TRICHOPTERA. 147 



leafy or lichenous tent of other species of moths. The 

 aquatic habit of the Phryganea larva is alone, however, 

 sufficient to distinguish the insect in this state, while the 

 perfect fly may be distinguished by the hairy covering of 

 the wings, the wings of moths being covered with dust 

 or minute scales. 



The other characters easy to observe, and which dis- 

 tinguish these orders, are the ocelli or simple eyes, 

 which in Lepidoptera are two or none, in Trichoptera 

 three or none, and the organs of the mouth which, though 

 smaller in the case-bearing moths than in other species, 

 are yet fully developed (according to the Lepidoptera 

 form as described in Chapter ii.), while the mouth of 

 the Caddis-fly is almost undeveloped, and is of a totally 

 different type*. 



These insects vary in size, some being small, others 

 about an inch in length. They run with some activity, 

 but the flight of at least the larger species is uncouth 

 and apparently unenjoying. They frequently enter our 

 rooms at night attracted by the light, and make their 

 presence known by the rustling paper-like sound with 

 which they strike against the ceiling. 



Altogether the flies themselves are among the least 

 interesting of insects, unless indeed they acquire interest 

 from the great difficulties which attend their investiga- 

 tion ; but as in some other cases the larvaB quite make up 

 any deficiencies of this kind in the perfect insect, and 

 excepting those of Hymenoptera the dwellings of 

 the little Caddis-worms are excelled by none in 

 beauty. 



They vary much both in material and in the mode of 

 construction. Phryganea Grandis, a large and common 

 species, forms an uncouth enough looking case of large, 



L 2 



