TRANSFORMATIONS OF BUFFALO GNATS. 
maining segments are densely covered with minute pubescence inter- 
spersed thickly with stronger hairs. The antennse of the male are 
similar in structure to those of the female, except that they are 
more slender and have the third segment much 
longer, twice the length of any of the succeeding 
segments, and the tenth segment usually the same 
length as the one immediately preceding it. (Figs. 
1 and 2.) 
The mouth parts are modified in both sexes into 
a piercing beak, somewhat similar to that of the 
Tabanida?. In the male the organs have become 
greatly reduced both in strength and armature, so 
that they are apparently unable to pierce the skin 
of vertebrates. 
DESCRIPTIONS OF INTERNAL ANATOMY. 
Digestive System. 
PI. I, fig. 2. 
Fig. 1. — Simulium 
venustum. An- 
tenna of adult 
female. Greatly 
enlarged. (Orig- 
inal.) 
The following is a description of the digestive 
organs of Simulium venustum. The diverticulum 
of the oesophagus, or sucking stomach (v e), which is sometimes 
described as the midintestine or stomach, and whose function seems 
to be primarily that of a reservoir for blood, is a large membranous 
bag capable of great distention. At its caudal end it narrows to the 
constriction known as the pyloric valve (jp). This 
is the place of attachment of the Malpighian tubes. 
The Malpighian tubes (m, m), which are greatly 
developed in this insect, are four in number and are 
constricted at intervals, with corresponding lobular 
enlargements. They extend from the base of the 
diverticulum to its cephalic end, turning again 
caudad, and ending, as far as can be ascertained, in 
a small blind nodule. They are opaque white in 
specimens which have not fed, or specimens dissected 
on emergence, but show remarkable changes in color 
at various periods after engorgement. Sometimes 
they are pink, sometimes rather brownish, and in 
specimens which have engorged and lived for 40 
hours they become checkered brown with trans- 
parent intervals. 
The ileum (i), which is situated immediately below the pyloric 
valve, is an elongate, rounded intestine, somewhat curved when in 
its natural position. The substance which it contains is invariably 
more solid than that found in the diverticulum, large granules being 
frequently present. 
Fig. 2. — Simulium 
venustum. An- 
tenna of adult 
male. Greatly 
enlarged. (Orig- 
inal.) 
