&Reprinted
from the Proceedings
of the Entomological
Societyof Washington,Vol. 39, No. 9
December, 1937.&
THE
NOMENCLATURE
OF THE
CULICIDAE,
THORACIC
AND THEIR
IN THE
SETAE.
By W. H. W.
x
MedicalEntomologist,
U.S. PublicHealth Service.
We owe to 'F. W. Edwards &1&a great forwardstep in the
genericclassification
of mosquitoes,
basedin largedegreeupon
distinctionsfound in the thoracic chaetotaxy,which applies
equallywell to both sexes. The bristlesor setaeof the pleural
sclerites,as pointedout by him, are charactersof excellent
genericvalue. His early observations
have beenextendedand
confirmedby others,and assistmateriallynot only in defining
genericlimits, but in identifyingmany closelyalliedspecies.
In toomanyinstances
the practicingsystematic
entomologist
is calledupon to identify poorlypreservedfemaleadult mosquitoes,minus legs, wing-markings,and other charactersof
importancein'specificdifferentiation. Any characterswhich
will avail in sucha predicamentarewelcomed
by the taxonomist.
The distinctionspointed out by Edwards are of this sort, as
evenin badlydenudedspecimens
they can be madevisibleby
suitable treatment.
Recentlydevelopedmethodsof collectingadult mosquitoes,
suchas variousformsof light-traps,usuallygive catchesin a
relativelypoorstateof preservation.The majorityof specimens
whichhave beencollectedfrom airplanesservingSouthAmerican airportswerein rather poorcondition. Sometimes
it is of
extremeimportanceto know,as nearlyas the materialpermits,
the species
of mosquitotakenin airplanes
comingfrom yellow
feverareas. In many cases,if the genusof the specimencanbe
determined,a closeguesscan usuallybe made as to the species,
if the fauna of the regionfrom whichit comesis well known.
In attempting to use the excellent method devised by
Edwards, the lack of uniformity of nomenclature'used by
authors
whohavegivenlaterdescriptions
of thep.leuralsclerites
and their setaebecameapparent. Further inquiry disclosed
a
deplorable
situation,whichshouldbe rectifiedif the methodis
to proveuniversallyuseful.
XFrom the GorgasMemorialLaboratory,H. C. Clark, Director,Panama
City, Republicof Panama.
PROC.ENT. SOC.WASH., VOL. 39, NO. 9, DEC., 1937
No attempt is made in this paper to amend current conceptions regardingthe homologiesof the variousscleritesof the
mosquitothorax. Its conclusions
are offered,not as the studies
of a trained morphologist,but as the findingsof a taxonomist
who, in the courseof his daily work, usesthe systemof differentiation workedout by Edwards. It is hopedthat, if the
situation with regardto nomenclatureis disclosed,more general
agreementas to terms will result. Even if this consummation
doesnot occur, the paper may have value as a reference-work
for all those who find the pleural setae of use in mosquito
taxonomy.
The morphologyof the dipterousthorax, and the homologies
of its sclerites,have been the subjectof exhaustivestudy by
insect morphologists,of whom Crampton &2&&3&has done
relativelyrecentworkin the nematocerous
forms. Whilehis
work has been concernedlargely with forms not particularly
closelyrelated to the mosquito,his findingshave beenof great
servicein clarifyingour conceptions
of the morphology
of the
pleural scleritesof the culicid thorax. They thus serve as a
basisfor a nomenclatureresting on a sure foundationof morphology.
THE
STRUCTURE
OF
THE
CULICID
THORAX.
At the risk of seemingunduly elementary,but in order to
orientatethe reader,whomay haveforgottenmostof hisinsect
morphology,
it may be wellto reviewbrieflythe structureof the
pleuraof the dipterousthorax, so that the namesusedlater for
the variousscleriteswill have significance.
The thorax of a dipterousinsectis composed
of three segments, prothorax, mesothorax,and metathorax, in order from
the head to the tail.
Those authorities who have studied the
subjectbelievethat in their primitive conditionthe sidesof the
thorax were composedof three plates, forming the lateral
portionsof these three thoracicsegments. Each of the three
lateral plates is known as a pleuron &theplural of which is
The threelateral platescorresponding
to the three
segmentswere each divided into two sclerites,an anterior one
calledthe episternum,
and a posteriorone calledthe epimeron.
These terms are usedwith the prefixespro-, meso-,and meta-,
to indicatethat they' are parts of the prothorax,mesothorax,
and metathorax.
Sometimes these sclerites were divided into
an upper and a lower portion, a conditiondesignatedby the
prefixesan- and kat- &Gr.ana- up, kata- down&. Thus the term
mes-an-episternum
meansthe upperportion&an&
of the anterior
sclerite &episternum&
of the mesothorax &indicatedby the
prefixmes-&.Other termsare compounded
in the sameway.
