The Humble-Bee Fly. 



429 



these runs the dark digestive s\-stcm. It has a very small, retractile head, armed 

 with bristle-like jaws. Its feet are reduced to six stout bristles. As the cell con- 

 taining the chrysalis was empty, save for the cast grub-skin, it appeared that the 

 fly-grub had eaten the grub of the bee. The chrysalis is much like that of the 

 ghost-moth. On the head are five spines, which represent no corresponding parts 

 in the head of the perfect Insect, and are seen to be special developments to assist 

 the chrysalis to make its way through the clay-stopping with which the mother-bee 

 had sealed up the mouth of its cells. There are numerous bristles and hooks on the 

 various segments of the body, which give the chrysalis leverage to push its head- 



Photo by] 



The Humble-Bee Fly. 



[E. sup, F.L.S. 



A two-winged fly whose form and thick coat of long hairs produces some resemblance to a small humble-bee. U lays its eggs in the 

 vicinity of the nests of solitary bees, where the resiilting grub enters a cell and feeds on the grub of the bee. The fly is shown four 

 times its actual size. 



spines through the clay, and to help it in climbing through thf buirciw, which is 

 from six to ten inches deep. 



It is quite a common thing for moths which >peiul \\\v chrysalis period in 

 wood or earth to have the way made easy for their exit as moths by the 

 caterpillar preparing that wa\' before it becomes a chr3'salis. But in the case of 

 a fly-grub there are no organs that will enable it to do this oftice, and the 

 circumstances of its pupation makes such provision unnecessary. The case 

 of bombylius is quite exceptional, and no other fly-chrysalis appears to be 



