US 



INTRODUCTION TO ZOOLOGT. 



existence ia the water. Mr. Hyndman, of Belfast, noticed, 

 some years ago, the proceedings of the female in one of the 

 ponds in the Botanic Garden, near that town, and favoured 

 us with the following note : — r" I first observed the Phryganea 

 on the leaf of an aquatic plant, from which it crept down 

 along the stem under the water, very nearly a foot deep; it 

 appeared then to have been disturbed by some stickle-backs, 

 which approached and seemed inclined to attack it, and swam 

 vigorously and rapidly beneath the water, over to some other 

 plants. I there took the insect up, and found a large bundle 

 of eggs, of a green colour, closely enveloped in a strong jelly- 

 like substance, attached to the extremity of its abdomen." 



The larvae of these flies, well known under the name of 

 Case-worms, or Caddis- worms (Fig. 102), are to be found in 



Fig. 102. — Caddis-worms. 



every running stream, and almost in every ditch. Their 

 habitations are extremely singular, and differ considerably, 

 both in the materials employed and in their external con- 

 figm-ation. Some are formed of numerous little pieces of grass 

 and stems of aquatic plants cut into suitable lengths and placed 

 crossways, forming a rude polygonal figure ; others are con- 

 stnicted of bits of stick, or grains of sand and gravel, cemented 

 together; and others, again, are composed of fi'esh- water 

 shells, each containing its own proper inhabitant, "a covering," 

 as Kirby and Spence remark, " as singular as if a savage, 

 instead of clothing himself with squirrel-skins, should sew 

 together into a coat the animals themselves." But, whatever 

 may be the material employed, the little builders contrive to 

 make them of nearly the same specific gravity as the water, 

 so as to bo carried without labour. When about to assume 

 the pupa state, they construct a kind of grating at each 

 extremity of the case, and thus provide, at the same time, for 

 respiration and defence. 



