recorded.
at
were
The
apart
I 00X.
while
T he
observed
number
of
viewed
follicular
and
any
under
tubes
a
of
dilatations
dilatations
in
the
18
follicular
tubes
(oviposition
Bertram,
is
his tor y)
used
as
an
of f e m a l e
indicator
flies
of
parity
(Detinova,
1962,
1962). P a r i t y is the c o m p l e t i o n of a g o n o t r o p h i c
cycle,
where a gonotrophic cycle consists
steps;
search for a host,
of a n u m b e r of
feeding on its blood,
digestion of
the blood m e a l , and oocyte maturation followed by ovipositon
(Thomas,
1972);
An
absence
lack
of
prior
indicates
(uniparity)
dilatations
represents
(biparity),
of
dilatations
oviposition,
one
prior
(nulliparity)
one
dilatation
oviposition,
two prior ov ip ositions, etc
1972; Magnarelli and Pechuman,
two
(Thomas,
1975).
Parity of individual females together with the time of
emergence is used to determine
the absence
of a blood meal,
d e p e n d e n t on a b l o o d m e a l
T h o m a s , 1972).
When
autogeny,
egg maturation in
or anautogeny,
(Cameron,
nulliparity
is
egg maturation
1926; S p i e l m a n ,
rare
or
1971;
absent,
that
population is autogenous. A population with large numbers of
nulliparous individuals is anautogenous
Magnarelli and Anderson,
(Thomas,
1.969,
1972;
1981).
Observations of the fat body present in the abdomen of
the t a b a n i d s
goal,
wa s done.
an a r b r i t a r y
portion
of
A l t h o u g h this w a s n o t an o r i g i n a l
sc al e
the a b d o m i n a l
moderate portion;
(+++,
space;
fat bo d y o c c u p i e d a large
++,
fat b o d y
occupied
+, fat body occupied a small portion)
a
was
u s e d to m e a s u r e the a m o u n t of a b d o m i n a l sp a c e t h e fat b o d y
19
occupi ed .
Pa t
body
da t a
were
used
with
parity
data
to
determine autogeny or anautogeny of tabanids dissected.
T a x o n o m i c i d e n t i f i c a t i o n of h o r s e a n d d e e r flies w a s
based
on
keys
by
(1979),
Teskey
larval
nematodes
descriptions
1 9 8 5 ),
Phillip.
(1936),
found
by H i b l e r
Poinar
descriptions
(1935).
and
Gittins
(1983) an d T u r n e r (1985). I d e n t i f i c a t i o n of
et
in
by
the
tabanids
a nd M e t z g e r
a I.
Identification of anatomical
on
Nowiersky
Borror
( 1 9 7 6 ),
was
(1974),
and
based
Poinar
Sonin
on
(1975,-
(1 98 5 ).
features of tabanids was based
et
al.
(1976),
and
Snodgrass '
20
RESULTS
A to ta l
thirteen
species
of
1122
fli es
representing
t h r e e g e n e r a a nd
s p e c i e s w a s c o l l e c t e d d u r i n g 1984 a n d 1985. T he
and
the
percent
composition
for e a c h
s e a s o n are
g i v e n in T a b l e I. Of th e 1122 f l i e s c o l l e c t e d ,
9 9 2 (88.4%)
w e r e d i s s e c t e d an d 130 (11.6%) w e r e p i n n e d for i d e n t i f i c a ­
tion. Of t h e 992 fl ie s d i s s e c t e d ,
784 w e r e d i s s e c t e d a f t e r
immobil iza tio n as discussed previously and the remaining 208
flies were dissected after being frozen for nine months.
F l i e s c o l l e c t e d on the e a s t si d e of the B r i d g e r R a n g e
totaled 356 for all species compared with 447 from the west
side, and 319 from the Gallatin Range south of Bozeman,
Specimens
Range
included
c o l l e c t e d on t he e a s t
Atylotus
insuetus,
side
of t h e
Chrysops
MT.
Bridger
exitans,
C.
f u r c a t u s , H y b o m itr a o p a c a , H. o s b u r n i , H. r u p e s t r i s , a n d H
tetrica during both
same
period
on
the
seasons.
west
Tabanids collected
side
of
the
range
i n s u e t u s , C . f u l v a s t e r , H . c a p t o n i s , H.
during the
included
m e l a n o r h i n a , H.
IasiophthaIma , H. os bu rni , H. rupes tr is , and H.
Additional
trapping and
collecting
A.
with
an
tetrica.
insect net
(two day period) at Rat Lake in the Gallatin Mountains south
of B o z e m a n y i e l d e d the f o l l o w i n g s p e c i e s : A. i n s u e t u s , C.
a t e r , C. f u r c a t u s , H. o s b u r n i , H. r u p e s t r i s , a n d H. tetrica.
Table
I.
Horse fly and deer fly species collected in southwestern Montana,
198 4 and .198 5.
