332 APPLIED ENTOMOLOGY 



during this period being nourished by the secretions from glands in the 

 body of the parent. When the development of the larva has been nearly 

 completed, it leaves the parent and is then covered by a soft, white 

 membrane which, after some hours, turns brown and hard and becomes a 

 puparium within which the animal pupates for a period of from 19 to 

 24 days after which the adult emerges. After about 10 to 14 days more, 

 their first pupae appear. A" pupa is produced by a female every 7 or 8 

 days, 12 to 15 being about the usual number in all per individual. 



Control. — The most widespread method for controlling these insects 

 is by dipping the sheep in some material which will kill the ticks. Some of 

 the dips used for this purpose are coal-tar-creosote, cresol, nicotine and 

 lime-sulfur-arsenic. Selection of the best dip for the purpose must 

 be determined by the availability of soft water, ease of obtaining the 

 materials and other local factors. In general, two dippings are necessary 

 and, if this is done during the early fall, these should be 24 days apart. 

 Where shearing is done in the spring, the dipping should be in July and 

 August unless the lambs become thickly infested soon after shearing, in 

 which case dipping should be as soon as the shear cuts heal. Many 

 details connected with dipping make it necessary to become thoroughly 

 acquainted with the process before treatment is actually attempted, 

 if the best results are desired. 



