TRANSFORMATIONS OF BUFFALO GNATS. 
13 
quire swiftly flowing water for their development. The full-grown 
larva of the largest species, according to Johannsen, measures not 
more than 15 mm. in length. The American species 
known to the writer measure from 12 mm. ($. pie- 
tipes) to 3.5 mm. (S. jenningsi). The larvae are 
generally subcylindrical, somewhat attenuated at the 
middle, and with a gradual dilation toward the anal 
extremity. In addition to the head there are 12 
rather indistinct body segments. 
In the larval stage the shape and number of the 
branches of the rectal gills seem to be good sys- 
tematic characters, not differing essentially among 
individuals of the same species. If the number and 
length of the an- 
terinal joints, the 
teeth in the 
mentum, and the 
character of the 
dorsal markings fig. 3.— mmuUum 
of the head are bracteatum. 
, , - t Antenna of 
also USed, the de- larva. Greatly 
termination of enlarged. (Orig- 
, , » inal.) 
half-grown 
larvse is possible. The larvse 
in their last stage can be corre- 
lated positively with their re- 
spective pupae by the dissection and study of the pupal filaments, 
which become fully developed under the larval skin. 
As the larvae of S. bracteatum and JS. jenningsi have not been pre- 
viously described, the follow- 
ing descriptions are given. 
DESCRIPTION OF LARVA OF SIMULIUM 
BRACTEATUM. 
The full-grown larva is from 6 
to 6.5 mm. in length. The general 
color varies from light yellowish- 
brown to grayish, with conspicuous 
brownish markings on the ventral 
surface. The antennae (fig. 3) are 
slender, 4-segmented ; * the second 
segment one and one-half times as 
long as the first; the third segment as long as the first; the fourth a short 
conical process ; the general color pale hyaline ; the first segment infuscate. 
The labial plate (fig. 4) is more strongly serrate than that of 8. venustum 
(fig. 5) : the apical margin rather convex; the middle tooth and each corner 
tooth very large. There are from four to five long bristles near the lateral mar- 
gin on each side. 
M. 
Fig. 4. — Simulium bracteatum. 
larva. Greatly enlarged. 
Labial plate of 
(Original.) 
Fig. 5.- 
lai'i 
-Simulium venustum. Labial plate of 
i. Greatly enlarged. (Original.) 
1 The writer differs from other writers in regard to the segmentation of the antennae. 
