154 THE COMMON HOUSE-FLY. 



steps. About an hour before the}^ die, all intentional mo- 

 tion ceases, and the fly fixes its proboscis firmly to the ob- 

 ject it happens to have settled upon, only the legs spas- 

 modically contract and extend in a very unsymmetrical 

 way, as shown in the illustrations, figs. 127 and 128. The 

 abdomen gradually swells and shows on its underside a 

 v^'hitish color; the upper surface of the insect, however, does 

 not change at all, and no trace is as yet visible of the white 

 rings between the segments, nor is any white dust to be 

 seen. Gradually all motion ceases, and the animal is dead. 

 After death the abdomen still swells, and about eight hours 

 afterward it is so much distended that the segments are 

 pulled apart, and the fine connecting skin between them be- 

 comes visible, and here a white substance is gradually 

 pushed out from the interior, so that eventually three white 

 and parallel rings or belts are formed. The first trace of 

 loose dust becomes now visible under the insect. The fly re- 

 mains unaltered in this condition for several days, only 

 these belts become more prominent, and frequently a white 

 ring is also visible between head and thorax. The dust 

 around the dead fly becomes denser, the corpse eventually 

 dries up, the white belts disappear, and the body shrinks so 

 that the fly looks like a living one, though wings and legs 

 are covered with dust (fig. 128, plate VH). Thus far all the 

 symptoms could be followed with the naked eye, but the 

 microscope alone can give us an explanation of the whole 

 process. 



"Being afraid that, bj^ this time, you will be thoroughly 

 sick of the EnipuKd, I will not inflict upOn 3^our patience the 

 history of the microscopic influenza, another disease that at- 

 tacks our domesticated fly. It goes hy the name of Isaria, 

 was first discovered by Meigen, and has but one good point 

 about it — it kills flies. 



"To wind up this alread3^ lengthy discourse upon diseases 

 of flies, let me only mention some other enemies — besides 

 yourselves — of this troublesome intruder to an afternoon's 

 snooze, knowing that it will please you to hear that the life 

 of the fly is far from being an eternal round of revelry and 

 pleasure, and that it is troubled in more than one way. 



