CH. III.] INSECTS WHICH FORM COCOONS. 75 



enemies ; hence nature has instructed the cater- 

 pillar to form a second funnel within the former, 

 formed similarly, but in which the threads are more 

 closely arranged, no aperture being left as in the 

 former. Thus, although the difficulty of entrance 

 from without is increased in consequence of the 

 convexity of the inner funnel, the escape of the 

 moth is scarcely rendered more difficult. Accord- 

 ing to IMeinecken, the pressure of the converging 

 threads of this funnel serves to compress the abdo- 

 men of the moth as it emerges from the cocoon, 

 which forces the fluids to enter the nervures of the 

 wings, and gives them the full expansion. How 

 this is effected, however, we can scarcely conceive ; 

 for as the pressure must be applied against the 

 hind parts of the body while it is forcing itself 

 through the passage, we should have considered 

 that the tluids would have been forced into that part 

 of the body which had not yet undergone that pres- 

 sure, and not into the wings and legs which are at 

 the front of the body, just as in pushing the finger 

 through a tight ring, the blood is forced back into 

 the hand, and not into the tip of the finger. 



It is a remarkable circumstance that some insects 

 are extremely regular in the hours of their appear- 

 ance in the perfect state ; some species, as the silk- 

 worm moth and the Sphinx cenotherce^ being pro- 

 duced at sunrise ; others, as the true hawk moth, 

 at noon ; others, again, as the death's-head moth, in 

 the afternoon ; and lastly, others, as some of the 

 May-flies, only in the evening. 



Hitherto we have only stated instances in which 

 the extrication from the cocoon has been effected 

 by the insect after arriving at the perfect state. 

 The chrysalis itself, in some insects, makes an ap- 

 erture in the cocoon, through which it protrudes a 

 considerable portion of its body, sufficient to allow 

 the moth to disengage itself from the chrysalis 

 without difficulty. The goat moth is an example 



