LIFE history OF CATTLE TICK. 21 
it would be necessary to remove cattle from pastures in which tick 
eggs might be to avoid danger of infestation by seed ticks. Possibly 
a more feasible application would he the collection of the necessary 
data from many localities by the State 1 entomologists and the publi- 
cation of predictions based upon them from time to time. 
A seasonal arrangement of our data for L905 and L906 shows the 
following: 
Eggs deposited in dune, duly, August, and up to September 15 
require from 824.3 to 840.5 degrees of accumulated effective tem- 
perat lire for hatching. 
Eggs deposited from September l6-30,in October, and in later fall 
and winter months, require an accumulated effective temperature of 
from 837.6 to 1,510.8 degrees. 
Eggs deposited in April and May require from 9S1.6 to 1,139.1 
degrees. 
Naturally an arrangement by months as above must be defective, 
since no two seasons are exactly alike. The only accurate method 
must be based upon a knowledge of the temperatures that are accu- 
mulating in any particular season. 
EFFECT OF HEAT AND COLD ON EGGS. 
In experiments to determine the effects of heat upon eggs a con- 
tinuous temperature of 100° was maintained by means of an incu- 
bator. The period of application of heat was 15 days. In one series 
no moisture was provided, and in this case no hatching took place. 
In another series in which abundant moisture was furnished, hatch- 
ing took place and the incubation period was reduced to 15 days. 
It will thus be seen that a moist atmosphere is essential to the hatch- 
ing of eggs under a constant high temperature. 
In experiments relating to the effects of low temperatures on eggs, 
by means of a refrigerator a mean temperature of about 45° was 
maintained, with a minimum of 32° and a maximum of 65°. The 
eggs were kept in pill boxes with gauze tops to allow free circula- 
tion, except during the period of refrigeration, when the ordinary 
covered pill boxes were used. The eggs from about 20 engorged ticks, 
collected on July 26, were placed in the refrigerator on August 4 
and remained for 30 days. Hatching began on September 23, and 
about 60 per cent of the eggs were viable. 
In the case just referred to, the normal period of incubation was 
increased, as the result of refrigeration, by 8 days. In a long series 
of similar experiments, however, in which the period of refrigera- 
tion ranged from 1 to 21 days, the period of incubation was not 
appreciably lengthened and the normal percentage of hatching took 
place. 
