1900] sheep's nostril fly. 91 



special season for the maggots to leave the nostrils ; but they may be 

 found at other times, and maggots of all ages, it is stated, may be 

 found in the winter time. Amongst inquiries sent me about this 

 attack forwarded on May 12th, one, in 1889, was accompanied by six 

 maggots of different sizes up to five-eighths of an inch long, taken from 

 one sheep. 



They are stated by various writers to remain for about ten months 

 in the nose cavities, but this is not absolutely proved. 



After the maggot has escaped from the nostrils and fallen to the 

 ground, it bores into it for an inch or two, and there contracts and 

 changes to a imparium, or chrysaUs-case, smooth and hard, and of a 

 dark colour, within which the fly develops, and from which it emerges, 

 according to various observers, at very different lengths of time— some 

 giving three or four weeks, some more than twice that time, as the period 

 of development, according to state of weather. 



The Sheep's Nostril Fly {(Estnis oris) is from about two-fifths to 

 half an inch in length, and slightly hairy. The upper part of the head 

 and body between the wings of some shade of grey or dull yellow, 

 spotted or mottled with dark markings. The abdomen yellowish, or 

 white, mottled with dark brown or black ; the under side similarly 

 coloured, but " with a dark spot in the middle of each ring." Legs 

 brown or yellowish brown ; wings transparent, and when at rest 

 extend beyond the body. Mouth wanting. There is a good deal of 

 difference in the exact shades of colour described by various writers ; 

 from such as I have myself examined I should say that the fly might 

 be described as spotted, or mottled, with ash-grey, and black between 

 the wings, and the abdomen also spotted with black and yellowish 

 white, with a silvery lustre when alive. 



This attack is considered not to be serious, excepting in occasional 

 instances, as where there may be an unusual number of maggots, yet 

 the symptoms recorded as accompanying even a common amount of 

 maggot presence show a degree of annoyance to the sheep that is much 

 better avoided. The discharge from the nose, the throwing the head 

 upwards and shaking it, and the sneezing and snorting, all show great 

 uneasiness. Sometimes there is a good deal of trouble, amounting in 

 severe cases to difficulty of breathing from stoppages occasioned by 

 presence of the maggots, or inflammation of the mucous membrane ; 

 but, excepting (as above mentioned) where there are many maggots, 

 the attack does not appear to be often fatal, and when the cause of the 

 trouble has been got rid of in natural course the sheep recovers. 



I do not remember having had information sent me of more than 

 six larvae being present together in any case of nostril infestation 

 reported ; and in Dr. Cooper Curtice's paper, previously quoted,'^ he 

 * For reference to title, see ante, footnote, p. 90. 



