344: Insect Architecture. 



fluids into the nervures of the wings ; for when he took the 

 chrysalis previously out of the cocoon, the wings of the moth 

 never expanded properly.* Had he been much conversant 

 with breeding insects, he would rather, we think, have imputed 

 this to some injury which the chrysalis had received. We 

 have witnessed the shrivelling of the wings which he alludes 

 to, in many instances, and not unfrequently in butterflies 

 which spin no cocoon. The shrivelling, indeed, frequently 

 arises from the want of a sufficient supply of food to the 

 caterpillar in its last stage, occasioning a deficiency in the 

 fluids. 



The elasticity of the cocoon is not peculiar to the emperor- 

 moth. A much smaller insect, the green cream-border-moth 

 (Tortrix clilorana) before mentioned (page 190), for its 

 ingenuity in bundling up the expanding leaves of the willow, 

 also spins an elastic shroud for its chrysalis, of the singular 

 shape of a boat with the keel uppermost. Like the cater- 

 pillar of Pyralis strigulalis (page 217), whose building, 

 though of different materials, is exactly of the same form, ' 

 its first spins two approximating walls of whitish silk, of the 

 form required, and when these are completed, it draws them 

 forcibly together with elastic threads, so placed as to retain 

 them closely shut. The passage of the moth out of this 

 cocoon might have struck Eoesel as still more marvellous 

 than that of his emperor, in which there was at least a small 

 opening ; while in the boat cocoon there is none. We have 

 now before us two of these, which we watched the caterpillars 

 through the process of building, in the summer of 1828, and 

 from one only a moth issued the other, as often happens, 

 having died in the chrysalis. But what is most remarkable, 

 it is impossible by the naked eye to tell which of these two 

 has been opened by the moth, so neatly has the joining been 

 finished. (J. B.) 



Some species of moths spin a very slight silken tissue for 

 their cocoons, being apparently intended more to retain 

 them from falling than to afford protection from other acci- 

 dents. The gipsy-moth (Hypogymna dispar), rare in most 

 * Memecken, quoted by Kirby and Spence, iii. 280. 



