58 THE INSECT WORLD. 



the young larva, which takes place, according 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 

 his food, by which means they enter the stomach. It is a remarkable 

 fact that it is sometimes other insects, as the Tabania for instance, that 

 by their repeated stinging cause the horse to lick himself, and thus to 

 receive his most cruel enemy. In the perilous journey they have to 



Fig. 44. Portion of the stomach of the horse, and larvae of CEstrus (gasterophilus) equi. 



perform from the skin of the horse to his stomach, many of the 

 larvae of the CEstrus, as may be supposed, are destroyed, ground by 

 the teeth of the animal, or crushed by the alimentary substances. 

 There is hardly one CEstrus in fifty that arrives safely in the stomach 

 of the horse ; and yet if one were to open a horse which had been 

 attacked by the CEstri, the stomach would be nearly always found to 

 have many of the larvse sticking to its inside. Fig. 44, taken from a 

 drawing which accompanies M. Joly's Memoirs, represents the state 

 of a horse's stomach attacked by the Gad-fly larvse. 



The larvse are of a reddish yellow, and each of their segments is 

 armed at the posterior edge with a double row of triangular spines, 



