268 



NATUBAL HISTOEY. 



upon a pane of glass, and here the breadth and firmness 

 of the attachment of the base of each footstalk were very 

 manifest, seen through a small microscope. 



459. There is an aberrant family of this section called 

 Caddice-flies, remarkable for the covering of hair with 

 which both their bodies and wings are beset. The hab- 

 its of their larvae are very interesting. They are aquatic, 

 and live in cylindrical cases open at each en'd. To these 

 cases they attach various substances, such as bits of 

 wood, weeds, pebbles, shells, etc. In Fig. 209 are repre- 

 sented several of 

 these tubular houses 

 with various things 

 attached to them. 

 The different spe- 

 cies, of which there 

 are many, seem to 

 have their individ- 

 ual preferences in 

 relation to the sub- 

 stances which they 

 employ ; but they 

 readily disregard 

 these preferences when there is a lack of those materials 

 which they usually prefer. They never willingly leave 

 their cases, but only thrust the head and a portion of the 

 body out in search of their food. When about to pass 

 into the torpid pupa state, they fasten their tubular houses 

 to something in the water, and then close the two ends 

 with a kind of silken grating which allows the water to 

 pass freely through it. When they are to assume the 

 imago form, they make a hole in the grating with a pair 

 of hooked jaws which they now have. They are now 

 good swimmers, using chiefly their hind legs for this pur- 

 pose. Coming to the surface of the water, and perhaps 

 climbing up some plant, the skin of the swimmer gapes 

 open, and out flies an insect about double the size of that 



Fig. 209. Caddice-fly. 