A complicationentersin thoseinsectswhichare winged,and
PKOC.ENT. SOC.WASH.,VOL. 39, NO. 9, DEe., 1937
243
in which thereforecertainparts of the thorax are enlargedto
give room for the wing-muscles.The plates overlying these
musclesare enlargedand the other platesmay be correspondingly reduced. This is true of the Diptera as a whole,in which
the mesothoraxis greatly enlarged.
In some instances, this increase in size of the mesothorax
proceededso far that the scleritesformingthe prothoraxand
metathorax, anterior and posterior to the mesothorax,are so
reducedand fused that they are difficult or impossibleto
distinguish.
The parts of the dorsumof the thorax neednot detainus here,
exceptto notethat the dorsumof the prothoraxis knownas the
pro.
notum,andis dividedinto twoportions,
anteriorandpos-
terior. In primitive Diptera, as in someTipulidae &crane-flies&,
the two portionsare dorsalin position,and are separated
by a
well-marked
suture.
In mosquitoes
a secondarycomplicationarisesin assigning
morphologicallycorrect terms to the parts of the prothorax.
The anterior and posterior pronotum, normally dorsal in
positionin primitive Diptera, have migrated venttad &towards
the sternum&and caudad &towardsthe tail&. These parts in
their altered position apparently form portions of the lateral
platesof the anteriorportionof the thorax.
The scleritesof the pleura &sides&
of the anteriorsegmentof
the thorax &theprothorax&,
whichare termedthe
and the proepimeron,
are thuscrowdeddownwardsand reduced
to insignificantproportions. Their placesare occupiedto a
largeextent by the partsof the pronotum,whichhavemigrated
ventrally.
This migration of the dorsal portionsof the prothorax has
been overlookedor disregardedby several authorities; thus it
has followedthat the true posteriorpronotum,a dorsalpart of
the prothoracicsegment,has been called the
which by definitionis the posteriorportion of the prothoracic
pleuron,a lateralpart.
The corresponding
anteriorscleriteof the prothoracicpleuron
has been called the propleuron,but morphologicallyit is the
proepisternum,
the anteriorsclerite&muchreducedin
of
the prothoracicpleuron.
No referencehas been found, in a limited search, to the term
as appliedto mosquitoes.Many authoritiesuse
thetermin connection
withthesetaefoundon'thispart,calling
them the
It wouldseemthat
beingmorphologically
significant,is the better term.
The anterior portion of the pronotum, normally dorsal in
positionand part of the prothoracicsegment,has likewise
migratedventrally,,and has divided into two lobes,more or
lesscompletelyseparated. This migrationand separationof
244
ENT. SOC. WASH., VOL. 39, No. 9, DEC., 1937
theselobes,oftencalledthe
hasproceeded
farther in the Anophelinithan it hasin someof the other Culicidae. In the genera
and
the prothoracic
lobesare very large,and nearlycontiguous
dorsally.
The scleritesof the pleura of the metathoraxare of little
importancetaxonomically,
with the exceptionof the meron.
This is the smallscleriteat the baseof fhe mes.
epimeron,posterior to the middle coxa,and is known also as the meso-merocoxa,
and incorrectly as the
metasternal
The
positionof its uppermarginwith reference
to the baseof the
hind coxa servesto differentiate the tribe Megarhinini and the
tribe Sabethini &ofDyar& from the other three tribes of the
Culicinaerecognizedby him. &Exception:
Haemagogus,
which
is Aedine, but has the base of the hind coxa in line with the
uppermarginof the meron,as in the Megarhininiand Sabethini.& Crampton&2&
hasshownthat the meronis derivedfrom
the posteriorhalf of the middlecoxa,by a process
of fissionand
migrationdorsally.
TERMINOLOGY
OF THE
PLEURA
AND
THEIR
SETAE.
To show the confusion which exists in the nomenclature of the
pleuralsclerites,and the consequent
confusionin the terms
appliedto their setae,two tablesand two figureshave been
prepared.The firsttableliststhe termsappliedto the pleural
sclerites,accordingto Edwards&1&,&4&,Freeborn&5&,Dyar &6&,
Patton &7&,Matheson &8&,Root. &9&,Shannon &10&,Christophers&11&,
and Gater &12&.
The secondtable lists the terms applied to the setaeof the
pleuralsclerites,according
to the sameauthorities. The list of
terms appliedto the setaeby Patton and Evans is taken from
the first volume of their work &13&.
The first figure has the sclerites named in the first table
indicatedby .numbers,
whichcorrespond
to the numbersin the
left-hand column of the first table. Reference to these numbers
will enable the reader to learn the various terms which have been
appliedto the sclerites.
