Fig. 63.—Anthomyia pluvialis.
In this group of Diptera we will first say a few words about the Anthomiæ. These flies are to be found in most gardens, and on all flowers, particularly on the heads of Compositæ and Umbelliferæ. They often unite in numerous bands in the air, and indulge in the joyous dances to which love invites them. The females deposit their eggs in the ground, and their larvæ are there quickly developed. The latter suspend themselves to certain bodies, the same as some lepidopterous chrysalides, in order to transform themselves into pupæ.
The Anthomyia pluvialis ([Fig. 63]) is from two to four lines in length, and of a whitish ash-colour. Its wings are hyaline, the thorax has five black spots, and the abdomen three rows of similar spots.
We will stop a moment with the Pegomyiæ, which are very interesting in the larva state, and which excited the interest and sagacity of Réaumur.
The cradle of these Diptera is the interior of leaves. They work as the miners of the vegetable world, in the parenchyma or cellular tissue of the leaf, between the two epidermal membranes. The henbane, the sorrel, and the thistle, especially nourish them. If one holds a leaf in which one of these miners has established itself against the light, one sees the workman boring the vegetable membrane. Its head is armed with a hook, formed of two horny pieces, and with this hook it digs into the parenchyma of the leaf. The effect of this digging is visible, as those places become by degrees transparent. Each blow detaches a small portion of the substance of the leaf. It is thus that these miners hollow out galleries for themselves, in which they find shelter, food, and security. Some are changed into pupæ in the gallery which they have hollowed out, others go out of the leaves when they are near their final transformation.
Fig. 64.—A species of Helomyza.
Section of Acalyptera.—The Acalyptera, which are the last of the great tribe of Muscidæ, comprehend the greater number of these insects. Their constitution appears to be peculiar and slow. 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 Muscidæ to mention a few types which are interesting from various reasons, such as the Helomyzæ, the Scatophagæ, the Ortalides, the Daci, and the Thyreophoræ.