2 S 2 THE OPEN COUNTRY 



with many single-haired warts, while the white abdomen is marked with deep black 

 glistening spots. This pest, which is only too frequently to be met with in July and 

 August near flocks of sheep and goats, quietly sitting on stones or tree-trunks, lays 

 its eggs on the nostrils of those ruminants, whence the grubs pass upwards into the 

 brain, where they undergo their development. Yet another pest is the ox-warble 

 fly (Hypoderma bovis), which is principally black in colour with reddish yellow and 

 black hairs, except on the abdomen, where they are grey and yellow. The eggs are 

 deposited on cattle in whose skin the larvae produce abscesses of the size of a pigeon's 

 egg, where they remain for some nine months. According to one view, the larvae 

 so soon as hatched from the eggs laid in the hair of the infected beast, at once 

 proceed to bore their way through the skin of the back, and then eventually form 

 the warbles. On the other view, they are licked off from the hair by the tongue 

 of the animal, swallowed, and carried into the stomach and intestine, whence they 

 bore their way through the intervening tissues till they reach the muscular layer 

 beneath the skin of the back. The latest observations confirm the general correct- 

 ness of the second view. The eggs, instead of being hatched externally, are, 

 however, licked off from the hair by the infected cattle, and do not develop into 

 larvae till they have entered the first compartment of the stomach. Here they 

 may be found soon after the swarming period of the flies, but later on the greater 

 number of them migrate to the throat, where they wander for several months 

 (July to November, or even February) in the tissues underlying the mucous 

 membrane, which they have previously penetrated. Their next migration is more 

 extensive, and they gradually make their way from the submucous tissues of the 

 throat or entrance of the stomach right through the body till they reach the spinal 

 canal, this migration taking place, as a rule, between December and March. 



After a residence of three months in the spinal canal, the larva? again shift 

 their quarters — usually between January and June — this time reaching their final 

 station beneath the skin of the back, where they form the " warbles," subsequently 

 piercing the skin to fall to the ground and undergo the pupa stage, and ultimately 

 to develop into adult flies. A single female of this fly is capable of laying eggs 

 enough to infect an entire herd; and so much are these flies dreaded by cattle, 

 that even the imitation of their buzzing will cause a herd to stampede. The horse 

 bot-fly (Gastrophilus equi), which somewhat resembles a bee in general appearance, 

 is about half an inch in length, with a brown cross-band on its whitish wings, and 

 two spots of the same colour at their tips. The eggs are laid on the hair of the 

 horse's fore-legs, and being licked up from there, enter as larva? into the alimentary 

 canal, along which they slowly pass until they pass out with the droppings, when 

 they turn into pupa? underground. 



To the family of the typical flies belong the flesh-flies, whose larvas dwell in 

 decaying flesh. Among these may be mentioned the carcase - fly (Sarcophaga 

 mortuorwm), which develops from the ill-famed carcase-worm, and has a reddish 

 yellow head, a steel-blue abdomen, and yellow antennae. This noisome fly deposits 

 its eggs in bodies buried a short distance below ground, but is fortunately rare. 

 Better known is the grey flesh-fly (S. carnaria), which is common everywhere in 

 summer and autumn, and, in place of laying eggs, brings forth living maggots. 

 These grubs, which have sometimes been observed in abscesses of the human ear, 



