HABITATIONS OF INSECTS. 299 



incommoded by the long hairs which surround them as we are by walking 

 amongst high grass ; and accordingly, marching scythe in hand, with their 

 teeth they cut out a smooth road, from time to time reposing themselves, 

 and anchoring their little case with small silken cables. 



If, as I hope, you are induced to investigate the manners of these 

 insects, you have but to leave an old coat for a few months undisturbed in 

 a dark closet, and you may be pretty certain of meeting with an abundant 

 colony. 



Not merely wool or hair, but another substance analogous to one 

 employed in our dress, is adopted for their clothing by other insects. The 

 larva of a fly which lives on the seeds of willows makes itself a very 

 beautiful case of their cottony down, not only impervious to wet and cold, 

 but serving, if accidentally blown into the water, which, from the situation 

 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 Pyryganece L., a tribe of four- 

 winged insects, which an ordinary observer would call moths, but which 

 are even of a distinct order (Trichoptera^ , 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 observe at the bottom little oblong moving masses, resembling 

 pieces of straw, wood, or even stone. These are the larvae 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 inclosed, 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 Sahella^, 

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

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

 Leptocenis himaculatus, which is less artificially constructed of a mixture 

 of mud and sand, is pyriform, and has its end curiously stopped by a plate 

 formed of grains of sand, with a central aperture.^ Other species con- 

 struct houses which may be called alive, forming them of the shells of 

 various aquatic snails of different kinds and sizes, even while inhabited, 



» Reaum. iii. 130. « Keautn. iii. 156—159. 



^ Sowerby's Nat. Miscell. No. ix. t. 51. * De Geer, ii. 564. 



