THE TICKS 



149 



thirty-six days for October. The maximum period observed was forty- 

 nine days for October, the minimum four days for July. 



The longevity period is stated to depend on individual vitality, 

 humidity, and temperature. It was noted, especially in eggs laid during 

 the winter, that some larvse do not have sufficient vitality to disengage 

 themselves from the eggshell and die partly inclosed within it; also that 

 others die very soon after emerging. Cold, it is stated, prolongs longev- 

 ity because of the fact that the tick remains quiescent with resulting 

 conservation of body fluids and nourishment. The fact that the larvae 

 respond negatively to light is an additional factor promoting longevity. 

 In places exposed to the sun they collect on the under side of leaves and 

 other vegetation, thus protecting themselves from loss of body moisture 

 through the direct heat of the sun. In observations made it was deter- 

 mined that the average maximum longevity for larvae hatched from a 

 number of lots of eggs in July was thirty-eight and six-tenths days. 

 From eggs hatched in October the average maximum period was one 

 hundred and sixty-seven and four-tenths days. The shortest period 

 was four days for larvae hatched in July, the longest two hundred and 

 thirty-four days for larvae hatched in October. 



The following summaiy is given of the data on the nonparasitic 

 period : 



Total Time from Dropping of Female until all Resulting Larvoe are Dead 



The Parasitic Development. — The parasitic development has three 

 stages, the larval, the nymphal, and the adult. In the experiments car- 



