430 YETEEINAEY HYGIENE 



the stomach, for choice to the cuticular coat, though 

 sometimes they are found on the villous area. Here 

 they remain 9 or 10 months, then let go their hold, and 

 reach the ground with the faeces ; the pupal stage is passed 

 in the ground, and the fly emerges in 5 or 6 weeks. 



It is difficult to fix the amount of harm done by horse 

 bots ; the stomach is frequently found to contain a con- 

 siderable number of the larvEe without apparently causing 

 inconvenience, but there is abundant evidence that they 

 can produce harm, and every attempt should be made by 

 destroying the eggs on the skin at frequent intervals to 

 prevent the hatching out process. For this purpose horses 

 at grass might be dealt with once a week, by being caught 

 up and a singeing lamp passed over the egg area. The dress- 

 ing used for oxen may also be employed to repel the fly. 



Gastrojihilus hcemorrhoidalis is a second species of bot-fly 

 which attacks the horse. The female lays her eggs about 

 the lips, and the larvse are easily conveyed into the mouth, 

 where they may fix themselves in the pharynx, or preferably 

 the rectum. Their removal from either of these places is 

 not difficult if their presence is suspected. 



CEstrus ovis, the Sheej) Nostril Fly, deposits eggs ready to 

 hatch, or larvae, on the nostrils of sheep ; the larvae crawl up 

 the nasal chambers and accommodate themselves in the 

 frontal sinuses and horn cores. This occurs about July, and 

 the maggots remain in the sinuses until the spring, when 

 they migrate into the nasal chamber and are sneezed out ; 

 in six or eight weeks after pupation they develop into a fly. 



This fly greatly alarms sheep which fight against it, 

 carry their noses low, and take refuge wherever they can 

 crowd together with their heads near the ground. The fly 

 attacks with great rapidity, circling around the sheep, and 

 watching for the needful opportunity for depositing the 

 maggot. 



Sneezing, discharge from the nose, and staggering gait 

 are very suggestive symptoms of the presence of the larvae 

 of this fly. Eemedial treatment is difficult. For pre- 

 vention the smearing of the nose with tar is effectual, but 

 obviously difficult of application with large flocks. 

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