Biology of H. leacki 541 



may remain upon the host for many weeks (according to Lounsbiiry). 

 The temperature of the air within the limits observed (9-23° C.) appears 

 to exert little or no influence upon the time the tick remains upon the 

 host, the warmth emanating from the latter being doubtless sufficient 

 to keep the ticks active. The time required for metamorphosis^ is 

 influenced by temperature, thus the larvae hatch after 26-37 days at 

 20" C, in 58 to 80 days at 12-13° C; the nymphs emerge, as a rule, 

 after 30 to 40 days; adults emerge after 15-16 days at 24-26° C. 

 whereas they may only emerge after 42-70 days at 14° C. The longevity 

 of the unfed tick is considerable when the conditions are favourable ; in 

 small corked bottles some larvae were still active after 399 days, the 

 nymphs after 61 days and the adults after about 210 days when 

 maintained at room temperature in semi-darkness and all stages fed 

 upon their hosts after these periods. When males and females are 

 simultaneously placed upon the host they scatter, but the sexes are 

 found attached in close proximity to each other after 2-3 days. Copu- 

 lation must take place upon the host, though it has never been actually 

 observed. (Lounsbury has seen males, which he had marked, detach 

 themselves and reattach themselves close to females ; a male may mate 

 with more than one female.) I find that the males do not seek the 

 females as do Ixodes when the sexes have been removed from the host. 

 The time which elapses before oviposition commences, after the replete 

 female adandons the host, is markedly influenced by temperature ; thus, 

 when females were placed at 23° C. they began to lay after 3-5 days, at 

 16-21° C. after 14-18 days, at lower temperatures after 24, 47 to 60 days. 

 Whereas an occasional female dies as soon as oviposition has ended, 

 others may survive for a few days or, in exceptional cases, for a month 

 The female lays from 2400 to 4800 eggs. H. lecwhi begins to abandon 

 its host on the approach of death in a manner that neither Lounsbury 

 nor myself has observed in other ticks. 



In nature, this tick may doubtless run twice through its life cycle in 

 a year. By the use of an incubator, as first shown by Lounsbury, this 

 author succeeded in raising three generations in a year. Taking 

 average figures from my protocols of ticks raised under favourable 

 conditions, the cycle may be completed in 123 days, as follows: 



' See reference to Lounsbury's observations on p. 536. 



N. I. ^5 



