82 MANUAL OF MODERN FARRIERY 



its healthy condition no artificial aid is necessary to 

 enable it to perform its office. If the opinion of Mr 

 Clark were correct, what would supply the place of 

 those parasites during that portion of the year when 

 the grub assumed its perfect condition ? 



Post-mortem dissection has proved that bots are 

 not so inoffensive as Mr Clark supposed ; as it has 

 been found that horses which have been infested with 

 these grubs had ulcers of considerable extent in the 

 muscular coat of the stomach. 



SYMPTOMS AND HABITS. The progress of the dis- 

 ease generally manifests itself gradually ; the horse 

 becomes hide-bound, his coat becomes rough and un- 

 healthy, he loses flesh and strength, although he feeds 

 with his usual appetite, and has frequently a tickling 

 cough. 



CAUSE. The bots are a species of gad-fly called 

 cestrus equi by naturalists, which may be observed in 

 the month of July flying actively about the legs of 

 horses in the fields. These flies are represented (Plate 

 x, fig. i), which is the common gad-fly. They may 

 be seen flying rapidly towards the sides and knees of 

 horses. These are the females depositing their eggs 

 in the hair, to which they adhere by a glutinous fluid 

 by which they are surrounded (figs. 2, 3). In a few 

 days the eggs are hatched, and the minute grubs or 

 caterpillars which they contain are set at liberty. 

 This operation is performed by the horse, which, in 

 licking himself, bursts the eggs, and the caterpillar 

 adheres to his tongue, and in the operation of eating, 

 the little animal is carried into the stomach along with 

 the food. These caterpillars are provided with a small 

 hook on each side of their mouths, and by means of 

 which they cling pertinaceously to the cuticular portion 

 of the lining of the stomach (see fig. 4) ; and so tena- 



