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Psyche 13:11-21, 1906.

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1 9061 MOUTH PAå£~S'O MOSQUITO LARVAE 11 MOUTH PARTS OF MOSQUITO LARVAE AS INDICATIVE OF HABITS. BY EVELYN G. MITCHELL, WASHINGTON, D. C, The larvae of the Culicidae follow the usual rule that a difference in the structure of the mouth parts is correlated with a corresponding difference in their food habits. This fact first forced itself upon the writer's attention when studying the habits of the Louisiana species, while making drawings and dissec- tions for Dr. J. W. Dupree, and was later confirmed when making dissections and drawings of larvae of additional species for Dr. Howard's forthcoming mono- graph of this family.
These larvae fall into two categories, viz.: I. Insectivorous, which, like Meg- arhinus and Psorophora, normally prey upon small aquatic larvae; and 2. Non- sectivorous, like Culex, which feed on Euglena and other protozoa, bacteria and vegetable matter; while between these groups are two others, somewhat interme. diate, viz.: the Uranoiaenia and Anopheles groups. That the differences in habits are correlated with marked differences in the structure of the mouth parts will be seen by the following critical comparison of the types of these four groups : Fig I.
Mandible of C. taeniorhynchus.
Pnrhr 13:11-19 (1%). hup Itpsycht enlclub orgt13113-011.htd



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PSYCHE
MOUTH BRUSHES. 1
Hairs slender, veryi Same as I.
numerous, slightly pec-
tinate or simple, project-
i n g forward ; adapted
for making a current to-
ward the mouth. 1
-1
MANDIBLES.
(See Fig. 1.)
Biting Part. (D.)!
Comprises 1 - 10 of Same as I, e x c e p t whole mandible. Ante- that the anterior tooth rior tooth heavy, rather is especially heavy anc blunt, not sharply dif- blunt, and the teeth a1 ferentiated from the base of primary tooth t h re e following teeth are heavy and blunt. (of which the third is
largest and 1 o n g e s t),
which do not recede
sharply ; two t e e t h ,
usually sharp and slen-
der, at base of primary
t o o t h. S om e short,.
blunt teeth on ectal side'
of mandible below main
group and not project-
i 11 g so far. Arrange-
ment primarily for
crushing.
Arficulaie serrate
spine. (I.)
Sometimes ~"P'Y, very 1al-g~
sometimes bluntly ser- tooth, seme at base rate, narrow or broad,
differentiated frox
long Or
but 'lever the four followillgshar~
so wide as biting part,
teeth . do 1 arrange
on entalsideandproject- mellt 'as large, tho+ ing
biting part ;
0 t so heavy,
a s the
four to twenty serrate-
No sma,
plumose, slender mova- articulate spines. ble s p i 11 e s below it.
Movement evi d e 11 t 1 y
like a chopper.
Lateral Comb. ((;.)I
111. ANOPHELES.
Same as I.
Many, never v e r y The three uppermos-
Heavily chitini s e d
about 1-6 of whole bulk.
Anterior tooth sharp,
conspicious, not sharply
differentiated from the
three s m a 1 1 e r teeth
which are placed so that
their tips form a sharp-
ly receding line ; t w o
rather blunt teeth atop
of the primary tooth at
its base; a bunch of
m an y short, s 11 ar p
spines and small teeth
below last well deve-
loped tooth. Arrange-
ment for tearing 01
crushing.
heavy, elongate, some-
what curved, triangular
Stout, heavy, chitiu-
sed hairs, serrate 011
iistal part ; held at
ight angles to head or
olded under. Adapted
or seizing.
spines heavy and strong
1 y chitinis e d ; b a s e
Very heavily chitin-
sed, forming about one-
ourth of bulk. Anter-
or tooth (especially in
^sorophora) very long,
~ointed, well separated
rom rest, heavy ; other
eeth sharp. ~rran~e-
nent for tearing. Much
nore irregular than in
he foregoing f o r m s.
itout accessorv snine
, a
)n side of base of prim-
iry tooth, ectal aspect,
A heavy, wide, flat,!
Not present.
irregularly serratespine;
below it are two articu-i
late, flat, narrow spines'
with hairs in the serra-1
tions. , I
The three uppermost
Long, curved, heavy,
spines not conspicious-
immovable spines, es-
ly heavier than the rest. pecially heavy and finely



