1(54 
Biology of Dermacentor 
half of February they became much more numerous. This was during 
a warm period. The last specimens taken were collected on April 4. 
Examinations of hosts made on April 27 and subsequent dates failed to 
reveal the presence of any specimens of this species. No ticks were 
found on hosts in this locality on December 23, 1912, and during 
previous examinations in the fall, but on the next observation, which 
was made January 9, 1913, 3 </, 8 $ (mostly unengorged, one fully 
engorged), and 25 nymphs were found. Thus it would appear that in 
this locality few ticks got on the hosts during the winter of 1912-13 
until about December 10. 
The latest date on which we have a record of the collection of this 
tick is May 31. In this case a single, slightly engorged, female was 
taken on a horse at Pony, Montana, at an altitude of about 5500 feet. 
As previously stated, nymphs and adults were taken near Darby, Montana, 
on May 14, and a single female on May 19, 1910. These were all taken 
from hosts killed at between 5000 and 7000 feet altitude. 
Nymphs are found on the hosts throughout practically the entire 
period when adults are present. Of course their appearance shortly 
precedes that of the adults and the latter are present some days after 
the last nymphs moult. March and April are the months when the 
ticks in both the nymphal and adult stages are usually most 
abundant. 
At Dallas, Texas, larvae hatched from eggs deposited by females 
dropped from hosts in the winter and spring, exhibited a decided 
disinclination to attach themselves to hosts until the following fall and 
winter. In the northern part of the range of this tick the eggs have 
been found not. to hatch until the late summer and early fall 1 . Hence 
we may conclude that in the warmer portions of the country where 
this tick occurs the larvae may hatch during the summer but remain 
inactive (as observed at Dallas) until cool weather. In the colder 
portions of its range the hatching does not take place (as observed by 
Mr W. V. King, in the Bitter Root Valley, Montana) until late summer 
or fall. In either case the larvae attach themselves to hosts when 
favourable weather prevails during the fall, winter or spring. 
1 From a statementby Mr W. J. Hays ( Amer. Nat. Yol. ii. (x.), p. 559, 1868) we learn 
that ticks collected in New York City on April 13 began depositing eggs on May 1 and 
these eggs hatched on July 3. Dr Gordon Hewitt (Rept. Dominion Ent. for 1911, p. 225) 
states that egg laying began (presumably in Ottawa, Canada) at the end of April and 
hatching began early in July. Both of these records were probably made indoors although 
this point is not stated. 