The secondfigureshowsthe pleuralsetae,and is composite,
as no one speciesof mosquitopossesses
all the setaeshog.
n in
the diagram. The samesystemof numbersand referenceto
the tableof setaeis used. The numbersin the secondfiguredo
not correspondto those in the first figure, but refer to the
second table.
In the first table &ofsclerites&,it will be noted that the mes-
epimeron&No.6&is the onlytermusedin commonby all the
authorslisted. The proepisternum&No.2&is knownunderfive
different names. The anterior pronotum &prothoraciclobes.
No. 1& is likewise designated by five different terms. The
PROC.ENT. SOC.WASH., VOL. 39, NO. 9, DEC., 1937
245
I. Nomenclatureof scleritesof pleuraof Culicid thorax. 1. anterior
pronotum;&prothoracic
lobes&.2. proepisternum.3. posteriorpronotum.
4. mesanepisternum. 5. sternopleuron. 6. mesepimeron. 7. roeton.
8. prealar area. 9. metepisternum. 10. metepimeron. 11. meteusternum.
posteriorpronotum
No. 4& is known
under three different names.
In the secondtable &ofsetae&there is a little more agreement
in nomenclature,as four terms are used in commonby all the
authors.
SOME
NECESSARY
CORRECTIONS
IN
TERMINOLOGY.
In theparagraphswhichfollow,certainerrorsin nomenclature
made by the authorscited are corrected.
Edwards&4&
usesthe terms
&singular&
and
&plural&
for the sclerltesof the sidesof the thorax. While not
absolutelyincorrect,
being a secondary
meaningof
&asthe latter term is usedby entomologists&
accord-
ing to Webster,mostmorphologists
use the word
&singular&
and its plural form
Edwardsalsousesthe term
for the posterior
pronotum,in accordance
with earlierconceptions
of thissclerite;
he statesthat this use of
is probably incorrect.
246
PRoc. ENT. SOC.WASH.,VOL. 39, No. 9, DEC., 1937
PROC-
SOC.WASH.,VOL.
NO.9, DEC.,1937
247
548
pRoc.ENT.SOl3.WASPI.,
VOL.39, NO.9, DEC.,1937
PKOC.ENT. SOC,WASH., VOL. 39, NO. 9, DEC., 1937
249
Root &9&usesthe term
for the mesanepisternum, but Crampton &3&statesthat this designationshouldbe
given to
entire flanksor pleura of the
Shannon &10&also uses the term
for the
mesanepisternum.
Matheson &8&states &p.b, line 15&,that the pronotal setae
are located on the posterior margin of the
evidently designatingthe posteriorpronotum as the pronotum.
On p. 11,line16,hestatesthat the pronotumis
by
the two prothoracic
Patton & Evans &13&,
in Fig 163, label the setaeon the proepisternum&propleuron&
as the
setae. There is
no justification either on morphologicalgrounds,or in entomologicalusage,for this designation.
Patton, in Fig.
of his secondvolume &7&,designates
correctly the scleriteon which the so-called
setae
occuras the
Severaltypographicalerrorsmar the accuracyof his Fig.
The mer9n is incorrectlydesignatedthe
and
vice versa. The meseusternum,
by definition,shouldbe a part
of the mesothorax,but it very evidently is a part of the metathorax, and shouldbe designatedthe meteusternum.
The legendbeneaththe figure containsa misprint, in which
the sclerite
is calledthe
whenit is
evidentlythe
The true
is labeled
Dyar &6&givesa figure,No. 1 on Plate I, page 473, of the
lateral view of the thorax. In this figure,someof the pleural
setaeare named. The scleritesare not designated. It has been
necessary,
therefore,in drawingup his list of termsfor setaeand
sclerites,to refer to the designations
given in his table of tribes
and generaon page4. The
of figure 1 on Plate
I rendersthis table of generauselessto the occasionaltaxonomist, whomay have no knowledgeof the locationof the various
setae mentioned in the table.
The locationis not shownof the
setae&p.6,
line 14&,which are incorrectly called the
setae in
the diagram;they shouldbe designatedthe
setae. The prothoraciclobes &anteriorpronotum&are figured,
but not designated.The propleuralsetaeare shown,but also
not designated,althoughthey are mentionedin the table &p.6,
line 26&. The positionsof the
setae &p.7,
'
r
line 14&andof the
seta e &p.6, line
3 fom
bottom&
are not figured.
The dichotomy&No.9, p. 6&indicatingthe separationof the
genusMenolepixfrom genusMiamdyia,if worked backwards
throughthe precedingdichotomies,
is incorrectif the characters
of the genusMenolepixare correctlygiven on p. 66. Thus:
2S0
PROC.ENT. SOC.WASH.,VOL.39, NO.9, DEC.,1937
2. Nomenclature
of pleuralsetaeof Culieidthorax. 1. anteriorpronotal &setaeof prothoraciclobes&.2. proepisternal.3. posteriorpronotal.