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margins to the ectal end
of the cephalic (or top).
margin with which it
forms an acute angle.
p 1 at e s, set with flat
sides parallel on a chit-
inised ridge ; somewhat
movable in a line paral-
lei to base ; base corn-
ing in a curve from a
point half way between
the lateral and mesa1
Marginal Comb. (F.)
Ei t h e r fifteen t o
twenty, more or less,
s i g m o i d, immovable
spines, with the two or
three nearest base of
lateral comb more or
of papillae b e a r i 11 g
single, feathered hairs
i
less plumose ; or a row1
or very short hairs (in1
the latter case the pap-\
illae are moved over the
top of the mandible on-
to the ental aspect).
heavy, not forming so
acute an angle as in I,
None
Base as in 11.
Projection belozv la.^i
tooil?. (14: .)
but, like 111, at not so
great an angle with basel
of primary tooth, nor so
far forward as in IV. 1
S;mpIe articulate
S])iiie~. (H.)
About size of bitingi A h u g e , shaples: part and resembling a projection about o 11 e turtle's head with open
jaw; a tuft of small
hairs on top of " head,"
one on the upper line of
" lower jaw,"aline, more
01- less, along back and
side of "neck." A small,
heavily chitinised pro-
jection below.
Two fringed plate;
near base of biting par
and four or five 1011;
fringed hairs set at :
distance from these am
against the upper em
of the base of the latera
comb.
fourth s i z e of wholf
mandible, bearing 01
the lateral margin a rov
of short, hooked hair;
a 11 d two bunches o
s 1 i g h t 1 y longer hair
on the side, joined witl
projection below it.
On latero-cep h a 1 i c
angle below upper end
of base of lateral comb;
two slender, crescent-
shaped.
A distinct, rounde<
projection, having o I
top a small papilla witl
a few minute hairs. N1
projection below.
Four large, flat, shar]
spines, the outer one,
about one-third longe
than the inner. whicl
are a little fringed, tape
Four large, flat, shar
spines, dilated at base
outer twosmooth, rathe
sharply bent near base
inner two sigmoid, mor
IV.
set in Psoyophora, few
is compared with other
o r m s (especially in
~sorophorn), their base
orming almost a right
ingle with top of man-
iible, and pushed for-
ward almost to base of
irimary tooth.
None.
Projection below last
teeth aborted into a few
irregular projections in
Psorophora; joined with
the next lower pojec-
tion and larger in Megar-
?zifius, having a projec-
tion below it in Psoro-
phora.
A single, heavy,sharp
curved spine in Psoro-
phora; two rather slen-
der spines with three or
four plumules in Megar- ,




