Bramble-bees and Others 



bottom by a feeble grating of silk? The in- 

 sect appears to attach great importance to it, 

 from what I see. As a matter of fact, I watch 

 the careful work of the apex. The grub, 

 whose movements the hole enables me to fol- 

 low, patiently perfects the lower end of the 

 conical channel, polishes it and gives it an 

 exactly circular shape; from time to time, it 

 inserts into the passage its two closed mandi- 

 bles, whose points project a little way outside; 

 then, opening them to a definite radius, like 

 a pair of compasses, it widens the aperture 

 and makes it regular. 



I imagine, without venturing, however, to 

 make a categorical statement, that the per- 

 forated apex is a chimney to admit the air 

 required for breathing. Every pupa breathes 

 in its shell, however compact this may be, 

 even as the unhatched bird breathes inside the 

 egg. The thousands of pores with which the 

 shell is pierced allow the inside moisture to 

 evaporate and the outer air to penetrate as 

 and when needed. The stony caskets of the 

 Bembex- and Stizus-wasps are endowed, not- 

 withstanding their hardness, with similar 

 means of exchange between the vitiated and 

 the pure atmosphere. Can the shells of the 



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