STOMACH BOTS. 201 



hour in the morning, varying with the time the sun rises, 

 from three to five A.M. My plan for observing these points 

 was to enclose the larvse, as I removed them from the 

 anus, into thin glass jars covered with gauze. Bracy Clark 

 said that ' after remaining torpid in the state of chrysalis, a 

 few weeks, the superfluous moisture being removed, and the 

 parts of the future insect being hardened by 'drying, it bursts 

 from its imprisonment, and the fly appears/ &c. I have 

 always seen the fly born on the eighteenth or nineteenth day. 



" The activity of the bots in my spontaneous vivaria was 

 very great, and with a buzzing noise they moved about and 

 then rested, and were especially vigorous and loud in their 

 buzz as the day advanced. In a state of nature this is a 

 provision to ensure the approximation of the sexes and fecun- 

 dation of ova," 



Clark declared that the bots were rather salutary than pre- 

 judicial in their effects on horses; but the view is untenable: 

 and my father has afforded evidence, that in warm countries, 

 and when horses are kept during the summer months at 

 grass, so as to receive a large supply of the bots' eggs in the 

 stomach, the parasites are prejudicial, and prevent the horses 

 being got into full condition for active work. My father's 

 experience is of such value to the practical man, that I hesitate 

 not to quote his remarks at some length. He says : " It 

 would be important to establish in what localities or countries 

 bots do, or do not, exist. Horses exposed on pasture in the 

 summer months will most probably be attacked by the fly. 

 This is certain in some countries where I have bought many 

 horses, viz., in Italy, also in the south of England; but it is 

 by no means so certain, I think, in other parts. I have pur- 

 chased many English horses, chiefly from Yorkshire or further 

 north, from breeders and farmers, &c., without discovering 

 the bots, though I carefully sought for them, and I am led to 



