The Sheep Nostril Fly. 



[JULY, 



The flies leave their shelter places in sunshiny warm weather, 

 both sexes for pairing, and afterwards the females fly towards the 

 sheep. The eg gs are somewhat curved or kidney-shaped. The 

 newly hatched maggots (Fig. 6) are very small, white and worm- 

 like, becoming longer and rounded as they grow ; they have two- 

 backwardly directed hooks at the head end, between which 

 is the mouth ; along the under surface of the abdomen are 

 transverse rows of little projections ; on the free end of the 

 last segment are the spiracles or openings of the breathing 

 tubes, below these is a lobe with spines, and on each side a little- 

 process, spines and processes playing their part in the move- 



The Sheep Nostril Fly (after Riley). 



ment of the maggot. The full-grown maggot (Figs. 4 and 5) 

 measures between three-quarters of an inch and an inch. 



Life History. — The females deposit their eggs ready to hatch,, 

 or newly-hatched maggots, at the sheep's nostril, and the maggots 

 by their mouth hooks and anal processes and spines draw and 

 push themselves up the nostrils (e), the pricking and wounding of 

 the lining mucous membrane causing the attacked sheep much 

 irritation. The larvae feed on the secretions resulting from the 

 irritation caused by their presence and their prickings, and 

 become mature in the frontal (k) and maxillary sinuses of the 

 sheep. Occasionally maggots, wandering into the recesses of 

 the turbinated bones (gg), become with their increase in size im- 

 prisoned there, and undergo degeneration. Ultimately, the full 

 grown larvat returning to the passages are sneezed out on to 

 the ground, where a little below the surface, or under a clod, or 

 sheltered in a tuft of grass,the pupation stage (Fig. 3)is passed, the- 



