THE ANTHRAX FLY 183 



segments, including its tiny head, which bristles in front with 

 short, stiff hairs. There are four other pairs of bristles on 

 the lower surface, and with the help of these it walks. 



For a fortnight the feeble grub remains in this condition, 

 without growing, and apparently without eating. Indeed, 

 what could it eat ? In the cocoon there is nothing but the 

 larva of the Mason-bee, and the worm cannot eat this before 

 it has the sucker or mouth that comes with the second form. 

 Nevertheless, as I said before, though it does not eat it is far 

 from idle. It explores its future dish, and runs all over the 

 neighbourhood. 



Now, there is a very good reason for this long fast. In the 

 natural state of the Anthrax-grub it is necessary. The egg is 

 laid by the mother on the surface of the nest, at a distance 

 from the Bee's larva, which is protected by a thick rampart. 

 It is the business of the new-born grub to make its way to its 

 provisions, not by violence, of which it is incapable, but by 

 patiently slipping through a maze of cracks. It is a very 

 difficult task, even for this slender worm, for the Bee's masonry 

 is exceedingly compact. There are no chinks due to bad 

 building, no cracks due to the weather. I see but one weak 

 point, and that only in a few nests : it is the line where the 

 dome joins the surface of the stone. This weakness so seldom 

 occurs that I believe the Anthrax-grub is able to find an 

 entrance at any spot on the dome of the Bee's nest. 



The grub is extremely weak, and has nothing but invin- 

 cible patience. How long it takes to work its way through 

 the masonry I cannot say. The work is so laborious and the 

 worker so feeble ! In some cases I believe it may be months 

 before the slow journey is accomplished. So it is very fortu- 

 nate, you see, that this first form of the Anthrax, which exists 

 only in order to pierce the walls of the Bees' nest, should be 

 able to live without food. 



At last I saw my young worms shrink, and rid themselves 

 of their outer skin. They then appeared as the grub I knew 

 and was so anxiously expecting, the grub of the Anthrax, the 



