126 OUTLINES OF ENTOMOLOGY. 



molt a number of times, although they differ considerably in form from 

 the larvae. Even the winged insects of a few species molt once or 

 twice, a habit that has no parallel in the life history of the more highly 

 organized forms. The great majority of the species are aquatic, and 

 feed upon insects and other small water animals. In their relation to 

 man they are, with the exception of a few small groups, either neutral 

 or beneficial. The aquatic species form a large part of the food of 

 fishes, and the few terrestrial species mostly prey on small pests of the 

 orchard and garden. 



Following the idea of Prof. Comstock. it will be convenient to 

 separate the Nerve- winged insects into two sections, NEUROPTERA, 

 proper, and PSEUDONEUROPTERA. The insects included in 

 the first section undergo complete metamorphosis, and are therefore 

 ranked by many authors higher than Hemiptera or Orthoptera, although 

 their structural peculiarities would not place them in advance of the 

 latter. The principal families of Neuroptera, proper, are the Oaddice 

 flies (PHRYGANID^E), Ant lions and Lace wings (HEMEROBIAD^E) and 

 the Hellgrammite flies and others (SCIALIDJE). In the Pseudoneu- 

 roptera are grouped a large number of more or less diverse families, 

 including some wingless and degraded parasitic forms. The most 

 interesting and conspicuous species are found in the families of the 

 Dragon-flies (LIBELLULID^E), the May -flies (EPHEMERID^E), the Stone- 

 flies (PERLID^:), and the White ants (TERMITID^E). Here also be- 

 long the little creatures often seen in old or long unopened books, 

 called book-lice (PsooiD^), and the peculiar parasites referred to in a 

 previous chapter, the true Bird-lice (MALOPHAGIDJE). 



The Oaddice fiies closely resemble moths in their general outline? 

 but the wings are of more delicate texture and rather sparsely covered 

 with hairs instead of scales. The antenn* also are like those of moths, 

 being long and thread-like, but there is no coiled tongue, and the other 

 mouth parts are differently developed. The female flies lay their eggs 

 upon water plants, and the aquatic larvae attract much attention on 

 account of the sigular and ingenious little cases which they construct 

 for the protection of their soft bodies. These are made of v silk, and to 

 the outside are attached small pebbles, coarse sand, or bits of sticks 

 or leaves, giving them very peculiar and often beautiful forms. Some 

 species make their cases entirely of silk, and of a very elongated cone 

 shape. The thoracic legs are long and strong, and when moving from 

 place to place, the case is dragged along over the* hinder end of the 

 body, but when resting or molting the larva retires within it and closes 

 the opening by a little door or grating, which admits the water neces- 

 sary to respiration, but excludes enemies. These case-bearing larvae 

 may be found along the shores of lakes and in the beds of shallow 



