54 REPORT ON INJURIOUS INSECTS FOR 1907. 



entrance into the spinal canal. Eventually they reach the skin as before 

 (Ruser and others). 



Which of these possibilities comes nearest to what really takes 

 place during the normal life-history of the larva cannot be decided in 

 the existing state of our knowledge. It is necessary to point out that 

 this important question can only be ascertained by means of prolonged 

 and carefully conducted experiments made with the cattle themselves. 



How long the insect spends in the larval state is at present unknown. 

 The fact that the flies themselves are found during the summer, while 

 the small larvae have been found in the tissues of oxen during the 

 winter months by Koorevaar, Koch, and the other observers quoted, 

 seems to indicate that, during the early part of the larval history, 

 growth is extremely slow, though the larvae may migrate a good deal in 

 the tissues of their host." 



PREVENTION AND TREATMENT. 



The preventive measures which have been found effective are : 



(1) To let the cattle have plenty of shelter. 



(2) To spray the beasts with some strong smelling substance, 



such as carbolic acid, paraffin, oil of tar, etc. 



Certain breeders inform me that if this is done, say once a \veek, it 

 is an effective preventive. 



As to treatment, all that can be done is to squeeze the mature 

 bots out of the warbles and destroy them. 



THE SHEEP FLY. 



Lucilia sericata (Meigen). 

 Lucilia caesar (Linn.). 



There are two species of Sheep Fly which in appearance and habits 

 closely resemble one another. 



During the hot weather they may be observed flying about the 

 sheep, and depositing eggs in small clusters of fifteen to tw r enty in the 

 wool. 



The first eggs deposited are usually laid in the anal region of the 

 sheep, no doubt attracted by the odour of the faeces. 



In about twenty-four hours the tiny maggots hatch out, and at first 

 live in the filthy wool, but after a short time, by means of their mouth 

 hooks, they burrow into the skin. When full grown the maggots are 

 about half-an-inch in length, maturity being reached in a fortnight or 

 three weeks. They now drop to the ground and pupate. 



A single female may lay as many as five hundred eggs, and as 

 the life cycle is short, there may be a number of generations during 

 the season. 



