28 INSECT* PESTS 



changes to a shiny, barrel-like pupa, from which it emerges 

 in about fourteen days as a perfect fly. 



Cleanhness is the chief preventive measure, especially 

 about the hind-quarters, as all these families of flies are 

 attracted by dirt, in which they prefer to lay their eggs. 

 Carcasses of birds and small mammals, too, if left about 

 to putrefy, instead of being buried for the use of ants 

 and beetles, will afford propagating centres for fly maggots. 

 The sheep dip is of course both remedial and preventive, 

 but its effects do not last more than three weeks or a 

 month, when it must be repeated. 



Badly infested sheep should be isolated and the maggots 

 picked out, and when they have been destroyed, the 

 places where the wool is matted or the skin broken should 

 be shorn a little and rubbed with turpentine and paraffin, 

 afterwards dusting with sulphur. Birds, notably the 

 Willow Wren and the Whitethroat, who Hve on an insect 

 diet, perform great service in catching these flies. 



The above are by no means the only pests that trouble 

 sheep, but we have not sufficient space here to take a full 

 survey of them. We have one remaining example among 

 Diptera, and that is the Tick, or False Tick, or Ked, all 

 of which names signify Melophagus ovinus, a degenerate 

 wingless relative of the house fly. It causes great irrita- 

 tion and loss of condition, and is a creature about J inch 

 long, brownish grey in colour, and has the unusual pro- 

 perty of retaining its eggs and nourishing them on as far 

 as the pupal state before they are deposited. Keds never 

 leave the sheep's wool, or soon die if separated, and after 

 shearing-time it has been noticed that they collect near 

 the neck. The dip is the best cure (arsenic and soda) 

 which must be repeated at intervals of three weeks to 

 destroy odd pupae which have come through unharmed. 



The true Sheep Tick is not an insect, but an Acarus or 

 Mite known as Ixodes ricinus, and it does not confine itself 

 to sheep, but can also be the cause of much misery to the 

 faithful coUie that rounds them up. Ticks lay their eggs 



