INSECT ENEMIES OF LIVE STOCK 177 



without food, their mouths being, for the most part, very 

 rudimentary, and in some cases wanting. 



The adult horse hot fly, Gastrophilus equi, is about 

 three-quarters of an inch in length ; its transparent wings 

 are spotted, in such a way as to give them the appearance 

 of being crossed by an irregular, transverse band. The 

 hairy body is relieved from a uniform brown colour by 

 the whitish front to the head and three rows of blackish 

 spots on the abdomen, though the abdominal colouring is 

 subject to considerable variation. In the male, the abdomen 

 may be light brown, or even quite yellow, with very distinct 

 brown spots ; whilst, in the female, the brown segments 

 may have a marginal series of yellow spots. 



The female fly, when about to oviposit, hovers near a 

 horse in a nearly vertical position. Then, with a sudden 

 dart, it fixes almost instantaneously a single egg (fig. 48) 

 to a hair, in some place where it may easily be reached by 

 the horse's tongue, and then retreats a yard or two, where 

 it hovers till another egg can be laid. By the repetition of 

 this operation, at short intervals, a large number of eggs are 

 laid. At first they are almost white, but they soon change 

 to pale yellow, and are marked with a series of transverse, 

 raised ridges. Each egg is about 1'25 millimetres long, 

 obliquely truncate at the free end, and bluntly pointed at 

 the other ; it consists of two parts, the egg proper, and a 

 pair of lips or valves, which close round the hair and give 

 attachment. The presence of these eggs causes a consider- 

 able amount of irritation to the horse, which seeks relief 

 by licking the afflicted parts. The eggs themselves are 

 rarely removed, but the friction and moisture of the horse's 

 tongue, essentials to hatching, cause the lid or operculum, 

 covering the free end of each egg, to open, and the con- 

 tained larva is carried into the horse's mouth. These larvss 

 are slender and worm -like, and so transparent that their 

 internal organs may be plainly seen. Growth is rapid, and 

 probably takes place at the expense of the mucus, secreted by 



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