442 THE NATURAL HISTORY 



perish in this dangerous transit, but sometimes as 

 many as a hundred bots succeed in attaching them- 

 selves by means of their two anal hook-like processes 

 to the mucous membrane of the stomach, chiefly near 

 the pylorus. Here they remain till they are full 

 grown, and as they are supposed to feed on the 

 chyle, they are probably not productive of much 

 discomfort to the horse or any material derangement 

 of its health. When they are prepared to assume the 

 pupa state, they relax their hold, are carried through 

 the intestinal canal, and discharged with the faeces. 

 At this stage a few individuals once fell into our 

 possession, these were placed in a vessel having a 

 piece of net strained over the top, and a few inches 

 of loose mould at the bottom, they soon disappeared 

 in the mould to become pupae, and before the end of 

 the summer emerged in the perfect state. In this way 

 we first became acquainted with GasteropJtiliis Equi, a 

 hairy fly of a dingy yellowish colour with a black 

 patch on the thorax, transverse black bars on the 

 upper surface of the abdomen and symmetrically 

 clouded wings, and we have since then had many 

 opportunities of watching the insect hovering near the 

 horses in the Downpark meadows. Another species of 

 the genus, Gasterophilus kczmoroidalis, is also parasitic 

 on the horse, and the latter, though no Entomologist, 

 is quite capable of identifying his tormentor at a 

 glance. It is on his lips that this fly seeks to deposit 

 its eggs, and no sooner does it approach him for this 

 purpose, than he endeavours to drive it away by 

 violently tossing his head up and down, or gallops 

 about to avoid it. Needless to say, that in spite of 

 his resistance, the fly sooner or later accomplishes its 

 object, and the after history of the insect is similar to 

 that of the preceding species. 



The members of the last important division in this 

 order, as curious in their outward forms as in their 

 economy, differ from all the other Diptcra in their 



