154 THE COMMON HOUSE-FLY. 
steps. About an hour before they 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 
whitish 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 VII). 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, by this time, you will be thoroughly 
sick of the Empusa, I will not inflict upon your patience the 
history of the microscopic influenza, another disease that at- 
tacks our domesticated fly. It goes by the name of Lsaria, 
was first discovered by Meigen, and has but one good point 
about it—it kills flies, 
‘Lo wind up this already 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. 
