G. H. F. Nuttall 
429 
Summary. 
Dermacentor venvsitis is a 3-host tick; it is readily reared under 
experimental conditions. All stages were fed by ris on sheep; larvae 
and nymphs "were fed on guinea-pigs. In nature, the tick occurs on 
a great variety of hosts as has been shown by American authors. The 
Hme the tick remains upon the host: as a larva is 2-6 days, mostly 3 days 
[2-8 days^, ^]; the nymph feeds for 5-11 days, mostly 6-7 days [3-9 
days^, ; the female feeds for 5-15 days [5-15 days^, ^ or 4-10 days®; 
the male feeds for 3-4 days before he seeks the female and during this 
period may alter his position several times®]. Metamorphosis from egg 
to larva lasted 7-10 days at 32° C., 16 days at 30° C., 38 days at 22° C. 
[14-51 days ® or 36 days in summer]; from larva to nymph it lasted 
6-7 days at 30° C., 10-11 days at 24° C. [6-21 days^, 24-38 days in 
summer®]; from nymph to adult it lasted 14-15 days at 24-30° C. 
[12-170 days, minimum and maximum^ or 32 days in summer and 
84-94 days in winter®]. . Oviposition, reckoned from the day the female 
abandons the host, begins after 3-5 days at 30-32° C., after 11 days 
at 24° C. [6-41 days depending upon temperature’^]; the process lasts 
10-33 days at 24-32° C. [8-30 days^, ®] and the female may survive 
1-14 days after laying has ceased. The fertile eggs laid by one of our 
females numbered 7140 [2500-4000 are stated to be the usual number^, ®; 
Hadwen observed a female which laid 474 eggs in 24 hours, i.e. on an 
average of 1 egg every 2-3 minutes®]; two of our unfertilized females 
laid no eggs, but a third laid 3574 eggs which did not hatch. Copulation 
occurs upon the host [the process has been observed by Hadwen, the 
union lasted 33 minutes and occurs in a similar manner to what we 
have observed in Ixodes, the male appears to seek the semi-gorged 
female by preference for the purpose®]. The male remains upon the 
host for an undetermined period after the female has dropped ofi; it 
is clear that a ^ may copulate 'with several $s. Longevity: larvae 
which had fasted 67 days fed readily when placed on a guinea-pig [if 
unfed they usually die in 30 days, but they may survive up to 117 days; 
unfed nymphs may live over 300 days^]; adults, after fasting 356 days, 
readily attached themselves to a host [captured on vegetation in the 
spring, they survived unfed for 413 days; all stages may hibernate in 
nature^]. The life-cycle may be completed in 68 days under the most 
favourable conditions, judging from our laboratory experiments [the 
time required is usually 2 years and may be 3 years^]. 
The data enclosed in brackets are cited from (1) Hunter and Bishopp, (2) Maver 
and (3) Hadwen. 
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