226 STATES OF INSECTS. 



hair and so little silk enter into the composition of their 

 cocoons, that on the first inspection they would be pro- 

 nounced wholly composed of it a ; others, thickening the 

 interior of their cocoon with hair, line the whole with a 

 viscid matter like varnish b . 



The larvee of some saw-flies (Tenthredo L.) are re- 

 markable for inclosing themselves in a double cocoon, in 

 which the inner is not, as in the silk-worm &c, connected 

 with the outer, but perfectly distinct from it. Some spe- 

 cies, as T. Rosce {Cryptus Jur.), which have but a small 

 stock of silk, compose the outer cocoon of thick silken 

 cords crossing at right angles, and forming an oval net; 

 which at the same time that it protects them effectually 

 from the ants, which are always ready to attack them, de- 

 mands much less silk than a covering of a closer texture. 

 But the tender nymph itself requires to be inclosed in a 

 case of a softer and more delicate substance ; and accord- 

 ingly the inner cocoon is composed of fine silk, woven 

 so closely that the threads are scarcely perceptible under 

 a microscope c . Reaumur mentions a hymenopterous 

 larva belonging to Latreille's Fossores (Sphex L.) which 

 thickened its cocoon with the legs, wings, and other relics 

 of the flies which it had devoured d : trophies — like the 

 drinking- cups of some savages, made of the skulls of their 

 enemies, or the skull -pyramid near Ispahan — of its 

 powers of devastation. 



It is a general rule, that those larvae which spin co- 

 coons, never in ordinary circumstances become pupae 

 without having thus inclosed themselves. An exception, 

 however, is met with in the larva of a species of ant no- 



a Bonnet ii. 297. b Ibid. ix. 181. 



c Reaum. v. 102. <> Ibid. iy. 269. 



