DIPTEEA. 59 



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 Dichaeta ; that is, 

 those flies having two-fibred suckers. Among these are classed 

 the (Estri, the Conopes, and the flies properly so called. 



The genus (Estrus, the Gad, Bot-fly, or Breeze, comprises those 

 formidable insects which attack the horse, the sheep, and the ox.* 

 The labours of Heaumur, in his admirable Memoirs, and those of 

 M. Joly, Professor of Zoology to the Faculte 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- 



rig. 41. Horsefly, male ( (Estrus (yastrus) equi). Fig. 42. Horsefly, female ( (Estrus (gastrus) equi). 



fly ((Estrus equi), represented in Figs. 41, 42, which is 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 antennae 

 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. 



This species is found in France, in Italy, and also in the East, 

 especially in Persia, and rarely in this country. During the months 

 of July and August, the (Estrus frequents pastures, and de- 

 posits its eggs chiefly on the shoulders and knees of horses. In 

 order to do this, the female suspends herself in the air for some 

 seconds over the place she has chosen, falls upon it, and with* 

 her abdomen bent, sticks her eggs to the horse's hairs by means 



* Mr. Bates, in his interesting " Naturalist on the Amazons," mentions an (Estrus 

 as occurring in those regions, which deposits its eggs in the human flesh, the larva 

 causing a swelling which resembles a boil. Er>. 



