348 VETERINARY HYGIENE 



of the day, when the adult female flies are abroad for egg-laying 

 purposes, the sheep stand with their noses in the furrow and access 

 to their nostrils is denied the intruder, which is loth to enter a 

 virtual " pit " in the soil. 



In the case of very valuable sheep it is not uncommon to have 

 to trephine the nose or sinuses and remove maggots with forceps. 



SHEEP BLOW-FLIES. 



Sheep maggots are the larvae of the " green bottle fly," Lucilia 

 seriatica or L. casar, or less commonly of the " blue bottle," 

 Caliphora. The female lays as many as 500 eggs in clusters of 

 50 on the wool of the sheep; heavy, greasy wool and sheep with 

 soiled quarters being especially attractive to them. 



Sheep badly infested with keds, with shoulders and loins 

 denuded of wool by rubbing or biting, are frequently " struck " 

 on the bare parts. Lambs, sick sheep, and those lame, as from 

 foot-rot, are more often attacked than are healthy vigorous sheep. 

 The life-cycle is completed in about 28 days, the period from egg 

 deposition to fully grown maggots taking 14 days. A number 

 of generations is hatched during one season. Several species of 

 blow-flies attack domestic animals and man, laying their eggs about 

 the anus, &c. Wounds especially attract them, and horses with 

 greasy heels and cankered hoofs and those with the prepuce coated 

 with inspissated smegma are very liable to become infected with 

 species of blow-fly maggots. Sheep dogs with foul hindquarters 

 and hair matted with excreta are specially liable to be " struck." 



From May to August is the blow-fly season in this country, 

 July and August being about the worst months. The maggots 

 literally live upon their host, and sheep if much neglected eventually 

 die; such cases are, however, uncommon, but depreciation in value 

 owing to the set-back badly " struck " sheep suffer is certain. It 

 is generally considered that a " struck " sheep is a magnet to other 

 blow-flies. Immediately before a fall of rain on a sultry, vapid 

 day, or just prior to a summer thunderstorm, when the atmosphere 

 is very oppressive, the flies are particularly annoying, and sheep may 

 be seen huddled together with their heads down, and frequently 

 stamping, in an endeavour to protect themselves by congregation. 



PREVENTIVE MEASURES. Some means of shelter from the mid- 

 day sun should be provided, and even morning and evening feeding 

 may be necessary, the middle part of the day being spent in a park 

 or wood where abundant overhead foliage affords a cool shade. 

 Sheep folded in the middle of an open field for the whole of the 



