DIPTERA. 85 
tution delicate. They live principally in the thickest part of woods, 
on grasses, and aquatic plants. Fearing the lustre and warmth of 
the sun, they never draw the nectar from flowers. Their flight is 
feeble, and they never indulge in those joyous ethereal dances 
which we have mentioned when speaking of the preceding groups. 
Their life is generally melancholy, obscure, and hidden. Some of 
them seek decomposed animal and vegetable substances, others 
living vegetables. 
We shall only be able in this immense group of Muscide to 
mention a few types which are interesting from various reasons, 
such as the Helomyze, the Scatophage, the Ortalides, the Daci, 
and the Thyreophore. 
The Helomyze (Fig. 64) live in 
the woods. Their larvee are developed 
in the interior of fungi. Réaumur 
studied the larvee of the Truffle Helo- 
myza. The head of this fly is ferru- 
ginous, its thorax is of a brownish 
grey, its shoulders of a brownish yel- 
low, its wings brownish, the abdomen 
yellow and brown, and the feet red. 
The larve of these insects commit 
depredations for which gourmands 
will never forgive them, destroying, 
as they do, their truffles. When one 
presses between one’s fingers a 
truffle that is in a too advanced 
state, one feels certain soft parts 
which yield under pressure. On 
opening the truffle, the larvee of the 
insect of which we are speaking 
will be found inside. These larvae 
are white and very transparent. \ 
Their mouth is armed with two black Fig. 64.—A species of Helomyza. 
hooks, by means of which they dig 
into the truffle in the same way as other larve dig into meat. 
The excretions of these little parasites cause the truffle to become 
decomposed and rotten. In a few days the larve are full-grown. 