I 9 8 4
N o . of
Flies
Species
Species
%
Atylotus insuetus Osten Sacken
4
I .5
Chrysops ater Macpuart
-
-
Chrysops exitans Walker
-
Chrysops fulvaster Osten Sacken
I 9 8 5
N o . of
Flies
summers
Tot a I s
Species
%
N o . of
Fli es
Species
%
12
1.4
16
1.4
I
0.1
I
0.1
-
2
0.2
2
0.1
-
-
4
0.5
4
0.4
Chrysops furcatus Walker
-
-
12
I .4
12
1.1
Chrysops noctifer Osten Sacken
3
I .I
8
0.9
11
1.0
Hybomitra captonis
2
0.8
4
0.5
6
0.5
-
-
I
0.1
I
o.l
•I
0.4
-
-
I
0.1
I
0.4
I
0.1
216
81.2
348
40.7
564
50.3
Hybomitra rupe str is .(McDunnoueh)
23
8.6
.196
22.9
219
19.5
Hybomitra ■tetrica' (Marten)
16
6.0
269
32.3
284
25.3
266
100.0
856
100.0
1122
100.0
(Marten)
Hybomitra lasiophthalma
(Mareuart)
Hybomitra melanorhina (Bieot)
Hybomitra opaca
(Coeuillett)
Hybomitra osburni _(H i n e )
Totals
W
H
22
Seasonal Distribution of Tabanids
S e a s o n a l d i s t r i b u t i o n of th r e e of the t a b a n i d sp e c i e s
c o l l e c t e d is g i v e n in F i g u r e s
7 and 8. H y b o m i tra o s b u r n i
p e a k e d in n u m b e r s th e la t t e r p a r t of Ju l y in 1985. Th e p e a k
in 1984 w a s no t as lar ge b ut a l s o o c c u r r e d in late J u l y and
early August
(Figure 8).
Hybomitra
rupestris
and H.
tetrica
w e r e p r e s e n t in e a r l y s u m m e r
(late June to e a r l y July) in
1985. T he last
were rarely collected after
two
sp e c i e s
mid-July during both seasons.
Fly Dissection and Recovery of Elaeophora schneideri Larvae
Tw o Tabanid
positive
for
species, H. rupestris; and H. tetrica were
first
(L1 ) (Figures
stage Elaeophora schneideri larvae
9,
10)
and
second
(Figure 11).
(L2 )
One species,
H. o s b u r n i , w a s p o s i t i v e for L 1 larvae. I n f e c t e d t a b a n i d s
were found only in the study area west of the Bridger Range
front.
H y b o m itra o s b u r n i
an d H. r u p e s t r i s
ho s t r e c o r d s for th is f i l a r i i d (Table 2).
represent new
A s u b s p e c i e s of
H. t e t r i c a , H. t e t r i c a r u b r i lata is an a c t i v e v e c t o r of the
a r t e r i a l w o r m in s o u t h w e s t e r n U n i t e d S t a t e s
Hibleretal.-,
Eight
of
(Clark,
1972;
1971b).
99 2
flies
(0.8%)
were
positive
for
E.
s c h n e i d e r i l a r v a e in 198 4 a n d 19 8 5 (Table 2). The p e r c e n t
i n f e c t i o n w a s 0.5% in 1 9 84 , a n d 0.9% in 1985 (Table 2).
total
number
of
larvae
recovered
was
54
(Table
The
3).
Measu rem ent s of the L 1 and L 2 stages are given in Table 4.
r— ,
# # #
Hybomitra osburni
<}— <— <
Hybomitra rupestris
D-o-a
Hybomitra tetrica
o 140
JULY
AU GUST
Figure 7. Seasonal distribution of three horse fly species
collected in the Bridger R a n g e , summer 1985.
24
»-*-# Hybomitra osburni
4—4—4 Hybomitra rupestris
Number of Tabanids Collected
□— d - d Hybomitra tetrica
28
JULY
AUGUST
Figure 8. Seasonal distribution of three horse fly species
collected in the Bridger R a n g e , summer 1984.
25
Figure 9. Early first stage larva of Elaeophora schneideri
from a female Hybomitra o s b u r n i , summer 1984. E c ,
excretory cell; I n t , intestine; Re, rectal cell.
Magnification 2 0 0 X .
26
Figure 10. First stage larva of Elaeophora schneideri from
a female Hybomitra rupes tr is , summer 1985.
Magnification 125X.
27
Figure 11. Second stage larvae of Elaeophora schneideri from
a female Hybomitra t e t r i c a , summer 1985. A p , anal
plug; G e s , glandular esophagus; I n t , intestine.
Magnification 6 0 X .
Table 2. Horse and deer fly species examined for Elaeophora schneideri
1984 and 1985.
1984
Species
No.
Dissected
Aty IotusI i n s u e t u s
I
larvae, summers
1985
%
Infected
0.0
No. .
Dissected
I0
Totals
%
Infected
No.
Dissected
%
Infected
0.0
11
0.0
Chrysops exitans
-
I
0.0
I
0.0
Chrysops furcatus
-
7
0.0
7
0.0
Chrysops noctifer
-
5
0.0
5
0.0
Hybomitra captonis
-
2
0.0
2
0.0
334
0.0
537
0.2
Hybomitra osburni
203
0.5
Hybomitra rupestris
3
-
' 169
1.8
172
1.7
Hybomitra tetrica
2
-
255
1.6
257
1 .6
783
0.9
992
0.8
Totals
2 09
0.5
%
29
Table 3. H o r s e
fly species
infected with
sch neideri, summ er s 1984 and 1985.
Species
Loc.
Elaeophora
Flies
Infected
No. of Larvae
.Recovered
Hybomitra
osburni
NC
I
3
Hybomitra
rupestris
NC
3
10
Hybomitr a-. ^
tetrica
NC
4'
41
8
54
Totals
NC-North Cottonwood C a n y o n , Bridger M t s . Gallatin Co. MT.
