Entomology of the Illinois River. 201 



latter. The larvae were first noticed there on March 17, 

 1895, their dirty brown color rendering them difficult of 

 detection. They were then about half to two thirds grown. 

 More were taken on the 28th, from which a pupa [Fig. 

 31 J was obtained April 13. Two days later an exam- 

 ination of the original situation revealed an abundance 

 of mature larvae and several pupae, which were placed 

 in breeding-cages. April 20 was warmer than usual, and 

 the majority of the larvae then pupated, while the pupae 

 all transformed into males of the above species, agreeingia 

 every detail with Osten-Sacken's description and figure 

 in his monograph of the Brevipalpi. The first pupa 

 mentioned had already transformed on the 18th. During 

 the next few days most of the pupee allowed to remain 

 reached the final stage. A siug'e pupa had been pre- 

 viously found in 1894, Aug. 16, at Station B. The 

 imagos are said by Osten-Sacken to be common from 

 early spring through the greater part of the summer. 



It was ascertained by dissection that the larval food was 

 very similar to that of the Bittacomorpha, the intestine 

 being packed with a cylindrical mass consisting largely 

 of fragments of dead vegetation, with a great profusion 

 and variety of diatoms and a quantity of peculiar ta- 

 pering filaments which seem to be minute algae. 



An interesting feature of the species is the high devel- 

 opment of delicate fringes about the respiratory openings 

 [Fig. 30]. As seen in the water, the larva apparently 

 has a tail-like appendage on the last segment ; but the 

 moment this is brought to the surface, it opens and 

 expands, forming a broad fringe about the spiracular 

 disks. It can then be seen that the latter are protected 

 by four narrow black lamellate appendages, a shorter 

 one on each side and a pair of long ones just below, tht ir 

 edges closely fringed with long fine hair, very lono- 

 toward their tips, the fringe being continued across the 

 intervening spaces, so as to completely enclose the stig- 



