This group includes a number of genera, but the following only possess sufficient interest to claim our attention. From the Tanystomæ we select the families of the Asilidæ, Empidæ, and Bombylidæ. As types of the Brachystomæ we select the Leptidæ and Syrphidæ.
| Fig. 33.—Tabanus autumnalis. | Fig. 34.—Chrysops cæcutiens. |
The chief characteristic of the Asilidæ is strength. All their organs combine to produce this quality, which they display only too much, being as formidable to cattle as the Tabani, but even surpassing those insects in natural cruelty.
The Asilidæ unceasingly attack other insects, and even those of their own kind. Their trunk is strong; one of the fibres of the sucker is furnished with small points, turned back, which are intended to hold firmly to the body into which it has entered. They carry on their devastations in the glades of woods and on sunny roads.
We will mention in this group Asilus crabroniformis ([Fig. 35]), an insect ten to twelve lines long, having a yellow head, black antennæ, and thorax of a brownish yellow. The three first segments of the abdomen are black, the second and third having a white spot on each side, the remaining segments are yellow. The wings are yellowish, spotted with black on the inner and hind margin. This species is common over the whole of Europe, and lives at the expense of caterpillars and other insects, of which it sucks the blood with the greatest voracity.
| Fig. 35.—Asilus crabroniformis. | Fig. 36.—Bombylius major. |
The Empidæ live in the same way as the Asilidæ, but the males are chiefly nourished by the juices of flowers.
"They wage war on other insects," says M. Macquart, in his "Histoire Naturelle des Diptères," "either when flying or running, and they seize their victims with their feet, which are formed in various ways, and well adapted for their purpose, but it is in the air that their hunting, as well as their amours, chiefly take place. They unite together in numerous companies, which during fine summer evenings whirl like gnats about the water's edge. A singular observation, however, that I have made on the Empis, is, that among the thousands of pairs that I have seen resting on hedges and bushes, nearly all the females were occupied in sucking an insect; some had hold of small Phryganeæ,[13] others of Ephemeræ, [14] and the greater part of Tipulæ."