Table 4. Mea surements of Elaeophora schneideri larvae from
horse flies in southwestern
Montana, summers 1984
and i 1985. AlI measurements in mi crometers (urn).
Larval
Stage
n
Length
x (r a n g e )
Width
x(range)
L1
32
975(357-1190)
40.2(31.6-49.7)
L2
22
1767(1454-2825)
39.3(33.3-49.7)
Recovery of Mermithidae
Specimens
recovered
from
of
an
the
unidentified
fat bodies,
me rmithid
tracheoles,
nematode
and
were
in te r n a l
o r g a n s u r f a c e of s o m e t a b a n i d s , i n c l u d i n g a s p e c i m e n f r o m
the
lumen
of
the
uterus.
Twelve
percent
dissected were carrying this nematode during
of
the
1984 and
flies
1985.
The infection percent for each collecting period is given in
T a b l e 5.
Table 5. Horse and deer
1985 .
fly species
examined
for m e rm it hi d n em a t o d e s , summers
1984'
Species
No.
Dissected
1985
%
Infected
Atylotus insuetus
I
O .O
Chrysops exitans
-
Chrysops furcatus
No.
Dissected
198 4 and
Totals
%
Infected
No.
Dissected
%
Infected
10
0.0
11
0.0
-
I
0.0
I
0.0
-
-
7
0.0
7
0.0
Chrysops noctifer
-
-
5
0.0
5
0.0
Hybomitra captonis
-
-
2
0.0
2
0.0
Hybomitra osburni
203
8.8
334
18.8
537
15.0
Hybomitra rupestris
3
0.0
169
14.7
172
14.5
Hybomitra tetrica
2
0.0
255
5.4
257
5.4
209
8.6
783
13.0
992
12.0
Totals
w
O
31
'
The nematode
tab an id s,
and
organism
was
was
found in
16.7%
(2/12)
always
12.1%
of
found
(120/992) of thefemale
t he
dead,
males
examined.
melanized
and
The
coiled
(Figures 12, 13, 14). Th e m e l a n i z a t i o n d i f f e r e d in p i g m e n t
concentration from specimen to specimen. The significance of
melanization will be discussed later.
Parity Data
P a r i t y dat a
1984 only,
were
and for
c o l l e c t e d for A t y l o t u s
insuetus
in
H. os b ur ni , H. rupestris, and H. tetrica
in 1984 an d 1985. T a b l e 6 s h o w s th a t 95.6 % (194/203) of H.
osburni,
dissected
were
uniparous,
3.4%
n u l l i p a r o u s , and 1.0% (2/203) w e r e b i p a r o u s
i n d i v i d u a l s of A. in s u e t u s
(7 /2 03 ) w e r e
in 1984.
(1/1), H. r u p e s t r i s
All
(3/3) a nd H
tetrica (2/2) examined in 1984 were nulliparous.
In 19 8 5 (Table 7),
u n i pa ro u s,
27.2%
and
(91/334)
rupestris
had
13.2%
5 9.6% (199/334) of Hjl o s b u r n i w e r e
(44/334)
flie s
co u l d
39.6%
(67/169)
(53/169) nulliparous,
unk no wn .
H y b o m it ra
fe m a l e s ,
28.6%
and
not
be
T he p a r i t y
determined.
specimens
had
20.4%
nulliparous,
(52/255)
and
of
H y b o m itra
u n i p a r o u s , 31.4%
in 29.,0% (49/169) the
tetrica
(73/255)
nulliparous.
51.0%
parity was
uniparous
(130/255)
were- unknown.
Data relevant to
fat body development
s h o w e d that the m a j o r i t y of H. o s b u r n i
63.1% in 1985)
(Tables 6 and 7)
(71.1% in 1 984 , and
were uniparous and had a well
developed fat
32
Figure
12. M e r m i t h i d n e m a t o d e f r o m a f e m a l e H y b o m i t r a
o s b u r n i , s u m m e r 1984 . M a g n i f i c a t i o n 175X.
33
Fi g u r e 13. M e r m i t h i d nematode from a male H y b o m i t r a o s b u r n i ,
summer 1985. M a g n i f i c a t i o n 145X.
34
Fig u r e 14. M e r m i t h i d n e m atode from a female H y b o m i t r a
tetrica, summer 1985. M a g n i f i c a t i o n 145X.
35
Table 6. P a r i t y of t h r e e
s u m m e r of 1984.
horse
Species
fly
species
di s s e c t e d ,
P a r i t y (n)
Fat
+++
Atylotus insuetus
Ulb
I
Hybomitra osburni
U( 194)
N (7 )
B C2 )
Hybomitra rupestris
Hybomitra tetrica
s
b
Body d
++
+
O
O
138
6
2
50
.I
O
6
O
d
N( 3)
2
I
O
N( 2)
2
O
O
Fa t b o d y / c e l l s d e v e l o p m e n t , + + + = w e l l d e v e l o p e d ,
medium development, += poorly developed,
N= nulliparous, U= U n i p a r o u s , B= Biparous
body in the abdomen.
Uniparous and nulliparous
++=
individuals
of H . r u p e s t r i s an d H . t e t r i c a h a d a hi g h p e r c e n t of w e l l
developed fat bodies.