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PS YCHE
[February
Tuft A.
(See Fig. 2.)
A large tuft of long
or short movable hairs
at apex, often a line ex-
tending down the chiti-
nous strip toward the
double spines.
Longpatch of short hairs
Some slender, some
spine-like or thickenec
and split, on side oj
c h it i 11 strip farthesi
from pulpus. Usuallj
a few hairs on sidc
next pulpus.
Labial Plate.
Nine to 33 teeth; ir
general tending to 15
23 rather fine, evenlj
graded teeth exceptir
t he 1 o n g breathing
tubed species where thf
teeth show a tendency
to irregularity difficul
to describe but easy t(
see.
Of immense, flat setai
serrate on one side.
Same, but the hair
not thickened but close
ly set.
Coarse, bluntl:
rounded teeth, 11 ii
number. General shap
of plate ellipsoidal,
regular outline.
A row of papillae
bearing several shori
hairs each, extending
along top of body oJ
maxilla from end near-
est palpus about hali
way; a row of erect,
hooked hairs for aboui
the same distance, con
tinued into a thick mass
of hairs curling down
across the top ; a bunch
of short spines at end
farthest from palpus.
Many short, curvec
hairs in groups on up
per % next pulpus, se
thickly on upper mid
die $3 and upper anc
lower 1/ farthest from
pulpus.
Coarse, much sepa
rated, rather sharp, ir.
regular teeth, 9. Not 2
regular curve.
IV.
In Psorophora a row
of short, flat, triangular
spines along the apex
from base of pulpus,
curling over and con-
tinued in a patch half
down the side on the
half away from the pul-
pus, at the third far-
thest from the pulpus
these snines are verv
large, hooked and in
3 rows. In Megarhinus
a large patch of straight,
short spines and one
long, slender spine on
side of emargination
nearest pulpus; a dou-
ble row of large, hook-
ed spines on farthest
elevation, continued in-
to a graded row of
straight spines down
mesa1 margin, and I
hair-like spine.
Wanting.
Teeth tend to coarse;
ness and to have center
and end teeth largest in
Psorophora.




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19061 MITCHELL-MOUTH PASTS OF MOSQUITO LARVAE 17 Fig. 2.
Maxilla of C. salinarius.
As the above comparative scheme shows, in insectivorous forms the principal appendages of the mandibles and maxillae are sharp, heavy and fitted for tearing ; or stiff, spiny, immovable, and adapted for holding the struggling prey. The cor- responding appendages in the non-insectivorous forms, whose food is micro- scopic, are more blunt and better adapted for crushing ; or are, slender, more or less movable, and fitted (as the A tuft of the maxilla) for aiding the mouth brushes to draw food into the mouth ; or (as the smaller hairs of the maxilla) for a sieve. The plates of the lateral comb on the mandible are movable in the plane of the base, and, so the writer thinks, help to direct food toward the crushing portion, the other comb acting as a sieve and the remaining appendages being sieves or tactile organs. , .I .A- Anopheles and Uranotaenia seem t~ exactly corresp&d with neither of the foregoing groups. P.oro$hora we know will prey on larvae of other species and even turn cannibal if hard pressed.
Megarhinus will do the same.
Psorophora,




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I 8 PS YCHE- [February
however, can exist, temporarily if necessary, on a diet of Eugletza, though it does not thrive on this, as Dr. Dupree proved when the writer was with him. Anoph-
eles will bite each other viciously, tearing off the hairs so frequently that perfect specimens of the larvae are to be obtained only by isolation ; will devour skins, occasionally kill other larvae and always eat any which die. Uranotaenia is sup- posed to have the same habits as Ano//;eZes, save that, whereas Ano/heZes skims the surface, Uranotaenia feeds just below. From the shape of the mouth parts, however, the writer would judge the latter to be distinctive in its method, a vege- tarian and also feeding on minute crustacea and the like. In the non-insectivorous groups are two distinct types of mandible and max- illa. The facts on hand suggest that these are associated with two types of breathing tubes and antennae, as well as with different habits of feeding. The author hopes to make further observations when opportunity offers, not having hitherto paid special attention to this point. The group with long breathing tubes (M. atratus, C. $@/ens, C. terntans, C. C. resfuaus, C. salinarius), feed with the tubes almost continually at the surface, sailing about by the movement of their mouth-brushes, and leaving the surface only when disturbed. Their food evidently floats freely, and is drawn in by the currents set up by the brushes. In these forms the antennae have very large and plumose tufts; the marginal comb on the mandible is reduced to papillae bearing a few hairs and moved over the top somewhat onto the opposite side from the lateral comb. The maxillae are of a pointed, sub-conical form, with the terminal hairs freely movable and very long, many of them as long as, or longer than, the body of the maxilla, with several long-plumose hairs in the tuft, which is mostly composed of single hairs. The plumose hairs are probably sensory, while the function of the simple hairs is probably only to brush in food. C. discolor forms an apparent exception, having this type of maxilla and mandible, but when one considers that, although he feeds at the bottom, he lies on his back most of the time, and feeds on floating matter, his not feeding near the surface makes no great difference.
C. jamaicencis, 3 musica, and 3'. vaftpes also belong to this type, though the latter two can stay at the bottom a long time if disturbed. The bottom feeders, as far as known, have straight, stubby antennae, gen- erally bare of spines, with one hair or a very few simple hairs in the tuft. The mandible has the marginal comb well developed, the maxilla is a flattened cone, the terminal tuft of stiff, straight hairs, which are rather short, is evidently for use in brushing over the debris at the bottom, where the very long, slender hairs would be a disadvantage. C. dupreei, with its very short antennae, and its bottom feeding habits, is a very good example. C. trife/@s lives in hollow trees, and



