


DIPTERA. 85 
tion 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 search for decomposed animal and vegetable substances, 
others living on vegetable matter. 
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 Scatophagi, ‘He: Ortalide, the Dact, and 
the Thyreophore. 
The Helomyzas (Fig. 64) live in a 
the woods. Theirlarvz aredeveloped \ 
in the interior of fungi. Réaumur b 
studied the larva 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 larvee 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 larve of the 
insect of which we are speaking 
will be found inside. These larvee 
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. 


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