A
comparison
of
the
number
of
flies
found
to
be
u n i p a r o u s an d n u l l i p a r o u s w i t h the date w h e n c o l l e c t e d is
given
in F i g u r e
15.
This
was
done
for e a c h of
the t h r e e
c o m m o n species. H y b o m itra o s b u r n i s h o w e d a low n u m b e r of
nulliparous
individuals,
present
large
in
w h i l e u n i p a r o u s individuals were
numbers
H y b o m i t r a r u p e s t r is
during
initially
the
showed
summer
a larger
of
1985.
number
of
n u l l i p a r o u s i n d i v i d u a l s b ut u n i p a r i t y a p p e a r s to i n c r e a s e
after July 2nd and probably stays level until July 24th. The
low n u m b e r of u n i p a r o u s m e m b e r s d u r i n g J u l y 14 to
reflect
lo w n u m b e r s
16 m a y
c o l l e c t e d d u r i n g t h a t p e r i o d (Figure
36
7).
Nulliparity
and
uniparity
throughout the s u m m e r for H.
Table 7. P a r i t y
summer
of th r e e
of 1985.
Species
Hybomitra osburni
Hybomitra rupestris
Hybomitra tetrica
a
b
c
were
similar
in
number
tetrica.
horse
f ly s p e c i e s
P a r i t y (n)
U ( 190)b
U (9 )
N (3 7 )
Ni 7)
-(91)
dissected,
Fat Bodyd
+++
++
+
120
25
-
59
12
-
' U (5 9 )
U (8 )
N (3 3 )
N (2 O )
•-(49)
47
19
-
7
I
-
5
13
-
U (3 5 )
U (17 )
N (4 1 )
N (32 )
-(130)
35
31
-
0
0
-
0
10
-
Fat b o d y / c e l l s d e v e l o p m e n t , +++= we l l d e v e l o p e d ,
++= m e d i u m development, += poorly developed.
N = n u l I i p a r o u s , U= U n i p a r o u s , B= B i p a r o u s
No data available.
11
-c
0
-
Number
of
Tabanids
37
02
JULY
06
AUGUST
Figure 15. Number of nulliparous and uniparous individuals
of three horse fly species trapped in the summer
of 1985.
38
DISCUSSION
Species Composition
of Tabanidae
Differences in tabanid species
of
the
Bridger
reflect
the
behavioral
efficiency.
Range
habitat
aspects
of
an d
in the
collected on both sides
Gallatin Range probably
selection
during
individual
species
trap
placement,
present,
and trap
I suspect that all species collected are present
throughout the Bridger and Gallatin Mountains.
Comparative studies of fly traps show that canopy traps
are
efficient
for horse
of deer flies.(Roberts,
reported
that
flies
while attracting few
1976; Thomas,
1970).
the Manitoba trap collects
species
Thompson
more
(1969)
specimens of
deer flies than any other method.
Results of this study are
similar to collections by Thomas
(1970).
The Manitoba traps
collected more species of horse flies than'deer flies.
M a l e t a b a n i d s a r e n o t o f t e n c a u g h t u s i n g M a n i t o b a fly
traps
a
(Thomas,
fi x e d
fe m a l e s ,
area
1970; Roberts,
or
lie
then engage
on
1976). The male flies hover in
vegetation
in a c t i v e
waiting
pursuit
for
(L e p r i n c e
1983). Th is b e h a v i o r m a y e x p l a i n h o w the m a l e s ,
exclusively nectar feeders
(Kniepert,
1980;
passing
et al.,
w h i c h are
Leprince et al.,
1983) were captured in the Manitoba traps.
The s e a s o n a l
for
three
of
the
o c c u r r e n c e of
thirteen
tabanids
species
was determined
collected
(H y b o m i t r a
39
osb urn i,
H.
r u p e s t r i s , an d
H.
t e t r i c a ).
In
the
Bridger
Range, H. osburni was abundant throughout the s u m m e r in 1984
and 1985. Numbers of this species decreased from July 14 to
Ju ly 16, 1985, th e n i n c r e a s e d a nd d r o p p e d a g a i n on Ju l y 16,
1985.
,I b e l i e v e
th e d e c r e a s e
in n u m b e r s
is the r e s u l t of
w i n d y c o n d i t i o n s , c l o u d i n e s s an d t e m p e r a t u r e dr o p s d u r i n g
the
collecting periods
mentioned,
rather than t wo separate
e m e r g e n c e p e a k s . An i n c r e a s e in n u m b e r s
late J u l y to e a r l y A u g u s t
(F igures
was noticed
from
7 a n d 8). In contrast,
this s p e c i e s pe a k s in n u m b e r s in e a r l y J u l y in A l b e r t a b u t
remains present fr om mid-June to mid-August
(Thomas, 1970).
Numbers of Hybomitra rupestris and H. tetrica peaked in
early July
from
a
in 1985 (Figure 7) and a p p e a r e d to be d r o p p i n g
similar
peak
in
1984
(Figure
8).
Thomas
(19 7 0)
r e p o r t e d th at H. r u p e s t r i s e m e r g e d in late J u l y w i t h p e a k
numbers in early August.
differences
between
This m a y be attributed to latitude
Alberta
an d
southwestern
Mo nt an a.
