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set in. The eggs are deposited on all parts of the body, but preferably 

 on the fore-legs. They hatch upon the application of moisture and 

 friction supplied by the rubbing and licking of the horse, which also 

 results in the ingestion of the larvae, this taking place usually 9 to 11 

 days after oviposition, though it may be as early as 7 days or as late 

 as 96. They attach themselves to any part of the stomach, but the 

 last-stage bots are found mostly in the left sac. They continue to 

 drop from the host for a long period of time, and pupate in 

 protected places on the surface of the soil during a period of 

 40-60 days. 



The larvae of these three species are surprisingly resistant to 

 chemicals, the usual remedies for intestinal parasites giving negative 

 results, though soap solutions and nicotine sulphate are more effective. 

 Since contact substances capable of kiUing the larva would seriously 

 injure the stomach membranes of the horse, treatment for internal 

 use nuist necessarily be in the form of a fumigant. The use of carbon 

 bisulphide internally has been tried and approved by many veterin- 

 arians, being originally administered in 12-gram capsules surrounded 

 by aloes, the whole contained in 48-gram gelatine capsules. 



The Bureau of Animal Industry recommends the following proce- 

 dure : — A small amount of hay and a moderate amount of oats should 

 be given in the morning of the day preceding the treatment ; in the 

 evening food is withheld and a purgative given consisting of Barbados 

 aloes 1 oz., or raw linseed oil 1 pint. Next day at 6 a.m., 3 drams 

 of carbon bisulphide in a gelatine capsule is given, the dose being 

 repeated at 7 a.m. and at 8 a.m. This is especially satisfactory if 

 administered in the autumn, spring treatment being less effective, as 

 the full-grown larvae are more resistant and many of the nose-fly 

 bots have left the stomach and passed back to the rectum by that 

 time. 



Larvae of G. haemorrhoidalis may be removed from the anus 

 mechanically, but this is laborious and causes discomfort and soreness. 

 The use of enemas is ineffective. 



As a repellent, pine tar mixed with other material gave good results 

 against G. intestinalis and G. nasalis, and such mixtures may be used 

 to induce the flies to oviposit on parts of the body less accessible to 

 the horse's mouth. 



Various nose protectors are in use against G. haemorrhoidalis, but 

 there are objections to many of them. The simplest and best is a 

 piece of leather 4 to 6 inches wide suspended below the lips from the 

 bit rings. For animals in pastures a halter with a box-like arrange- 

 ment and throat cover has been devised to protect horses against 

 infestation by all three species. 



Kerosene oil, used as a wash, is ineffective in destroying the eggs, 

 but carbolic acid containing 2 per cent, phenol gave good results in 

 destroying eggs when applied to the infested parts of the host. 



Some investigators believe that the larvae of Gastrophilus are 

 able to cause swamp fever, by the excretion of a specific toxin, 

 since symptoms of typical swamp fever have been observed after the 

 administration of extracts of these larvae. This hypothesis is 

 strengthened by the fact that the distribution of the genus coincides 

 with that of the disease. Experimentally the most virulent reactions 

 have been obtained with the larvae of G. haemorrhoidalis. 



