THE ANTHRAX FLY 



Now and then there were intervals of rest. At last the 

 hole was made. The pupa slipped into it, but did not 

 pass through entirely. The head and chest appeared be- 

 yond the hole, but the rest of the body remained held in 

 the tunnel. 



The glass cell certainly puzzled my Anthrax. The 

 hole through the pith was wide and irregular : it was a 

 clumsy breach and not a gallery. When made through 

 the Mason-bee's walls it is fairly neat, and exactly of the 

 animal's diameter. For narrowness and evenness in the 

 exit-tunnel are necessary. The pupa always remains 

 half-caught in it, and even pretty securely fixed by the 

 graters on its back. Only the head and chest emerge 

 into the outer air. A fixed support is indispensable, for 

 without it the Anthrax could not issue from her horny 

 sheath, unfurling her great wings and drawing out her 

 slender legs. 



She therefore remains steadily fixed by the graters on 

 her back, in the narrow exit-gallery. All is now ready. 

 The transformation begins. Two slits appear on the 

 head : one along the forehead, and a second, crossing it, 

 dividing the skull in two and extending down the chest. 

 Through this cross-shaped opening the Anthrax Fly 

 suddenly appears. She steadies herself upon her trem- 

 bling legs, dries her wings and takes to flight, leaving her 

 cast skin at the doorway of the gallery. The sad- 



[261] 