H o w e v e r , e m e r g e n c e of H. t e t r i c a w a s s i m i l a r to e m e r g e n c e
patterns of H.
tetrica hirtula in Alberta with peak numbers
present during the first ten days of July.
Horseflies and Elaeophora schneideri
Clark
species
(1972)
found
six
in northern New Mexico
of E. s c h n e i d e r i . H y b o m it r a
horse
fly
and
infected with
laticornis made
on e
deer
larval
up
90%
fly
stages
ofa ll
infected flies. Simil ar studies in'Vermejp park. N e w Mexico,
40
showed 98% of the vectors
aatos
(Davies,
Three
st a g e s
(Table
3).
individual
to be Hybomitra
1979).
tabanid
larval
of E. schneideri
sp e c i e s
of the
One
arterial
species,
vectors
were
H.
fo u n d
worm
tetrica
collected
(Table
infected
in th e
made
with
present
up
3). T h e
50%
the
study
of
the
L3
infective
stag e of E. s c h n e i d e r i w a s no t r e c o v e r e d f r o m
dissected
and L 2 stages were found (Table 3).
flies whereas
H y b o m itra o s b u r n i w a s the m o s t c o m m o n fly c o l l ec te d,
but
its
importance
minimal.
Hybomita
have
a greater
worm
in
as
a vector
rupestris
ro le
and
of
E.
schneideri
Hybomitra
in the t r a n s m i s s i o n
southwestern
Mo nt an a.
The
tetrica
of
l at te r
may
be
probably
th e a r t e r i a l
species
had
a
higher infection percentage than H. osburni.
Wh y Hybomitra rupestris and H. tetrica have the highest
prevalence
of
infection
is
not
known.
The
fact
that-
Hybomitra species act as vectors in southwestern Montana is
not surprising. Hybomi tra species are the most c o m m o n vector
of E. schneideri in the
and Adcock,
southwestern
United
States
(Hibler
1971).
M e m b e r s of the ge nu s T a b a n u s have b e e n i m p l i c a t e d as
vectors
(Clark,
infection
is
1972;
I ow.
Davies,
Specimens
collected during this study.
1979) but the p r e v a l e n c e of
of
this
species
were
The absence of Tabanus
not
species
m a y i n d i c a t e the lack of this g e n u s in t he ar e a s sa mp l e d ,
si nc e T a b a n u s s p e c i e s ar e r e a d i l y c o l l e c t e d w i t h M a n i t o b a
41
tr ap s
(T ho rs te ins on ,
1958;
Thompson,
1969;
Thomas,
1970;
D a v i P s , 1979; P e c h u m a n et a l ., 198 3 ). C h a p m a n (1954) s h o w e d
that
Tabanus
observed
at
sequax
was
Squaw
peak,
the
only
member
Missoula
of
Co.,
this
Montana
ge n u s
at
an
elevation of 2423 m.
The la rva l st ag e of E. s c h n e i d e r i r e c o v e r e d f r o m the
th re e t a b a n i d s p e c i e s m a y d e p e n d on the
vector
species
involved.
Olkowski
l o n g e v i t y of the
(1966)
s t a t e d th a t the
mean survival after emergence of Tabanus nigrovittatus
12.3 days. T h o m p s o n an d K r a u t e r
nigrovittatus
days,
of
and
T.
(1980)
_1. h i n e Ilus
only
was
s h o w e d t h a t for T.
50%
survived
six
18% for 14 days, a n d 5-7% f o r 21 days. F i f t y p e r c e n t
Tabanus acutus survived for 9 days,
15-20%
for
14 d a y s ,
a n d 5-6% fo r 21 days.
If t h e s e l o n g e v i t y d a t a a r e a fair r e p r e s e n t a t i o n of
Pv,
tabanid
populations,
schneideri
to
develop
an d
to
.
two
the
weeks
are
infective
required
Lg
for
sta ge
E.
after
i ni ti al i n g e s t i o n b y a fly, o n l y 5-6% of a n y g i v e n t a b a n i d
p o p u l a t i o n w o u l d be a v a i l a b l e to a l l o w d e v e l o p m e n t to the
infective stage. These flies would have 4-5 days of survival
after acquiring E.
schneideri
larvae.
Because of these time
l i m i t a t i o n s , suc h a fly p o p u l a t i o n w o u l d be a d e a d end for
the arterial nematode larvae.
Longevity
of
tabanids
appears
to
vary , and
no
comparative work is available for species of North America.
C h v a l a et a I ., (I 9 7 2) r e p o r t e d t h a t a d u l t h o r s e fli es
live
for si x weeks. This d i f f e r s s i g n i f i c a n t l y f r o m the w o r k by
Olskowski
(1966)
and Thompson and Krauter
(1980)
previously
Autogenous species may acquire E Iaeophora
l ar va e at
cited.
the
beginning
second
of
the
gonotrophic
definitive
host
as
gonotrophic
cycle)
the
that
energy
cycle
(actually
requires
source.
blood
The
their
from
latter
a
egg
d e v e l o p m e n t c y c l e m a y b e g i n at a p o i n t w h e n o n l y 6-7 days
are left in the vector's
lifespan.
This c o u l d be th e ca s e
for H. osburni and would allow development of E. schneideri
larvae to the
stage. Anautogenous species,
infected shortly after emergence,
if they became
would have enough time for
the d e v e l o p m e n t of E. s c h n e i d e r i
l ar va e to th e i n f e c t i v e
stage. Th is s c e n a r i o m a y be p r e s e n t in H. r u p e s t r i s a nd H.
tetrica in southwestern Montana.
