38 



BULLETlISr 351, U. S. DEPARTMENT OF AGRICULTUEE. 



at 8.45 a. m., at which time the larva resumed its migration. At 9.30 a. m. the temper- 

 ature was 80° P., at 10 a. m. 86° F., and at 11 a. m. 88° F., from which hour it dropped 

 to 84° F. at noon, when the experiment was terminated by the death of the larva. 



Ordinarily larvse start migrating whon the temperature readies 

 70° F., and the rate of travel increases in nearly the same ratio as the 

 increase in temperature above 70° F. Larvse, if unattached, become 

 motionless when the temperatin-e falls below 72° F. The female 



\-' SECOND 

 N/GHT 



Fig . 12 . — Tracing of the total t wigward migration of a female larva of the terrapin scale . 

 Total distance traveled, 322.5 cm. (Original.) 



Reduced Stimes. 



under observation started migration August 30 at 2.40 p. m,, and 

 died September 1 at 12 noon, having lived 2 hours and 40 minutes 

 less than 3 days, and having traveled over smooth paper a distance 

 of 322.5 cm. (10^ feet). (Fig. 12.) This was undoubtedly farther than 

 the average specimen is able to travel upon its host plant. There is 

 therefore very little chance of the larvse crawling to adjacent trees unless 

 the limhs are in contact. 



A second female larva (Table XXV), captured August 26, during 

 the first day of migration, was placed upon wrapping paper at 2.25 