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feeds at the bottom of the hollow ; the antennas, mandible and maxilla are all typical of this habit. To have such a type of mouth parts the larvae need not necessarily be bottom feeders ; they may brush over the sides of a tank or float- ing or half-submerged objects, grasses, spirogyra, etc. There are maxillae which
seem transitional, though there are only the two types of mandibles ; and there are in some maxillae peculiar developments of the lateral hairs, which are prob- ly related to some peculiar habit of feeding, or character of food. Among the non-insectivorous larvae is one, Deinocoties cancer, that so dis- tinctly and strikingly, in several respects, departs from the ordinary type of larvae as, so the writer believes, to justify its being placed in a new sub-family, DETNO- CERITINAE, The head is sub-circular and is characterized by an angular projec- tion of the chitin caudad of the base of each antenna. This lateral angle forms a groove, running on the ventral side of the head, in which groove the basal por- tion of the lateral aspect of the mandible moves in and out, so as to be visible from above, a thing which, so far as the writer knows, exists in no other culicid larva.
The anal gills are entirely absent.
The maxilla affords no striking departure from the type, it being in general that of a larva feeding on floating objects. The labial plate is different from others in that the teeth, instead of being broad at the base and coming gradually to a distinctly narrow point (with but few exceptions), are but little narrowed until they abruptly point off, are very long for their width and, especially, are all separated from each other by a space of more than their width, while the two basal are very much longer than any but the central (which is about twice the length of the rest), and are set caudad from the base of the next by about their own length. The mandible is like no other (see fig. 3). The biting part is three, weak
teeth, not heavily chitinised (the whole larva is almost transparent), set in a de- cidedly receding row. Normally, the non-insectivorous larvae have four teeth, not receding very much. The projection just below the teeth, instead of being about twice as long as wide, and having an "under jaw," is fully six times as long as wide, the tip pointed and bent down for about one-fourth the length. The mar- ginal comb is nine short, sharp, stright spines. The chopper-like part is a sort of narrow hook, finely serrate at the distal end. There is a third articulate spine, shorter than the others, between the usual two, an odd number in this place being very unusual. But the distinguishing feature is the caudal portion of the lateral aspect. In other mandibles, so far as the writer can ascertain, this part forms an even, continuous curve with the rest of the mandible body and bears a very few minute spines, or (as in Ano/heZes), a row of fringed hairs. In D. cancer this portion of the mandible is produced, and in shape is like the thumb held on a plane with the hand and flexed at the second joint. The part flexed in the man-



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PSYCHE
[February
Fig. 3.
Mandible of Beinocerites cancer
dible seems to be rather soft as, although no suture can be seen, the projection is capable of a slight flexion and extension. The projection works in the trough formed by the angle of the head. Instead of the usual minute spines at this point there are about twenty-five long, slender spines placed in a group with their bases well separated. They are apparently somewhat movable. The function is diffi-
cult to imagine.
The adult is distinguished from all others by the unusually long antennae