THE WARBLE-FLY 149 



The following remedies will considerably diminish the access 

 of bots : — During autumn (July to October) and especially in 

 bright weather, the horse's coat should be searched at least 

 twice a week, and the shoulders and knees washed with warm 

 water, to hatch out any ripe eggs. Checks have been proposed 

 to hinder the horse from reaching those parts of his body 

 which are the favourite egg-laying places of the bot-fly. There 

 is no method known of destroying bots in the stomach, as they 

 resist all drugs which it is safe to employ. Any bots that 

 appear beneath the tail should be removed at once. 



The warble-fly and the bot-fly belong to the same family 

 (CEstridae or breeze-flies). QEstridas are closely related to the 

 Muscidas, of which the blow -fly is a familiar example, but 

 differ in the following points : — CEstrid flies are nearly always 

 hairy, and more or less resemble bees ; the mouth-parts are 

 reduced to vestiges, three simple eyes are conspicuous on the 

 forehead, and the antennae are sunk in deep grooves. The 

 larvae are parasitic upon quadrupeds (ox, horse, sheep, deer), 

 and generally inhabit some part of the alimentary canal of 

 their host. Nearly twenty European species are known. 



30. THE WARBLE-FLY (Hypoderma bovis) 



This insect belongs to the same family (CEstridae) as the 

 bot-fly of the horse, and in every stage of growth it shows a 

 similar organisation, though with differences which adapt it to 

 its special needs. It is commonly seen only during the larval 

 or maggot stage, when it lies within the skin of the ox, mostly 

 along the back. The inflammation set up by the presence and 

 movements of the parasite occasions a formation of pus, and 

 upon this the maggot subsists. The cavity in which it lies 

 communicates with the outer air; at first the tube of com- 

 munication is narrow, but it becomes much wider as the 

 maggot increases in size. It is by this passage that the maggot 

 escapes, when its transformation is at hand. 



The eggs of the warble-fly are laid in summer or autumn. 

 Many may be hatched upon one beast, and it is remarked that 

 young and vigorous cattle are more often infested than others. 

 The attack of the female fly has been generally believed to 

 cause whole herds of cattle to rush about in the greatest alarm, 



