62 DR. LEGEAR'S STOCK BOOK. 



"The common gad-tly ((iastropilius equi) attacks the animal 

 while grazing late in the summer, its object being, not to derive 

 sustenance, but to deposit its eggs. This is accomplished hy 

 means of a glutinous excretion, causing the ova (egg) to ad- 

 here to the hairs. The parts selected are chiefly those of the 

 shoulder, base of the neck, and inner part of the forelegs, espe- 

 cially about the knees, for in these situations the horse will have 

 no difficulty in reaching the ova with its tongue. When the 

 animal licks those parts of the coat where the eggs have been 

 placed, the moisture of the tongue, aided by warmth, hatches the 

 ova, and in something less than three weeks from the deposition 

 of the eggs the larvae have made their escape. As maggots they 

 are transferred to the mouth, and ultimately to the stomach, with 

 food and drink. A great many larvae perish during this passive 

 mode of immigration, some being dropped from the mouth and 

 others being crushed in the fodder during mastication. It has 

 been calculated that out of the many hundreds of eggs deposited 

 on a single horse scarcely one out of fifty of the larvae arrive 

 within the stomach. Notwithstanding this waste the interior of 

 the stomach may become completely covered (cuticular portion) 

 with bots. Whether there be few or many they are anchored in 

 this situation chiefly by means of two large cephalic hooks. After 

 the bots have attained perfect growth they voluntarily loosen 

 their hold and allow themselves to be carried along the aliment- 

 ary eanal until they escape with the feces. In all cases they 

 sooner or later fall to the ground, and when transferred to the 

 soil they bury themselves beneath the surface in order to undergo 

 transformation into the pupa condition. Having remained in 

 the earth for a period of six or seven weeks they finally emerge 

 from their pupal-cocoons as perfect dipterous (winged) insects 

 the gad-fly. It thus appears that bots ordinarily pass about eight 

 months of their lifetime in the digestive organs of the horse." 



It is very common to hear bystanders declare, when a horse is 

 suffering from what is commonly called colic, "that the horse 



