192 LIFE HISTORY OF NORTH AMERICAN TICKS. 
The egg (Table XC).—The minimum preoyviposition period for a 
large number of ticks observed at different times of the year was 5 
days and the maximum 14 days. This minimum preoviposition 
period was observed in a number of instances during the summer 
Fic. 16.—The American dog tick, Dermacentor variabilis: Distribution in the United States. The large 
_ dots show localities where the species has been collected in our investigation. The small dots indicate 
the probable range of the tick. (Original.) 
months, while the maximum period was recerded once in March and 
once in April, 1909. The mean temperature during the shortest 
period was 80° F. The period of oviposition varied from 14 to 29 
days with an average of 22.3 days. A tick which was collected on a 
