70 THE INSECT WOELD. 



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, "is 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. 



Beaumur, 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 larvae. 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 larvae 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 calljils de la merge. 



