TBANSFORMATIONS OP BUFFALO GNATS. 
15 
The rectal gills (PI. IV, fig. 5) are three-branched, each lateral branch bear- 
ing six lobes and the middle branch five, as a rule. This is a smaller number 
of lobes than is found in venustum (PI. IV, fig. 9), which 
has seven or eight on each lateral branch. 
The caudal sucker bears from 70 to 75 rows of hooks. 
The larvae were taken by the writer from a fair- 
sized stream near Spartanburg, S. C, in August, 
1913, and were separated from the larvae of other 
species by the number of branches of the pupal 
filaments (formed underneath the larval skin) and 
determined from adults reared from them and com- 
pared with the type. 
EXTERNAL AND INTERNAL STRUCTURES OF THE LARVAE. 
The head is more or less quadrangular in shape 
and very chitinous. The eyes have become reduced 
to mere pigment cells, in the shape of two irregular 
black blotches, situated on each side of the head. 
In addition to the usual mouth parts, the head 
bears a pair of peculiar fan-like organs, situated 
one on each side at the anterior end. The rays or 
cilia of the fans are attached at 
the base each by a strong peduncle 
and range in number from 30 to 
60 according to the species. On 
the inner margin of these cilia are 
fringes of short hairs interspersed with minute 
teeth. As the number of cilia varies in individuals 
of the same species, they are not very reliable 
specific characters. The fans, acting as strainers, 
catch the microorganisms on which the larvae feed 
and sweep them into the mouth. 
The antennae (figs. 3, 7, 8, 10, 11) are situated at 
the sides <©f the head, on the dorsal surface toward 
the cephalic end, just below the base of the fans. 
They are slender, and in the species examined, 
naked. Johannsen says " The antennae are appar- 
ently jointed * * * the first joint twice as 
long as the others taken together; the second, 
slender cylindric * * * the third joint a short 
pointed process at the apex of the second." Miall 
says "Small three- jointed antennae" and gives a 
figure in which the antennae have three long joints 
and lack the short pointed process forming the last joint. Of 
the five species dealt with in this paper, the larvae of Simulium 
venustum (fig. 8), S. pictipes (fig. 10), and S. bracteatum (fig. 3) 
Pig. 10. — Simulium 
pictipes. An- 
tenna of larva. 
Greatly en- 
larged. ( Orig- 
inal.) 
Fig. 11. — Simulium 
vittatum. An- 
tenna of larva. 
Greatly en- 
larged. (Orig- 
inal.) 
