366 
ANIMALS OF EGA. 
Chap. Y. 
which have a very long ovipositor, and which belongs 
to the genus Stylogaster (family Conopsidse). These 
swarms hover with rapidly-vibrating wings, at a height 
of a foot or less from the soil over which the Ecitons 
are moving, and occasionally one of the flies darts with 
great quickness towards the ground. I found they 
were not occupied in transfixing ants, although they 
have a long needle-shaped proboscis, which suggests 
that conclusion, but most probably in depositing their 
eggs in the soft bodies of insects, which the ants were 
driving away from their hiding-places. These eggs 
would hatch after the ants had placed their booty in 
their hive as food for their young. If this supposition be 
correct, the Stylogaster would offer a case of parasitism 
of quite a novel kind. Flies of the genus Tachinus 
exhibit a similar instinct, for they lie in wait near the 
entrances to bees' nests, and slip their eggs into the food 
which the deluded bees are in the act of conveying for 
their young. 