The
prevalence
of
the
arterial
southwestern Montana was low
New Mexico,
of
H.
in
tabanids
(Hibler et a l . , 197 1). D a v i e s
aa to s
infected
in
(0.8%), compared to Arizona and
w h e r e the a v e r a g e p r e v a l e n c e is 14.5%
1972 ) an d 19.1%
10%
worm
an d
studies
showed a prevalence of 0.3% in Tabanus
in
I.
(Clark,
(1979 ) f o u n d
South
Carolina
hinellus
surveyed
(C o u v i l I ion et al., 19 8 4).
Specimens
of
a
nematode
believed
to
belong
to
the
family Me rmi thi dae were present in the fat bodies and other
internal
organs
of
f lies
during
present
study.
Similar
43
organisms were
identified as dead
w o r m by Davies
(1979).
stages of the arterial
Identification of the m e r m i t h i d species was impossible
due
that
to
melanization,
involves
leucocytes,
a nd
of
Coordinated
cellular-humoral
a number
of
lymphocytes,
precipitation
portion
a
the
or
of
insect
blood
defense
cells
m i c r o ne uc lo cy te s,
components
haemolymph
individual
from
m e ch an is m
(amoebocytes,
thrombocytoids)
the
n o n - c e l lular
( R a t c l i f f e and R o w l e y ,
actions
by these
1979).
systems
results
in the f o r m a t i o n or r e l e a s e of p r e c u r s o r s n e e d e d
for the
f o r m a t i o n of t h e p i g m e n t m e l a n i n (P o i n a r et a I., 1 9 7 9).
s u c c e s s f u l r e s p o n s e by the h u m o r a l
deposition
of
melanin
layer s
system results
around
e n t e r i n g the h a e m o c o e l of an i n s e c t
AlI
mer mithids
melanin
collected
present
were
varied.
a
foreign
and
melanized,
General
Leutenegger,
in the
object
(Poinar et a l ., 197 9).
but the degree of
anatomy
of
invading
nematodes, remain constant through the melanization
(Poinar
A
1971,
Po inar.,
process
personal
c o m m u n i c a t i o n ) . T he n e m a t o d e s w i t h lo w a m o u n t s of m e l a n i n
present
on
the
surface
of
the
cuticle
did
not
fit
d e s c r i p t i o n s of larval s t a g e s of E. s c h n e i d e r i (H i b l e r and
Metzger,
1974).
The mer mithids were probably obtained during the larval
st ag e of the t a b a n i d s an d d i e d as a r e s u l t of m e l a n i z a t i o n
3-5
days
after
infection
(Poinar,
personnal
C o m p a r i s o n of m e l a n i z e d n e m a t o d e s
communication).
collected
from
female
44
horse
fl i e s
an d
specimens
morphologic features
from
male
horse
fl ie s
showed
s i m i l a r to the l a r v a e i d e n t i f i e d as
m e r m i t h i d s in this s t u d y (F igures 13, 14). S i n c e m a l e s are
strictly nectar feeders
1983) and E.
schneideri
(K n i e p e r t , 1980;
L e p r i n c e et a I .,
larvae can only be acquired through
active blood feeding, I believe
the nematode.belongs to the
M e r m i t h i d a e , a f a m i l y t h a t p a r a s i t i z e s a n u m b e r of i n s e c t
orders
(Welch,
nematodes
1965; N i c k l e , 1972;
fo u n d
were
n ot
P o i n a r , 1972).
included
Melanized
in t he E.
schneideri
infection prevalence data.
Horse Fly Parity and Host Restriction
Information
during this
collected on parity and
fat
body
deposits
study points to H. osburni as autogenous.
This
a g r e e s w i t h T h o m a s (1972) w h o c o n c l u d e d t h a t H. o s b u r n i is
autogenous
was
al s o
and present
present
Montana
August 6,
with
throughout
throughout
peak numbers
the
the
summer.
summer
This
in
species
southwestern
present between
Ju l y 27 and
1984 a n d . 1985.
The number of uniparous and nulliparous individuals was
s i m i l a r for H. r u p e s t r i s a l t h o u g h the n u l I i p a r o u s n u m b e r s
preceed
the
anautogeny
uniparous
of
this
individuals.
species.
This
H y b o m itra
may
tetrica
indicate
showed
a
difference betwe en the numbers of uniparous and nulliparous
flies collected,
but there was no difference in the date at
w h i c h e a c h g r o u p appear ed . No c l e a r d e c i s i o n c an be m a d e ,
45
but the larger numbers of n u l l iparous H. tetrica,
the early
e m e r g e n c e of H . r u p e s t r i s a n d H . t e t r i c a , a n d the p r e s e n c e
of peak numbers before mi d July,
are
anautogenous. Similar
anautogenous
The
cavity
is
of
fat
indicative
of
Autogenous
the
(R o c k e l ,
were
present
ability
obtained
in
of
or anautogenous
th e
1969).
