364 THE NATURAL HISTORY 



in masses to some portion of a plant at some depth 

 in the water, and no sooner are the larvae hatched, 

 than they set about the construction of their portable 

 habitations. These are simply silken tubes open at 

 both ends, and so accurately ballasted with a casing 

 of various materials, that they do not impede the free 

 progress through the water of the larvae within them, 

 being neither too buoyant for the bottom-feeding 

 species, nor too heavy for those that seek their food 

 nearer the surface. The head and legs of each larva 

 project from what may be termed the mouth of its 

 case, while the remaining part of the body is retained 

 in it by means of a pair of articulated hooks at trie 

 extremity of the abdomen, so that it is difficult to 

 eject the tenant from its tubular dwelling, the more so 

 as the slightest alarm causes it to disappear wholly 

 within it, as a snail retires within its shell. When, 

 however, by one who knows how to set about it, a 

 larva is extracted from its case unharmed, it is found 

 to be a rather long tapering fleshy grub, with dark 

 head and six comparatively short legs, in this form 

 the angler finds it a very efficient bait for several 

 species of fish. Its food is partly animal, partly 

 vegetable, but in the perfect insect the total absence 

 of masticating or suctorial organs, would lead to the 

 inference that at this closing period of its career, it is 

 incapable of taking any food whatever. 



A complete collection of the cases of Caddis-worms, 

 must be a singularly interesting one, some of the 

 species will be seen to be botanists, others concholo- 

 gists, and others again mineralogists, thus presenting 

 in their economy a striking analogy to Onustus, an 

 exotic genus of marine molluscs, which incorporate 

 within the substance of their own shells, as fast as 

 they secrete them, fragments of minerals, shells and 

 other materials. One specimen in our own collection 

 (Onustus conchy liophorus), when looked at in its natural 

 position, has the appearance of a small conical heap 



