The Mason-bees 



apartments with silk, we see the Stilbum take 

 her stand on the inviolable citadel. No doubt 

 some imperceptible cranny, some defect in the 

 cement, allows her to insert her ovipositor, 

 which shoots out like a probe. At any rate, 

 about the end of the following May, the 

 Eumenes' chamber contains a cocoon which 

 again is shaped like a thimble. From this 

 cocoon comes a Stilbum calens. There is 

 nothing left of the Eumenes' grub: the 

 Golden Wasp has gorged herself upon it. 



Flies play no small part in this brigandage. 

 Nor are they the least to be dreaded, weak- 

 lings though they be, sometimes so feeble that 

 the collector dare not take them in his fingers 

 for fear of crushing them. There are some 

 clad in velvet so extraordinarily delicate that 

 the least touch rubs it off. They are fluffs of 

 down almost as frail, in their soft elegance, 

 as the crystalline edifice of a snowflake before 

 it touches ground. They are called Bombylii. 



With this fragility of structure is combined 

 an incomparable power of flight. See this 

 orre, hovering motionless two feet above the 

 ground. Her wings vibrate so rapidly that 

 they appear to be in repose. The insect looks 

 as though it were hung at one point in space 

 196 



