MOTHS. 323 



ing, though of different materials, is exactly of the 

 same form, — it 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 Roesel as still more mar- 

 vellous 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 pro- 

 cess 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 re- 

 markable, 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.* 



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 pro- 

 tection from other accidents. The gipsey-moth 

 (Hypogymna dispar), rare in most parts of Britain, 

 is one of these. It selects for its retreat a crack in 

 the bark of the tree upon which it feeds, and over 

 this spins only a few straggling threads. We found 

 last summer (1 829), in the hole of an elm-tree in the 

 Pare at Brussels, a group of half a dozen of these, 

 that did not seem to have spun any covering at all, 

 but trusted to a curtain of moss (Hypna) which 

 margined the entrance. f In a species nearly allied to 

 this, the yellow-tussock (Dasychira pudibmida, Ste- 

 phens), the cocoon, one of which we have now before 

 us, is of a pretty close texture, and interwoven with 

 the long hairs of the caterpillar itself (see figure b, 

 page 20), which it plucks out piece-meal during the 



• J. R. t J- R- 



