8o 



notwithstanding the waste, the interior of the horse's stomach may become 

 completely covered with the larvae commonly termed " bots." 



When the bots, which hold on to the lining of the stomach by means of 

 two large hooks, are perfectly grown, they release themselves, and are carried 

 through the intestines along with the excreta, and thus they finally fall to the 

 ground. They then bury themselves below the surface, in order to undergo 

 a transformation from the condition of the bot, to that of the pupa or 

 chr>^salis. When they ha^•e remained thus buried for six weeks, they make 

 their way out of their enclosing cocoons, and emerge as perfect gad-flies. 

 The male insects die, but the females live long enough to deposit their eggs, 

 which are generally about forty in number. The bot passes about eight 

 months of its existence in the stomach, where it is present in the winter 

 months. It leaves in spring or early summer. The fly is developed from 

 June to September, and after the latest females have appeared, all perish in 

 October. Not uncommonly, the presence of bots in the stomach of the 

 horse gives rise to considerable mischief. When very numerous, they may 

 set up serious disease, sometimes even perforating the walls of the intestines. 

 It is not always possible to diagnose the presence of bots in the stomach, 

 but not unfrequently they may be seen in the excrement, or adhering 

 around the anus. When there is reason to suspect their presence in very 

 large numbers, it is well to place a piece of rock salt in the horse's manger, 

 and to administer a drench, consisting of spirit of ether two ounces, of 

 glycerine of carbolic acid three drachms, and of linseed oil a pint. This- 

 may be repeated once every day for four days. 



The accompanying pictures show the various forms assumed by the 

 oestrus equi. A is the larva or bot, B is the pupa case, C is the male fly, and 

 1) is the female fly. There is another species of gad-fly called the oestrus 

 ha:morrhoidalis, which deposits its eggs on the lips and nostrils of the horse. 

 We need not speak at length here of the bot-fly of the ox, but may mention 

 that, unlike the bot-fly of the horse, it passes its larval stage as a bot beneath 

 the skin of its host, and it is this larva whose growth causes the appearance of 



