98 INTRODUCTION. 



closely gummed, that had both ends been similarly 

 closed, its egress would have been impracticable ; 

 it finds, however, no difficulty in forcing its way 

 through the aperture of a sort of reversed funnel, 

 formed of converging threads that readily yield to 

 pressure from within. But an objection will here 

 probably strike you. You will ask, Is not this 

 facility of egress purchased at too dear a rate? 

 Must not a chrysalis, in an open cocoon, be exposed 

 to the attacks of those ichneumons of which you 

 have said so much, and of numerous other enemies, 

 which will find admittance through this vaunted 

 door ? Our caterpillar would seem to have foreseen 

 your dilemma; at least, under heavenly guidance, 

 she has guarded against the danger as effectually as if 

 she had. If you cut open the cocoon longitudinally, 

 you will see that within the exterior funnel-shaped 

 end, at some distance, she has framed a second funnel, 

 composed of a similar circular series of stiff threads, 

 which, proceeding from the sides of the cocoon, con- 

 verge also to a point, and form a sort of cone exactly 

 like the closed peristome of a moss; or, to use a 

 more humble though not less apt illustration, like 

 the wires of certain mouse-traps. In this dome not 

 the slightest opening is left, and from its arched 

 structure, it is impenetrable to the most violent 

 efforts of any marauders from without; whilst it 

 yields to the slightest pressure from within, and 

 allows the egress of the moth with the utmost 

 facility. When she has passed through it, tne 

 elastic threads resume their former position, and 



