HABITS. 



113 



have the same habits ; the latter feeds on birches ; 

 and if we examine these trees in early spring, 

 when all sorts of ichneumon flies are just beginning 

 to wander about in search 

 of prey, we can hardly 

 fail to be struck by the de- 

 ceptive resemblance these 

 hibernacula of the Band- 

 ed Purple bear to the 

 opening buds and curv- 

 ing terminal shoots of the 

 very twig on which they 

 occur [Fig. 99] ; the color 

 of the soft down of the 

 buds and the enveloping 

 silk of the hibernacula is 

 as similar as are their 

 forms ; and this mimetic 

 resemblance is doubtless 

 as effective as it is inter- 

 esting. 



A large number of cat- 

 erpillars attain their full 

 growth and change to 

 chrysalis before winter, 

 passing the cold months in torpid sleep ; but 

 besides the caterpillars of the purples, which 

 hibernate when half grown, there are many others 

 which hibernate at different times of caterpillar 



PIG. 99. Hibernaculnm (a) of 

 Basilarchia Arthemis on a shoot of 

 budding birch as it appears in June 

 in the White Mountains, N. H., to 

 show its resemblance to the buds 

 (6) ; nat. size. 



