792 PAEASITIC DISEASES. 



That bots are capable of giving rise to severe disease in the 

 horse there cannot be any reasonable doubt, but it is not often 

 that the disorder is correctly diagnosed, since it is only by the 

 passage of the larvae, or by their adherence to the verge of the 

 anus, that the practitioner can be made aware of their presence. 

 We are not called upon to dwell on this fact of the subject in 

 the present chapter, but may remark in passing that Mr. J. S. 

 Woods, V.S., has published in the Veterinarian a case of tetanus 

 in a mare associated with the larvae of (Estrus equi, and Mr. J. T. 

 Brewer, V.S., has also given a case in the same journal, where 

 the duodenunx of a horse was perforated by bots. 



Several other species of (Estrus victimise the horse ; one of the 

 most formidable of these being the CE. hmmorrhoidalis. This 

 fly is especially annoying in the initiatory stages of the attack, 

 because, unlike the common species, it selects the lips and 

 nostrils as the principal locality for the lodgment of the ova. 

 According to Bracey Clark the mere sight of the insect produces 

 extreme agitation, the horses wildly galloping to and fro in their 

 usually vain endeavours to evade these winged tormentors. 



The common bot-fly of the ox {Oestrus hovis) passes through 

 transformations similar to those undergone by the gadflies of 

 the horse. It differs, however, in one important particular ; for, 

 in place of acquiring its larval condition as a bot within the 

 stomach, it takes up its residence for that purpose beneath the 

 animal's hide. In this situation its presence gives rise to the 

 formation of small tumours, termed warhles. The facts, in short, 

 are as follows : — Selecting, as before remarked, young beasts in 

 good condition, the fly lights on the back on either side of the 

 spine. The animal darts away in alarm, often bellowing furi- 

 ously and frightening its companions. The whole herd forth- 

 with rush about in a frantic manner; and it is said that the 

 mere buzzing of the insects is sufficient to render yoked animals 

 quite unmanageable. In a short time the insect succeeds in 

 perforating the skin by means of an ovipositor, one egg being 

 deposited in each opening. After a time the egg is hatched, ana 

 the young during growth produces sufficient inflammation to 

 lead to the formation of the well-known warhles. Within the 

 tumour the bot is placed with its head downwards, its tail being 

 applied to a small external opening in the warble, in order that 

 it may receive sufficient air for the purposes of respiration. 



