TRANSFORMATIONS OF BUFFALO GNATS. 



maining segments are densely covered with minute pubescence inter- 

 spersed thickly with stronger hairs. The antennae 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 

 Tabaniclse. 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. — Simuliiim 

 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.) 