4. spiracular.
postspiracular. 6. prealar. 7. sternopleural. 8. mesepimeral.
&9&Wing-scales
narrow. &7&Lower sternopleural
setaeextending asfar as,usuallyaboveupper margin of lateral metasternal
sclerite. &6&
Spiracularsetaepresent. &4&
Prealarsetaepresent.
&3&
No [posterior]
pronotalsetae;prothoracic
lobesnotwidely
separated.
On page66 it is stated:
setaepresent,prothoracic
lobeswidely
in direct contradictionto the characters
givenin the key &second
half of dichotomy3, p. 6&.
SUGGESTED
TERMINOLOGY.
As an approachto an exactnomenclature,
basedon morphology,the followingtermsfor thepleuralsolerites
aresuggested
as
desirable. The numbersprecedingthe terms apply to the
numbersin Figure l, indicating the location of the pleural
solerites. Thesetermsare givenin the legendbelowthis figure.
&1&anteriorpronotum;&prothoracic
lobes&
&2&proepisternum
&3&posteriorpronotum
PROC.ENT. SOC.WASH., VOL. 39, NO. 9, DEC., 1937
251
&4&mesanepisternum
sternopleuron
&6&mesepimeron
&7&roeton
&8&prealar area
&9&metepisternum
&10&metepimeron
&11&meteusternum
A similar terminologyfor the setae of the pleura is listed
below. The numbersprecedingthe termsapply to the numbers
in Figure 2, indicatingthe pleural setae, and these terms are
giv.enin the legendbelowthis figure.
&1&anteriorpronotal;&setae
of prothoraciclobes&
&2&proepisternal
&3&posteriorpronotal
&4&spiracular
&5&postspiracular
&6&prealar
&7&sternopleural
&8&mesepimeral
Where the terms in earlier use are more familiar, or are
preferred by the individual worker, it is recommendedthat
thesebe given also in parentheses,after the correctmorphologicalterms,in futurepublications.If the oldertermis simply
an alternativedesignation,it may be enclosedmerely in parentheses. If the term is morphologically
incorrect,and therefore
a misnomer,it may be enclosedin parenthesesand quotation
marks. Instancesin which this procedurewould be extremely
useful are: anterior pronotum &prothoraciclobes&,posterior
pronotum
meron
metasternal
CONCLUSION.
It is hopedthat the tablesand figuresgivenin thispaperwill
be of assistanceto entomologistsand others interested in
mosquitotaxonomy. They may be usedasreferences
in studying the worksof the variousauthorities,and as guidesto the
properuseof termsin futurepublications.
That somesuchanalysisas forms the sub.}ectof this paper
seemsnecessary,in order to guard against further errors and
confusion,ought to be self-evidentfrom the chaoticsituation
disclosedregarding the nomenclatureof the pleural sclerites
and their setae.
252
1.
2.
3.
4.
5.
6.
7.
PROCEH'T.SOC.WASH.,VOL.
H'O.9, DEC., 1937
Edwards,F. W., 1921. Bull. Ent. Res. XII, pp. 205-362.
Crampton,G. C., 1925. Ann. Ent. Soc.Amer. XVIII, pp. 49-74.
Crampton,G. C., 1925. Ins. Ins. Mens. XIII, pp. 197-213.
Edwards,F. W., 1932. GeneraInsectorum,Fascicle194,p. 4.
Freeborn,S. B., 1926. Tech. Bull. Univer. Calif. III, pp. 333-460.
Dyar, H. G., 1928. The Mosquitoesof the Americas,pp. 6-7 andp. 473.
Patton, W. S., 1930. Insects, Ticks, Mites and VenomousAnimals of
Medical and Veterinary Importance,Part II, pp. 69-72.
8. Matheson,R., 1929. The Mosquitoes
of North America,pp. 6-11.
9. Root, F. M., 1929. in Animal
Hegner, Root, Augustine,
p. 477.
10. Shannon,R. C., 1931. Proc.Ent. Soc.Wash.,XXXIII, p. 158.
11. Christophers,
S. R., 1933. The Fauna of British India, Diptera, Faro.
Culicidae,Tribe Anophelini,pp. 15-17.
12. Gater, B. A. R., 1935. Aids to the Identificationof AnophelineImagines
in Malaya, pp. 24-27.
13. Patton,W. S., andEvans,A.M., 1929. Insects,Ticks, Mites andVenomousAnimalsof MedicalandVeterinaryImportance,Part I, p. 275.