40 



GUIDE TO INSECTS. 



Order TRICHOPTEKA. 



The second half of table case 37 contains the Tkichoptera or 

 Caddis-flies. 



These insects are sometimes regarded as a sub-order of the 

 Neuroptera. They have the head free. The antennae are nearly 

 always long and thread-like, tapering to the apex. The mouth parts 

 are small ; the mandibles absent or very rudimentary ; the maxillary 

 palpi very variable, in some genera very large. The thorax is 

 compact ; the prothorax very small. The legs are long and slender 

 with five-jointed tarsi. The front wings are more or less clothed 

 with hair, slightly more leathery than the hind pair, held roof -like 

 when at rest. The hind pair ample and pleated when at rest. 



The larvse live in ponds and streams ; their food consists of 

 vegetable matter. For the most part they live in cases which are 

 built in various ways and of different materials, such as stones, 

 sand, shells, bits of weed, &c. Some of these cases are coiled and 

 being built of fine sand have been mistaken for shells (1478). 



The ordinary Caddis-fly larva (fig. 40) has the 

 Fig. 40. body soft, except the head and thorax that are 



exposed (1461). The first segment of the abdo- 

 men projects on each side, and has on the back a 

 small tubercle which terminates in a sharp hook 

 directed backwards. These projections secure the 

 body in position in the case, whilst at the same 

 time the water can pass freely through the tube ; 

 they also enable the larva to stretch itself out of 

 the tube in search of food. Some of the segments 

 are furnished with floating filaments that serve as 

 gills. At the end of the body there are two 

 strong hooks, which give the larva a firm grip on 

 its case, and enable it to draw back rapidly into 

 the case at the approach of danger. They turn 

 to the pupa within the case, but when ready to 

 turn to the perfect insect, they leave the case, 



Larva of Caddis- sw ™ to ^ e surface of tne water (using the middle 



fly. legs, which are developed like oars for the purpose), 



the skin splits down the back and the fly emerges. 



The perfect insects may be found in trees and herbage 



near water. Some of the very small species so closely resemble 



