14 
BULLETIN 329, U. S. DEPARTMENT OF AGRICULTURE. 
The head (PL III, fig. 7) is light brownish-yellow in color, heavily marked 
with brown on the lateral margins. The dorsal markings of the head are ar- 
ranged in the form of a long central irregular blotch, with 
two adjacent blotches extending diago- 
nally on either side. 
The mandibles are similar to those of 
S. venustum (fig. 12), but darker in color. 
The maxilla? are infuscate and very hairy ; 
the proximal portion of the maxillary 
palpus is dark brown, with a few sparse 
hairs ; the distal end transparent, bearing 
a few conical processes. 
The rectal gills (PI. IV, fig. 7) are 
simple, three branched, somewhat pointed 
toward the distal end, and are curved 
backward cephalically when extended. 
The caudal sucker bears from 60 to 70 
rows of spines or hooks (fig. 6). 
The larvse were taken by the writer from several fig. 7.— SimnUum 
streams in the vicinity of Spartanburg, S. C, from in'tenna^f 
June to October, 1913. They were separated from 
the larvse of other species by the number of the 
branches of the pupal filaments (formed under- 
neath the larval skin) and determined from adults reared from 
them and compared with the tj^pe. 
I 
1 
Fig. 6. — Simulium 
tract eat u m . 
Row of spines 
from caudal 
sucker of larva. 
Greatly en- 
larged. (Orig- 
inal.) 
larva. Greatly 
enlarged. (Orig- 
inal.) 
DESCRIPTION OF THE LAEVA OF SIMULIUM JENNINGSI. 
The larva of Simulium jenningsi is much smaller than 
that of S. venustum and measures from 3.5 to 4.5 mm. in 
length. The general color is light brownish yellow. The 
head is of a uniform yellow with dark-brown blotches of 
characteristic arrangement on its dorsal surface (PI. IV, 
fig. 3), thus differing from venustum (PI. IV, fig. 4), which 
usually has the pigment in these cells lacking. The an- 
tennae (fig. 7) are slender and 4-segmented, the last seg- 
ment being a short conical process ; the first three seg- 
ments are subequal in this 
species, while the antennae 
of venustum (fig. 8) have 
the second segment longer 
than the first. The labial 
plate (fig. 9) is broader 
than that of venustum 
(fig. 5) the teeth more 
even and equal in size, the 
middle tooth not very 
prominent, and there are 
apparently only two large 
and one small bristle along 
each margin, while venustum has four to five large bristles on each side. 
The mandibles are of the usual type, but rather weak and the teeth some- 
what pale. 
t 
Fig. 8. — Simulium 
venustum. An- 
tenna of larva. 
Greatly en- 
larged. (Orig- 
inal. ) 
Fig. 9. — Simulium jenningsi. La- 
bial plate of larva. Greatly en- 
larged. (Original.) 
