DISEASES OF SHEEP 527 



that it is almost if not wholly dependent upon the blood for its 

 nourishment. The bite at the time of its infliction is not painful, 

 but afterward it becomes reddened and itches even more than that 

 inflicted by the mosquito. - 



The tick does not reproduce rapidly like the sheep scab mite. 

 Only one egg is laid at a time and not more than eight or nine are 

 produced during the lifetime of the female. A number of observers 

 believe that there are only one or two. The egg is large and re- 

 sembles a seed. It has a hardened case, having a row of seven dots 

 one on each side. The special peculiarity of the eggs is the fact that 

 they contain half developed pupae at the time they are deposited. 

 The eggs are laid in the wool and a slight waxy substance secures 

 their adhesion. The insect comes out with fully developed charac- 

 ters. The length of time required for the eggs to hatch is variously 

 given at from three to four weeks. A large number of eggs taken 

 by myself from sheep, and placed in wool at body temperature re- 

 quired from 17 to 22 days to develop. 



The tick is a true parasite and can not live off the sheep more 

 than a few days. Not being able to fly they must depend upon 

 crawling to infect new stock, and this necessitates close contact, or 

 the use of very recently used pens. The tick may fall upon the 

 bedding and by chance crawl upon another animal. Their slow 

 rate of multiplication prevents them from becoming very numerous 

 except in the spring of the year. At shearing time from fifty to two 

 hundred may be found on badly affected animals. After shearing 

 the tick will migrate to the lamb because of lack of protection and 

 under such circumstances may cause considerable loss. 



The means of destroying the tick is by dipping, the same as for 

 scab. The dip used for this purpose need not be more than one- 

 third or one-half as strong as that used for scab. The preferable 

 dips are those containing crude carbolic acid or creolin. The sheep 

 or lamb need not be in the bath more than a few seconds. The 

 sheep become no wetter by continued immersion. Unlike the con- 

 dition in scab the parasites are all on the outside and readily acces- 

 sible. Sheep giving evidence of this trouble should be dipped at 

 any time if the weather is favorable. They should be dipped after 

 shearing as the quantity of dip then required is small. Both the 

 old sheep and the lambs should be dipped at the same time. While 

 one dipping will so rid the flock of ticks that they will not again 

 become very numerous during the summer, a second dipping is 

 necessary to completely eradicate them. This should take place 

 about two weeks after the first when the young will have made their 

 appearance and can be destroyed. In the winter when this treat- 

 ment is not practical the free use of Pyrethrum powder well dusted 

 into the wool will be quite effectual. 



After the destruction of the insects on the sheep, it is best to 

 put the flock in new pens until the ticks which may have been 

 dropped about the yards and pens will have died. The shorn wool 

 should also be far enough removed so that the ticks cannot crawl 



