All the species of Termites are not social; but the solitary ones do not, like their congeners, distinguish themselves in architecture. In other respects, their habits are more similar; for they destroy almost every substance, animal and vegetable. The most common of the solitary species must be familiar to all our readers by the name of wood-louse (_Termes pulsatorium_, Linn.; _Atropos lignarius_, Leach)--one of the insects which produces the ticking superstitiously termed the _death-watch_. It is not so large as the common wood-louse, but whiter and more slender, having a red mouth and yellow eyes. It lives in old books, the paper on walls, collections of insects and dried plants, and is extremely agile in its movements, darting, by jerks, into dark corners for the purpose of concealment. It does not like to run straight forward without resting every half-second, as if to listen or look about for its pursuer, and at such resting times it is easily taken. The ticking noise is made by the insect beating against the wood with its head, and it is supposed by some to be peculiar to the female, and to be connected with the laying of her eggs. M. Latreille, however, thinks that the wood-louse is only the grub of the _Psocus abdominalis_, in which case it could not lay eggs; but this opinion is somewhat questionable. Another death-watch is a small beetle (_Anobium tesselatum_). _CHAPTER XVII._ STRUCTURES OF SILK SPUN BY CATERPILLARS, INCLUDING THE SILK-WORM. "Millions of spinning-worms, That in their green shops weave the smooth-hair'd silk." Milton's _Comus_.