Biology of 1. ricinus 301 



Adults take about 10 days to harden and darken, remaining very quiet 

 until this is accomplished and they are ready to attack a host (Wheler, 

 xii. 1899). According to Kossel and his colleagues (1903, p. 40) the 

 males emerge prior to the females. 



Longevity. 



The duration of life of ticks, removed from the host, varies greatly 

 according to the conditions under which they are kept. They are soon 

 killed by desiccation: thus Wheler, (xii. 1899) found all stages did not 

 survive over two to three days when placed in a dry empty bottle 

 They resist cold : Wheler (1899, p. 7) found that females survived after 

 exposure to " several degrees of frost " ; and Kossel and his colleagues 

 (1903, p. 43) convinced themselves that all stages survived exposure to 

 the rigours of a German winter. The fact that the different stages 

 hibernate accounts for the occasional occurrence of piroplasmosis amongst 

 stall-fed cattle in winter, for bedding containing pathogenic ticks may 

 at times be brought into cattle-sheds from tick-infested places. All 

 stages may survive unfed for a considerable length of time in bottles 

 containing dampened moss, filter paper, sand, or earth, as shown by the 

 following records. 



Larvae (unfed) hatched 4. vin. 1898 were alive and active on 7. vi. 1899 : 

 10J months (Wheler 1899, p. 50). 

 survived 19 months (Wheler, 1902). 



„ for months (Kossel, Schiitz, Weber and Miessner, 1903, p. 40). 



Nymphs (unfed) survived 5 to 7 months (Nuttall, 1905, v. supra). 



18 „ (Wheler, 1902). 



Adults (unfed) survived 15 to 27 months, having been derived from nymphs which 

 took 12 months to undergo metamorphosis into adults (Wheler, 1902). 

 partially-fed females, taken from a dog, survived one to three months, and 

 two males placed in a vessel with cherries, died in 50 days (Galli-Valerio, 

 1908, p. 611). 



The time required to complete the Life-cycle. 



Wheler (xii. 1899) says that this species will, in fine, warm seasons, 

 probably pass through at least two stages of its life in one year, but 

 that in cold weather and when there is delay in finding a host, one 

 stage may occupy a whole season. The term of its whole existence may, 

 therefore, vary from l£ to 3 years, and will in the majority of instances 



