V CADDIS-WORMS 251 



sheath, soon dislodges the larva.] On looking at 

 the under side of the head with a lens, we see that 

 the mouth-parts are tolerably like those of caterpillars 

 and other vegetable-feeding larvae. On each side of 

 the mouth is a pair of strong toothed mandibles, well 

 adapted for cutting and shaping the materials of 

 which the sheath is composed, or for dividing the 

 food. Further back is a pair of maxillae with three- 

 jointed palps, while the labium is represented by 

 three pointed triangles, which taper backwards and 

 are armed with teeth along the fore-edge. [The 

 labium is often of simple structure and ends in two 

 minute palps.] 



" The silken lining which comes next to the body 

 of the larvae shows that they can spin, and it is not 

 difficult to sec the thread, either with a lens or with 

 the naked eye, for it is much coarser than that of 

 most caterpillars. I believe that the thread issues 

 from the same place as in caterpillars. I have traced 

 it to the middle of the labium, where the spinneret of 

 a caterpillar is situated. However, I have since sus- 

 pected that the spinneret of the Caddis-worm is not 

 situated here, but further back, in front of the base of 

 the first pair of legs. Here is a soft curved promin- 

 ence directed towards the head, which looks like a 

 spinneret. I have not, however, seen any thread 

 attached to it. [The curved spine between the fore- 

 legs is not the spinneret, but an organ whose function 

 is as yet unknown. The true spinneret is close behind 

 the mouth. Reaumur does not say anything about 

 the silk-gland. As in Chironomus, Simulium, etc., 

 the secretion of the salivary glands forms the silk. 



