290 INSECTS AT HOME. 



ordinary cow's horn. lu fact, the materials, and o)nse.iuently 

 the forms, of these remarka})le habitations are so various that 

 it is impossible to do more than briefly describe the leading- 

 varieties. 



All the habitations which liave just been mentioned are 

 movable, and are carried about by the larva, just as the Hermit 

 Crab carries its shell-house with it. There are, however. 

 Caddis-cases which are fixed to stones, and which cannot be 

 moved. Such, for example, are the habitations of Hydro- 

 Ij^yche senex and Hydropsyclte maculicornis^ the former of 

 which makes a house that is shaped very much like a leech 

 when at rest, and is fixed by the whole of its under side to the 

 stone. The habitation of the latter, however, is quite worm- 

 like in shape, and often considerably curved. 



In consequence of the differing form of these habitations, it 

 follows that there must be a corresponding difference in the 

 structure of the inhabitants. All the Caddis larv£E hold them- 

 selves within their cases by means of claspers at the end of the 

 body, and very firmly they hold, as anyone can tell who has 

 ejected them from their habitations. But these claspers are 

 modified in their construction according to the kind of habita- 

 tion. Those larvae which dwell in movable tubes never leave 

 them, but crawl at liberty from one spot to another in search of 

 food. They have really wonderful powers of adhesion, and can 

 climb smooth and hard surfaces with the greatest ease. There 

 are now before me some larvse of Sericostoma which have 

 crawled up the sides of a glass vessel, one or two of them 

 having even raised themselves partially above the surface of the 

 water. In all these species the claspers are short, so that they 

 only permit the head and leg-bearing segments of the body to 

 protrude beyond the mouth of the tube. But in the species 

 which live in fixed tubes the claspers are placed at the ends of 

 two long footstalks, so that the larva can thrust itself far out of 

 its tube, and thus obtain a wide range wherein to procure food. 

 Some of these creatures feed upon small aquatic larvse, but the 

 food of the greater part seems to be mostly vegetable, thougli 

 all the species appear to vary their diet occasionally with 

 animal svibstances. 



^\'hatever may be the species, and whatever the material of 

 their cases, the various portions of which the habitations are 



