60 NATURAL HISTORY. [cH. Ill 



Reaumur has also narrated the proceedings of a 

 small hairy caterpillar, which feeds upon lichens, 

 and which appears to us to be that of the muslin 

 moth {Nurj^aria mundana), which Schaffer has figured 

 and described at great length under the name of 

 the steinmoosraupe — the stone-moss caterpillar. 

 These caterpillars form their cocoons about the 7th 

 or 8th of July, and, at first sight, they may easily 

 be mistakeu for the caterpillars themselves ; the 

 cocoons are found upon walls or on flat bits of 

 stone, and in forming them the caterpillar pulls oflf 

 its hairs and plants them in an upright position 

 round its body, side by side, like the pales of a pali- 

 sade, in an oval ring, in the middle of which it is 

 itself stationed ; within this enclosure it spins a 

 slender web, which scarcely conceals the chrysalis. 

 This tissue supports the hairs, which are forced to 

 bend over it at the top by silken threads, so as to 

 form a kind of roof. The perfect insect appeared 

 about the 25th of July. 



It has been considered by the author of the " In- 

 sect Transformations" (p. 180), to be one of the 

 most striking instances of instinctive foresight, that 

 the caterpillars which build cocoons of a substantial 

 structure are destined to remain much longer in the 

 chrysalis trance than those which spin merely a 

 flimsy web of silk, the latter, for the most part, be- 

 ing stated to undergo their final transformation in a 

 few weeks, while the former continue entranced 

 the larger portion of the year, appearing in the per- 

 fect state the summer after their architectural la- 

 bours have been completed. As we cannot but 

 acknowledge that the view of nature exhibited by 

 this thjory is an interesting one, we regret that we 

 are under the necessity of stating that it is unsup- 

 ported by facts ; for instance, there are many but- 

 terflies which pass the winter in the pupa state, and 

 yet their cocoons are destitute of any covering at 

 all. Again, some of the most robust cocoons are 



