26 INSECT PESTS 



the increase of Warble Flies is at the time when the 

 skin is perforated and the maggot is about to drop to 

 the ground. This may usually be done from February 

 to April. The maggot can be squeezed out with the thumbs 

 and crushed under foot, the wounds being dressed after- 

 wards v/ith mercurial ointment. This will have a distinctly 

 deterrent effect on these flies. Should there be a plague 

 of them, the beasts should be dressed all over with a 

 mixture of cart-grease and paraffin. The Warble Fly 

 itself is black in colour, with whitish hairs, very irritating 

 when coming against the skin. It has a blunt head and 

 strong, thick legs, the size across the outspread wings 

 being nearly an inch. (See Plate 4.) 



Sheep are subject to manj' insect parasites, our first 

 case being the Sheep's Nostril Fly {Oestrus ovis) which 

 is of the same family as the Bot Fhes just mentioned. 

 It is hairy in appearance and lightish brown in colour, 

 the wings measuring about an inch across when spread 

 out. The insect has the same blunt-looking head as the 

 Warble Fly, which arises in both cases from the fact that 

 these parasites in their mature state have no mouths, and 

 so do not feed as flies, all their mischief being wrought as 

 larvae. This however is more than enough. The poor 

 sheep have the same kind of uncanny presentiment about 

 the visits of the nostril fly, and as in the last case, exhibit 

 distress, rubbing their noses on the ground or seeking 

 dusty places in a desire to avoid attack. The nostril flies 

 pair in the early summer, and the egg, which is curved 

 or kidney-shaped, is laid around the sheep's nostrils. The 

 maggot at first is white and slender, and has a pair of 

 mouth-hooks directed backwards, by which it can lever 

 its way up the nostril passages and into the cavities in 

 the upper jawbone, where, by setting up irritation, they 

 cause the formation of the secretions that they feed on. 

 The full-grown maggot is nearly an inch long, whitish 

 and striped, and when about to pupate, it works its way 

 down the nasal passage again, and is sneezed out on to the 



