176 TICK RESISTANCE IN CATTLE 
few mature ticks were found on the floor. Even supposing 
that as many had dropped off as there were found on the 
animal, it would show that the cow under inspection and 
kept in a stall after a sojourn in a ticky paddock, had for 
some reason or another, not matured more than a few ticks. 
during that period. 
During the first ten days there were actually taken 
from the animal only 20 engorged ticks. During the next 
ten days the total was 341, while in the succeeding five days. 
490 were collected. In other words, during the first nine- 
teen days of stalling, 361 were obtained. There was no 
inspection on the 20th day. From the 2lst to the 25th 
day inclusive, there were eight inspections and about 150: 
more ticks were obtained during that time than during the 
whole of the preceding period. The maximum number 
was collected on the 22nd day and nearly as many on the 
23rd day. 
Schroeder states that 22 days is the normal parasitic 
period of a cattle tick in the U.S.A., the limits being 15 to 
40 days. Graybill reported that it extended from 22 to 
25 days in May and June in the southern part of the U.S.A., 
and from 25 to 34 in February and March, 7.e., during late . 
winter. The climate in the American regions referred to is 
much colder than that of Brisbane, hence the tick parasitic 
periods are likély to be longer than they are in our locality. 
Experimental work carried out in Southern Queensland 
under the direction of the senior author has shown that the 
periods average approximately 22 or 23 days from April 
to May, and 24 or 25 days in June and early July. The 
available evidence then points to the experimental animal 
having become parasitised by larval ticks at about the time 
of, or immediately after, stalling. 
Mr. Watson’s report, in our opinion, proved that the 
animal was able to mature ticks when confined in a stall. 
It also shows quite conclusively that extremely few ticks 
became engorged in spite of the cow‘s prolonged sojourn 
under natural conditions of infestation in an admittedly 
ticky paddock. 
Mr. Pound ignores the evidence of various observers 
who had had the same animals under their care (see our 
previous paper, 1918, pp. 243-3 
