Fig. 40.—Larvæ of a Helophilus.
What an eventful life! what a life full of changes and turns of fortune is that of these insects, which pass the first and longest period of their existence under water, another part of their life under the ground, and, finally, after having existed in these two elements, enjoy, high in the air, the pleasures of flight!
The third group of Brachycera is that of the Dichæta; that is, those flies having two-fibred suckers. Among these are classed the Œstri, the Conopes, and the flies properly so called.
The genus Œstrus, the Gad, Bot-fly, or Breeze, comprises those formidable insects which attack the horse, the sheep, and the ox. [15] The labours of Réaumur, in his admirable Memoirs, and those of M. Joly, Professor of Zoology to the Faculté des Sciences de Toulouse, who published some most valuable researches on this subject, in 1846, will guide us in the following brief explanation.
The following is the description given by M. Joly of the Gad-fly (Œstrus equi) represented in Figs. [41], [42], which are taken from a drawing which accompanies that naturalist's Memoirs.
The head of this insect is large and obtuse; the face light yellow, with whitish silky fur; the eyes blackish; the antennæ ferruginous; the thorax grey; and the abdomen of a reddish yellow, with black spots. The wings are whitish, not diaphanous, with a golden tint, and divided by a winding band of blackish colour. The feet are palish yellow.