426 
Biologn of Ixodidae 
The time the tick remains upon the host: larvae feed for 2-8 days 
(7 experiments)2 or 3-7 days^; nymphs feed for 4-9 days (7 experi- 
ments)i or 3-7 days^; females feed for 8-14 days either on the ox 
or guinea-pig (5 experiments)’ or 5-15 days^. Metamorphosis from 
egg to larva lasts 15-41 days in Texas, 34-51 days in Montana’ 
or 14-25 days-; from larva to nymph it lasts 6-21 days (8 experi¬ 
ments)’ or 13-20 days^; from nymph to adult it lasts a minimum 
of 12 days to a maximum of 170 days (8 experiments)’ or 20-40 
days^. Ovi'position, reckoned from the time the replete female 
abandons the host, begins after 6-13 days in warm weather and 
after 41 days when it is cool’ or it commences after 8-14 days^; 
the process lasts 30 days’ or 8-20 days^, the female dying a few' 
days later’; the number of eggs laid is usually about 4000’ or 
2500-3000^. Copulation occurs on the host’, the S seeking the 
9 some 4-8 days after the sexes have attached themselves; 
the remains upon the host after the $ has dropped ofi, and 
the ^ may copulate with several 9s’. Longevity of unfed ticks: 
larvae usually die in 30 days, but a few survive up to 117 days; 
nymphs live for over 300 days; adults captured on vegetation in 
the spring, survived unfed for 413 days’. Season : adults which 
emerged in July to October became active and fed in January and 
March, this corresponding with their behaviour in nature where 
they remain torpid for 4-5 months after emergence^. The unfed 
nymphs and adxdts hibernate, find hosts in March to July (when 
they attack man) in Montana; the females which feed in spring 
lay eggs which lead to adults in September. Nymphs are found 
on small wild animals in March to July inclusive, they hibernate 
as unfed adults. The adults are found on large wild and domesti¬ 
cated animals and on man, but the immature stages rarely if ever 
occur on other than small animals. A very full list of the natural 
hosts of D. venustus is given by Hunter and Bishopp [q.v. pp. 28-29). 
The life-cycle is usually completed in 2 years, but it may require 
3 years for its completion’. 
According to the investigations of Ricketts on Rocky Mountain 
Spotted Fever, D. venustus transmits the virus of the disease as 
a nymph if it has fed upon an infected host (man, monkey, guinea- 
pig, etc.) in the larval stage; when infected as a nymph, the tick is 
infective as an adult, and larvae, the progeny of an infected female 
tick, are also infective.] 
1 Hunter and Bishop 2 ). 
^ Maver. 
