164 



NATURAL HISTORY OF ARTHROPODS. 



The caddis flies are very common, flying about damp places and brooks, sometimes 

 in swarms ; they are usually dull-colored, but a few species are beautifully colored ; 

 the species of Setodes, for example, are usually snow-white. 



FIG. 237. Limnophilus rhombicus, caddis fly; , case; 6, larva; c, pupa; d and e, adult. 



The transformations of the caddis flies are interesting. The eggs are deposited in 

 a double gelatinous green mass, which is attached to the surface of some aquatic plant. 

 Westwood says that the female of Phryganea grandis has been observed to creep down 

 the stems of aquatic plants under the water, very nearly a foot deep, for the purpose 

 of laying its eggs. On the other hand, according to McLachlan, the egg-masses, prob- 

 ably of Halesus, are sometimes deposited on leaves of trees far from water. 



With one known exception, which lives in moss on land, the larvae 

 of all the caddis flies live at the bottom of ponds and streams. They 

 are all protected by some sort of a case ; hence their name, case- 

 worms. There is no end to the variety of form in these cases, and 

 the material of which they are constructed. The accompanying illus- 

 trations will serve to represent a few characteristic forms. 



Certain caddis worms roll up leaves, cutting them properly so as to 

 roll up with ease, or they sew them together by spinning silken threads 

 from their mouth, attaching to their case large irregular bits of leaves ; 

 others attach deserted or " dead " snail shells, or bits of gravel, coarse 

 or very fine, or sand ; and others, living in mill streams, cover their 

 cases with coarse sawdust. The cases are usually 

 straight, sometimes curved like a horn, while that of 

 Helicopsyche is wound in a spiral like a snail shell. 

 More is actually known about the case-worms of southern Brazil than 

 those of North America, owing to the observations of Fritz Mtiller, who 

 resides in that country, but as there are undoubtedly many similar species 

 in North America we will refer at some lenerth to the different Brazilian 



O 



forms. Of a genus (Tetracentron) allied to Z/eptocerus, and whose 

 imago is remarkable for having gills, one species uses hollow sticks for 

 its case. Of certain forms allied to Rhyacopldlus one lives, almost 

 without any case, between the tangled stems of water-plants ; the an- 

 terior legs of the larva are armed with curious, powerful forceps ; the cocoon of the 

 pupa is not protected by a regular case. Smaller species of an allied genus build 



Fm. 238. Larva and 

 case of Limnophi- 

 lus subpunctulatus. 



FlOf. 239. Larva 

 of Leptocerus. 



