1919.] 229 



OBSERVATIONS ON THE HORSE BOT-FLY, GASTTiOPHILUS EQVI F. 

 BV A. II. HAMM, i'.E.S. 



The phoiioinenally fine and hot weather (lurint>- the first half of 

 August last was evidently highly favourable to that well-known ])est, 

 the Bot-fly (GasfropJiih(s equi F.). My holiday falling within the 

 same period enabled me to give some attention to and make a few 

 observations on this species. 



On. August 7th, in Hogley Bog, near Oxford, 1 netted one male and 

 two females from round the legs of a mare turned out to grass. The 

 flies are very easy to catch if only the horses will stand still for a 

 moment and allow one to approach ; but this was by no means easy, for 

 at the least movement of the net the horse invariably galloped away, so 

 that the stalking had to be begun over again. However, with persistence 

 antl patience the three specimens were at length secured. The number 

 of eggs laid on this ixirticular horse was truh"- astonishing. From below 

 the knee to just above the hoof they were so close together that they 

 entirely covered the hair on the anterior surface of the fore legs. Many 

 were also laid on the hind legs, shoulders, hind-quarters, and a few even 

 on the mane. I di"ew the owner's attention to hei- condition and he 

 promised to do what he could to remove them. I had another look at 

 her on the lOth when she was fairly free from eggs, and no bot-flies 

 were in attendance. I did not see her again until the 23rd, which was a 

 very dull and not over warm day, l)ut the eggs that had again been 

 deposited were eijualh' or even more numerous than those observed 

 on the 7th. 



On August 10th on Lye Hill, adjoining Hogley Bog, a number of 

 farm horses, turned out to grass, were all huddled together under the 

 shade of some large elm trees, and owing to the 2:)resence of Haematopota 

 and various other flies they were extremel}' restive. They allowed me, 

 however, to approach near enough to see that several female bot-flies 

 were busy ovipositing. Every horse had a large number of eggs attached 

 to various parts, mostly the fore legs below the knees. 



On August nth I went to Newdniry for a few days. Crossing 

 Victoria Park, close to the to\\n, on the lUth, I saw a group of four 

 or five horses close together in the shade of an avenue of lime trees. 

 The shrill bee-like hum of the bot-flies in attendance about the horses' 

 legs Avas perfectl}' audible at several yards distance. By dint of patience 

 and caution 1 secured five specimens, all females. All the horses were 

 much infested with their eggs, as before mainly on the fore legs, below 

 the knees. At various places in the neighbourhood I examined many 



