396 



HABITATIONS OF INSECTS. 



of these trees, frequently happens, as a buoyant little barge 

 which is wafted safely to the shore. ^ 



The habitations which we have hitherto been considering 

 are formed by larvae that live on land; but others equally 

 remarkable are constructed by aquatic species, the larvae of 

 the various Phryganem L., a tribe of four- winged insects, 

 which an ordinary observer would call moths, but which are 

 even of a distinct order ( Triclioptera), not having their wings 

 covered by the scales which adorn the lepidopterous race. If 

 you are desirous of examining the insects to which I am 

 alluding, you have only to place yourself by the side of a 

 clear and shallow pool of water, and you cannot fail to ob- 

 serve at the bottom little oblong moving masses, resembling 

 pieces of straw, wood, or even stone. These are the larvse in 

 question, well known to fishermen by the title of Caddis- 

 worms, and which, if you take them out of the water, you 

 will observe to inhabit cases of a very singular conformation. 

 Of the larva itself, which somewhat resembles the caterpillars 

 of many Lepidoptera, nothing is to be seen but the head and 

 six legs, by means of which it moves itself in the water, and 

 drags after it the case in which the rest of the body is in- 

 closed, and into which on any alarm it wholly retires. The 

 construction of these habitations is very various. Some 

 select four or five pieces of the leaves of grass, which they 

 glue together into a shapely polygonal case ; others employ 

 portions of the stems of rushes, placed side by side, so as to 

 form an elegant fluted cylinder ; some arrange round them 

 pieces of leaves like a spirally-rolled ribbon ; others inclose 

 themselves in a mass of the leaves of any aquatic plants 

 united without regularity ; and others again form their abode 

 of minute pieces of wood either fresh or decayed.^ One, 

 like the SabellcE^, forms a horn-shaped case composed of 

 grains of sand, so equal in size, and so nicely and regularly 

 gummed together, the sides throughout being of the thick- 

 ness of one grain only, that the first time I viewed it I could 

 scarcely persuade myself it could be the work of an insect. 



1 Reaum. iii. 130. 2 Reaum. iii. 156 — 159. 



^ Sowerby's Nat. Misctll. No. ix. t. 51. 