The
for
abdominal
t he
species
in
(Lake and Burger,
individuals have a greater vo lume
bodies present in the abdominal
flie s
that these species
(1972).
bodies
question to be autogenous
1980).
results
species by Thomas
amount
suggest
of fat
cavity than do anautogenous
present
st u d y
showed
th a t
H.
osburni specimens had well developed fat bodies and suggests
t h a t this s p e c i e s is au t o g en ou s. No d e c i s i o n c o u l d be m a d e
on a u t o g e n y or a n a u t o g e n y of H y b o m i t r a r u p e s t r i s
a nd H.
tetrica based on fat body development.
A hindrance
body
l eve ls
large
of
number
dissection.
to
H.
of
these
and
species
dehydration
work
difference between
specimens.
rupestris
H.
tetrica
were
was
frozen
that
prior
a
to
The freezing damaged cellular detail and caused
irreversible
contrast
to properly determining the parity and fat
by
Thomas
ovarioles
However
of
body
(1972,
of
detecting
tissues.
1973)
frozen
This
that
specimens
mermithid
and
is
in
showed
no
and
fresh
filarial
jiematodes was not hindered by freezing.
Th e r e s t r i c t e d h o s t r a n g e of E. s c h n e i d e r i in M o n t a n a
is n o t w e l l u n d e r s t o o d an d w i l l
require
further research
46
b e f o r e an a d e q u a t e e x p l a n a t i o n can be offered. Th i s s t u d y
has s h o w n th a t H . t e t r i c a a nd H. r u p e s t r i s are the v e c t o r s
of the a r t e r i a l w o r m in s o u t h w e s t e r n M o n t a n a .
H y b o m i t ra
o s b u r n i , a l t h o u g h i n v o l v e d , m a y p l a y a s m a l l e r ro l e due to
its autogenous
egg production.
T h e B r i d g e r m o u n t a i n s p r o v i d e h a b i t a t fo r moose, elk,
and
mule
deer.
schneideri
(Hibler
1975).
All
three
in different
and
Adcoc k,
In Montana,
species
areas
19 7 1;
in
are
the
Worley
infected
with
E.
western United States
et
a l .,
1972 , W o r le y,
only mule de e r and moose have been found
i nf ec te d .
Why
elk
although
are
not
infected
sharing
the
same
parasite, vector,
not known.
with
the
geographic
arterial
areas
worm,
where
the
and other definitive hosts are present,
However,
is
a few speculations can be made based on
the r e s u l t s of thi s st u d y a n d e c o l o g i c a l
studies
of m u l e
d e e r an d el k in s o u t h w e s t e r n M o n t a n a . M u l e d e e r sp e n d the
winter
on
summer
the southwestern
in
females
the
eastern
select
s u b a l p i n e ar ea s
slopes of the Bridger Range and
slopes
forest
(P a c , 19 76),
habitat
(P a c , et al.,
and
avoid
and
adult
prairie
1984). The h o r s e
flies
and
were
fo un d c o n c e n t r a t e d in the h i g h e r a l t i t u d e s , in open fie ld s
adjacent to forested areas.
This
encounters
explaining
difference
between
the
low
in habitat
mule
selection
d e e r a nd ho r s e
prevalence
of
the
ma y 'decrease
flies,
infection
the
possibly
in Montana.
47
It is e q u a l l y
li k e l y that the p a r a s i t e
is p r e s e n t in l o w
n u m b e r s in this state. W o r l e y
et al. ( u n p u b Iished) b e l i e v e
that
the
Montana
is
located
at
northern
g e o g r a p h i c r a n g e of the a r t e r i a l wo r m ,
reports
of
its o c c u r r e n c e
in w i l d
l i m i t -of
the
s i n c e th e r e a re no
ruminants
in n o r t h e r n
Montana or adjacent portions of Canada.
E l k e x p o s u r e to i n f e c t e d t a b a n i d s m a y be m i n i m a l
to
n o n e . A l t h o u g h elk s h a r e w i n t e r g r o u n d s w i t h m u l e d e e r in
the northwestern slopes of the Bridger range,
the w i n t e r i n g g r o u n d s 4-6
the horse flies
observed
elk
e l e v a t i o n s ) to
exposure
to
w e e k s p r i o r to t h e e m e r g e n c e of
(Pac, personal
moving
from
higher
infested
they move from
communication).
wintering
windy
grounds
elevations,
geographic
Brazda
ar ea s
in
(at
(1953)
lower
thus
reducing
the
Gallatin
drainage in southwestern Montana.
Red deer in Scotland move during early spring to.avoid
emergence of tabanids and occupy "well winde d areas" for the
r e m a i n e r of the s e a s o n (Darling,
in th e B r i d g e r m o u n t a i n s n u m b e r s
personal
slopes,
communication)
a
foc us
of
1937). T h e e lk p o p u l a t i o n
about
200 a n i m a l s
(Pac,
a nd m o v e m e n t a w a y f r o m . t h e w e s t
infected
ta banids,
would
minimize
exposure.
Th e
Worley
ro l e of m o o s e in e l a e o p h o r o s i s is n o t k no wn , b u t
(1975) reported infections
Range area and Absaroka Mountains.
in moose from
These
the Bridger
large cervids show
c l i n i c a l s y m p t o m s i n d i c a t i v e of g r e a t e r s u s c e p t i b i l i t y or
48
exposure
to
unpublished).
resident
the
arterial
(Worley
et
a I .,
Further information about habitat selection of
moose
or
transient
u n d e r s t a n d t h e i r role in
Bridger
nematode
individuals
is
needed
to
E l a e o p h o r a t r a n s m i s s i o n in the
Range.
