180 TRICHOPTERA. 



become colored. The larvae live in cases somewhat 

 after the manner of the hermit crab, but unlike that 

 unprincipled animal they set themselves honorably at 

 work and make an artificial covering or case by fast- 

 ening small stones and sticks together, as seen in Fig. 

 126. 



The eyes are small, and here there is an exception 

 to the general statement of the relation of these parts, 

 since the usual compensation in other sense organs is 

 not provided, the antennae being wanting. The man- 

 dibles are strong because they perform the double 

 work of mastication and locomotion. If the caddis- 

 worm is placed on the hand, it fastens its mandibles 

 in the cuticle of the skin and pulls itself and its case 

 along, oftentimes with such strong, quick motions that 

 it turns half a somersault, coming down upon its back. 



The first abdominal ring, or the one behind the 

 metathorax, belongs apparently with the thorax, and 

 bears three round, blunt organs (not clearly shown 

 in the drawing), one on either side, and one in the 

 middle of the dorsal surface. These enlarge and 

 contract as the animal moves. The rings of the 

 abdomen, with the exception of the first, bear on 

 both sides rows of white filaments which are respira- 

 tory organs. These come off from either side of the 

 sutures that separate the rings, and on the last ring 

 there is a pair of jointed appendages with stout, horny 

 hooks at their ends, the points of which are directed 

 forward. It is by means of these hooks that the animal 

 is held securely in its case when attempts are made to 

 pull it out. When the larva is ready to change into 

 the pupa (Fig. 127), it closes the tube and remains 



