CONTROL OF THE CATTLE TICK. 
(7) A difference of one week in the dates of dropping of ticks 
during late autumn (e.g., May) might result in a differ- 
ence of some months between the dates on which larvew 
would hatch out from the eggs laid by such ticks. This 
might happen also in the case of ticks dropped on the same 
date. For example, in plots laid down at West Burleigh, 
on 6th May, 1918, the ticks began to lay on the same date, 
viz., 15th May, but hatching occurred in some plots on 27th 
August, while in other plots it did not commence until 7th 
October. In spite of such differences, the various plots 
became clear between 24th October and 3rd. November. 
(8) We may say, then, that if from cattle in passing through a 
clean paddock in the coastal districts of Queensland 
engorged cattle ticks are dropped, such paddock will not 
be infective for from three to four weeks during summer 
(November to March). During the winter, the period 
would be two to three months (80 to 90 days). These 
remarks would apply also to the Northern Rivers District 
of New South Wales. 
In Toowoomba and other districts where heavy frosts commonly 
occur during winter, the cattle tick appears to be at present unable to 
‘establish itself. It must then become re-introduced. during the summer, 
when the period elapsing between the dropping of an engorged female 
and the emergence of its offspring from the eggs is about five weeks 
(minimum). 
The following additional remarks regarding the detrimental effect 
of cold and dry conditions on the non-parasitic stages of tick may be of 
interest. Our winter weather, especially the cold nights, profoundly 
influences the life cycle, causing either the death of the eges or con- 
tained larvee, or else a contiderable lengthening of certain periods, 
e.g., the time between egg-laying and the appearance of larvee hatched 
from such eges. The effect depends to a considerable extent on the 
state of development, the majority of the larvee dying within the shell, 
or whilst in the act of escaping from it. 
It was observed that in some plots all the eggs (or contained larvye) 
were killed by the cold, while in others begun at the same time, and 
influenced by the same external conditions, there was a prolonged quies- 
cence and eventually larve appeared. This factor must be. taken into 
account in any scheme of quarantine during autumn, winter, and early 
spring. Larve which hatched were commonly killed by the cold winter 
nights, even when the temperature was not quite cold enough for frost 
to be formed. There is a marked prolongation of the laying period under 
cold conditions, oviposition being. irregular, several days often 
elapsing between the periods of egg deposition. Females dropped late 
in the autumn seek shelter and live a considerable time on the ground, 
egg-laying being distributed over many days. The development of such 
egos either does not take place before death occurs, or else is retarded. 
Most of the larvee which develop in such eggs during the winter die 
before emerging; but a few inay survive, hatch ont, and infest cattle 
even during the winter and early spring. Should the hatching be 
retarded sufticiently during its early stages until warmer weather sets in, 
423 
