564 



AN INTRODUCTION TO ENTOMOLOGY 



"Several species of the genus Polycentropus live in still or slowly 

 flowing water with sandy or muck bottoms. These larvae spin sub- 

 terranean tubes of silk 

 which sometimes reach 

 lo centimeters in length. 

 Often the tubes have one 

 or more branches, and al- 

 ways they contain a bulb- 

 ous swelling near the 

 middle in which the larva 

 probably rests, and in 

 which pupation takes 

 place. In natural posi- 

 tion the tubes are be- 

 neath the ground, except 

 about half an inch which 

 projects upward into the 

 water." (Lloyd.) 



Two quite different larv'al tubes of members of this family are 

 described and figured by Miss Noyes. One of these is represented 

 in Figure 694. This tube is found on the under side of stones, and 

 is fastened along its entire length. "It is 21 mm. long and 5.5 mm. 

 wide, with an expanded opening at either end. Connected with each 

 opening and along either side is a mass of tangled, silken threads, 

 about 20 mm. square and loosely attached to the stone. This tangled 

 mass may float partially over the tube and so obscure it." 



"I have never observed the larvae feeding, but do not doubt that 

 Mayfly nymphs and chironomid larvae become entangled in the 

 meshes as they crawl about over the stones, for remains of these 

 forms are abundant in the stomach contents." (Noyes.) 



Fig. 694. — Dwelling of Polycentropus sp. (From 



Noyes.) 



Family PSYCHOMYID^ 



The larvae are campodeiform. There is no account of the life- 

 history of any American species published. The European species 

 do not make portable cases; but the larvae live on stones in long, 

 loosely-spun galleries of silk and sand grains. They are found mostly 

 in swift water, but also inhabit ponds and lakes. 



Family PHRYGANEID^ 



The larvae are caterpillar-like, and usually live in standing water 

 in which plants are growing, or in slowly moving streams of spring 

 water. They make portable cases which are very regular in form. 

 As these larvcE live in quiet water, they can be fed and reared in aquaria 

 where their habits can be easily observed. The most extended account 

 of the immature stages of these insects is that of Lloyd ('21), from 