B e f o r e th e e c o l o g y of E. s c h n e i d e r i is u n d e r s t o o d in
s o u t h w e s t e r n M o n t a n a , v a r i a b l e s no t a d d r e s s e d d u r i n g this
study
(climate,
habitat
population movement,
hosts), need
to
be
diversity,
horse
need
longevity,
to
and
relationship
u n d er st o od .
be
studied
subjected
life
an d
de e r
and habitat selectivity by vectors and
and
evaluated.
t a b a n i d s i m p l i c a t e d as i m p o r t a n t v e c t o r s
worm
fly
cycle
between
to
parity,
studies
vectors
and
Species
of
of th e a r t e r i a l
feeding
before
primary
behavior,
the
subtle
hosts
is
49
SUMMARY
A s t u d y w a s u n d e r t a k e n d u r i n g June, July, an d August,
1984 a n d 1985, to i d e n t i f y p o s s i b l e t a b a n i d v e c t o r s of the
arterial n e m a t o d e Elaeophora schneideri We h r and D i k m a n s ,
1935
in s o u t h w e s t e r n Mon t a n a .
T a ba ni da e ) were
collected:
Thirteen species
Atylotus
insuetus
(D i p t e r a :
Osten
Sacken,
Chrysops ater M a c q u a r t , Chrysops exitans Walker, Chrysops
fulvaster
Osten
noctj.fjer
Osten
Hybomitra
l a s i o p h t h a l ma
(Bigot),
Sacken,
Chrysops
furcatus
S a c k e n , H y b o m itra
H y b o m itr a o p a c a
(H ine ), H y b o m itra
Walker,
c a p t oni s
Chrysops
(Marten),
(M a c q u a r t ), Hybomitra melanorhina
(Coquillett), H y b o m i tra osburni
rupest.ris
(M c D u n n o u g h ),
and
H y b o m itra
tetrica ( M a r t e n ).
Three Hybomitra species,
(H. osbu rn i, H. rupestris, and
H. t e t r i c a ) c o m p r i s e d 95% of t h e 1122 t a b a n i d s
Hybomitra osburni was most abundant during
the study,
Three
b o t h years of
followed by H. t e t ri ca , and H. r u p e s t r i s .
tabanid
species
were
found
st ag es of E. s c h n e i d e r i . One f e m a l e
infected
co ll ected.
with
three
first
infected
with
H. o s b u r n i
stage larvae
in 1984.
was
larval
found
Hybomitra
rupestris and H. tetrica were infected with first and second
larval stages.
Hybomitra osburni and H. rupestris are a n ew
host records for E.
schneideri.
50
P r e v a l e n c e of i n f e c t i o n w a s 0.5% for H . o s b ur n _i, 1.8 o
for H. r up est ris , and 1.6% for H. tetrica. Percent
for all
species dissected was
0.5% in 1984,
infection
'
0.9% in 1985,
and 0.8% for b o t h years.
Seasonal
distribution data
c o m m o n species.
E m e r g e n c e of H. o s b u r n i o c c u r r e d
J u n e an d p e r s i s t e d un ti l
was
observed.
were obtained for the three
In
in late
late J u l y w h e n a p e a k in n u m b e r s
co ntr as t,
H.
rupestris
and
H.
tetrica
peaked betwe en June 30 and July 19. The latter species were
present in low numbers the rest of the s um me r
Elaeophora schneideri
horse flies.
1985).
larvae were recovered from eight
Fifty percent
H. t e t r i c a , 37.5%
(1984,
(4/8) of the
infected flies were
(3/8) H. r u p e s t r i s , and 12.5%
(1/8) w e r e
H. o s b u r n i .
An unknown nematode species (Nematoda:
Mermithidae) was
fo u n d in 12.1% of all fli es d i s s e c t e d d u r i n g b o t h ye ar s of
the
study.
nematode
As
was
with
the
found
in
arterial
the
fat
nematode
bodies
and
larvae,
free
this
in
the
h a e m o c o e I of h o r s e flies d i s s ec te d. P r o p e r i d e n t i f i c a t i o n
was
hindered by the hosts
i m m u n e response
that resulted
in
the d e p o s i t i o n of the p i g m e n t m e l a n i n a r o u n d t he i n v a d i n g
n e m at od es .
Observations
dilatations
parity
of
of
the
fat
body
dissected tabanids
depots
allowed
a nd
determination
(oviposition history). Based on these data,
that H. osburni was
autogenous;
i.e,
ovariole
of
it appears
(haemotophagous
female
51
does n o t r e q u i r e a b l o o d m e a l for d e v e l o p m e n t of the f i r s t
e g g batch) w h e r e a s H. r u p e s t r i s a nd H. t e t r i c a a p p e a r to be
an a u t o g e n o u s .
Hybomitra rupestris and H. t e t ri ca , were the important
vectors of E schneideri in the Bridger Mountain
The most c o m m o n species,
important,
study area.
H. osburni was not considered to be
based on percent of infection and autogenous
egg
p ro d u c t i o n .
More
parity,
studies
are needed
ar e a s of e m e r g e n c e ,
to
determine
conclusively the
tabanid population movements
together with ungulate behavior during the horse fly season
to
understand
the
lack
of
the
arterial
populations in southwestern Montana.
nematode
in
e lk
52
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