

70 THE INSECT WORLD. 
deposit their eggs on the very food which was intended for others. 
Their larvae, which are soon hatched, make great havoc among 
the provisions gathered together in the cave, and cause the legiti- 
mate proprietors to die of starvation. 
“This instinct,” says M. Macquart, “1s accompanied by the 
greatest agility, obstinacy, and audacity, which are necessary to 
carry on this brigandage ; and on the other hand, the Hymentop- 
tera, seized with fear, or stupefied, offer no resistance to their 
enemies, and although they carry on a continual war against dif- 
ferent insects, and particularly against different Muscides, they 
never seize those of whom they have so much to complain, and 
which, nevertheless, have no arms to oppose them with.” 
The Sarcophaga are a very common family of Diptera, and are 
chiefly to be found on flowers, from which they steal the juice. 
The females do not lay eggs, but are viviparous. 
Réaumur, with his usual care, observed this remarkable instance 
of viviparism proved in a fly, which seeks those parts of our houses 
where meat is kept to deposit its larve. This fly is grey, its 
legs are black, and its eyes red. 
When one of them is taken and held between the fingers, there 
may often be seen a small, oblong, whitish, cylindrical worm 
come out of the posterior part of the body, and shake itself in order 
to disengage itself thoroughly. It has no sooner freed itself than 
the head of another begins to show. Thirty or forty sometimes 
come out in this manner, and, on pressing the abdomen of the fly 
slightly, more than eighty of these larvee may sometimes be made to 
come out in a short space of time. If a piece of meat be put near 
these worms, they quickly get into it, and eat greedily. They 
grow rapidly, attaining their full size in a few days, and make a 
cocoon of their skin, from which in a certain time the imago 
issues. If the body of one of these ovoviviparous flies (for the 
eggs hatch within the parent) be opened, a sort of thick ribbon of 
spiral form is soon seen. This ribbon appears at first sight to be 
nothing but an assemblage of worms, placed alongside of and 
parallel to one another. 
Each worm has a thin white membraneous envelope, similar to 
those light spiders’ webs which flutter about in autumn, and 
which the French call fils de la vierge. 
