The Insect World. Figuier Louis
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moisture. However it may be explained, the migration of these troops of insects are among the most astonishing phenomena of Nature.
Brachycera.
The Brachycera, from βραχυς, "short;" and κερας, "a horn" —these Diptera having short antennæ—are divided into four groups. In this subdivision the sucker is composed of six bristles. Amongst other families it includes that of the Tabanidæ; the insects belonging to which family are of remarkable strength, and possessed of daring and courage in the highest degree. Their wings are provided with powerful muscles, their feet are very strong, and their trunk is provided with six flat, sharp lancets. Distributed over the entire world, their instinct is everywhere the same, it is the desire for blood, at least in the females; for the males are not so warlike, they do no harm, but live on the juices of flowers. They are chiefly found in woods and pastures, and during the hottest part of the day in summer may be seen flying about seeking for their prey.
M. de Saint-Fargeau has described the manner in which the males fly. They may be seen flying hither and thither in the glades of woods, remaining for some time suspended in the air, then darting quickly and suddenly away a yard or two, again taking up the same immovable position, and in each of these movements turning the head to the opposite way from that in which they are going. This naturalist is certain that on these occasions they are watching for the females, which they dart upon. When they have succeeded in doing so, they rise so high as to be out of sight.
To this group belongs the genus Tabanus.
The first species we shall mention, Tabanus autumnalis (Fig. 33), a common species, is eight or nine lines in length, and of blackish colour. The palpi, the face, and the forehead are grey; the antennæ black; the thorax grey, striped with brown; the abdomen spotted with yellow; the legs of a yellowish white; and the outer edge of the wings brown.
Another species (Tabanus bovinus) is twelve lines in length, and of a blackish brown. The palpi, the face, and the forehead are yellow; the antennæ black, with a whitish base; the thorax, covered with yellow hair, is striped with black; the posterior edge of the segments of the abdomen pale yellow; the legs yellowish, with the extremities black, and the exterior edge of the wings yellow. This species is frequently met with in woods.
A third species, Chrysops cæcutiens (Fig. 34), which belongs to the same family, and of which the generic name Chrysops signifies golden-eyed, torments horses and cattle very much by biting them round the eyes. Its thorax is of a yellowish colour, striped or spotted with black; the abdomen yellow, and the eyes golden.
In the next group of the Brachycera the sucker is composed of four bristles, and the antennæ generally terminate in a point which appears to be rather a development than an appendage.
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.
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| 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.
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| 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."
The Empidæ have the trunk bent down, and resembling the beak of a bird; but the Bombylidæ, on the contrary, have the trunk extended straight in front.
The typical genus which has given its name to this latter group is easily to be recognised by the elegance of the fur which covers its body, the slenderness of its feet, and the length of its wings, which extend horizontally on each side of the body.
Much more common in hot climates than in the North, these insects, the larvæ of which are not yet known, take flight in the middle of the day, when the sun's rays are hottest. They fly very fast, making a dull buzzing sound, and hover over flowers, from which they draw the juices without settling.
Fig. 36 represents the Bombylius major, which is common enough throughout the whole of Europe. This insect is from four to six lines long, black, with yellow fur; the feet light yellow; and the wings have the edges bordered with a sinuous brown band.
The genus Anthrax, belonging to this family, has a different form to Bombylius. The body is much less hairy; the trunk is short and concealed in the mouth; the wings, which are very large, are clothed, at least in the principal genus, in a garb of mourning, sufficiently remarkable, in which the combinations of black and white are admirably diversified.
"Here," says M. Macquart, "the line which separates the two colours is straight; there it represents gradations, in other cases it is deeply sinuous. Sometimes the dark part shows transparent points, or the glassy part dark spots. This sombre garb, added to the velvet black of the body, gives the Anthrax a most elegant appearance; and while resting on the corolla