CHAPTER XXIII 

 ORDER TRICHOPTERA* 



Fig. 316. — Caddice-fly. 



The Caddice-flies 



The members of this order have four wings; these are membranous and 

 usually more or less densely clothed with long, silky hairs. In the more 

 generalized members of the order, the venation of the wings corresponds 

 closely to that of the hypothetical primitive type with but few or no accessory 

 veins; in some of the more specialized members of the order, the venation of 

 the wings is reduced. The mouth-parts of adults, except the palpi, are 

 vestigial. The metamorphosis is complete. 



The caddice-flies are moth-like insects, which 

 are common in the vicinity of streams, ponds, 

 and lakes, and are frequently attracted to lights at 

 night (Fig. 316). The larva? of these insects are the 

 well-known caddice-worms ; these live in the water, 

 and most of them build cases about their bodies. 

 In the adult insect, the body-wall is soft, and is thickly clothed with 

 hairs. The two pairs of wings are membranous and usually more or 

 less clothed with long, silky hair. In a few forms the wings are naked. 

 The hind wings are shorter than the fore wings; but they are usually 

 broader. In one species the female is apterous, and in another the wings 

 of the female are vestigial. When not in use the wings are folded roof- 

 like over the abdomen. 



The eggs of caddice-flies are round or slightly oval in form, 

 are laid either in water or upon objects above 

 water from which the larvae when hatched can 

 find their way into the water. Some species that 

 lay their eggs in water descend below the sur- 

 face in order to glue their eggs to some sub- 

 merged support. So far as is known, most 

 caddice-flies, lay their eggs in a mass enveloped 

 either in a cement, by which the mass is glued 

 to some support, or in a gelatinous covering. In 

 the latter case, the covering absorbs water and 

 thus increases greatly in size. The form of the gelatinous mass and the 

 arrangement of the eggs within it are often characteristic of the species 



(Fig. 317). 



The larvae of caddice-flies, the caddice-worms, found in this country 

 are aquatic and most of them build portable cases in which they live and 

 which they drag about wherever they go projecting only the front end 

 of the body and the legs from the case when they travel. The cases of 

 different species differ greatly in form and in materials vised in their con- 

 * Triehoptcra: trichos (Opi£, rplxos), the hair; ptcron (ttt(poi>), a wing. 



180 



They 



Fin. 317. — Two egg-masse? 

 of caddice-flies: a, Phryganea in- 

 terrupta- b, Trianodes sp. (From 

 Lloyd.) 



