60 THE INSECT WORLD. 



of a glutinous liquid with which they are provided, and which 

 soon dries. This is repeated at very short intervals. It often 

 happens that from four to five hundred eggs are thus deposited 

 upon the same horse. Guided by a marvellous instinct, the 

 female (Estrus generally places her eggs on those parts of the 

 horse's body which can be most easily touched with the tongue, 

 that is, at the inner part of the knees, on the shoulders, and rarely, 

 on the outer part of the mane. 



Horses are much afraid of the attacks of these insects. Their 

 skin contracts where the (Estrus deposits its eggs, and the effects 

 of the bite soon become serious. 



The eggs of the (Estrus, which are white and of conical form, 

 adhere to the horse's hair as shown in Fig. 43. They are 

 furnished with a lid, which at the time of hatching opens, to 

 allow the exit of the young larva, which takes place, according 



Fig. 43. Eggs of the Gad-fly ((Estrus (gastrus) equi] deposited ou tlie liairs of a, horse. 



to M. Joly, about twenty days after they are deposited. In fact 

 it is not in the egg state, but really in that of the larva, that 

 the horse, as we shall explain, takes into his stomach these 

 parasitical guests to which nature has allotted so singular an abode. 

 When licking itself, the horse carries them into its mouth, and 

 afterwards swallows them with its food, by which means they 

 enter the stomach. It is a remarkable fact that it is sometimes other 

 insects, as the Tabani for instance, that by their repeated stinging 

 cause the horse to lick himself, and to thus receive his most cruel 

 enemy. In the perilous journey they have to perform from the 

 skin of the horse to his stomach, many of the larvae of the (Estrus, 

 as may be supposed, are destroyed, ground by the teeth of the 

 animal or crushed by the alimentary substances. There is hardly 

 one (Estrus in fifty that arrives safely in the stomach of the horse, 

 and yet if one were to open a horse attacked by (Estri, the stomach 

 would be nearly always found to be literally full of these larvse. 



