THE CAMPHOR THRIPS. 9 



Hence some difficulty was encountered in keeping the thrips for 

 long periods, and many cultures were started in order to complete 

 the desired number. 



DURATION OF LIFE CYCLE. 



As observed by the writers, the life cycle of the camphor thrips 

 varied considerably according to the season of the year. In August, 

 1921, 375 eggs required an average of 6 days in which to hatch, and 

 the combined larval and pupal stages for 57 individuals averaged 

 12.65 days, giving an average of 18.65 days from egg to adult. The 

 average life of 20 adults during the summer months was 98 days, 

 and they laid an average of 463.7 eggs. 



During this period (August, 1921) the maximum temperature at 

 the laboratory in Orlando, Fla., ranged from 88° to 100° F., with a 

 mean maximum of 94° and a mean minimum of 71.2°. The total 

 precipitation was 4.13 inches. 



The winter-season breeding work was carried on during November 

 and December, 1921, and January, 1922. During this period 97 eggs 

 required an average of 13.6 days in which to hatch and the combined 

 larval and pupal stages for 40 individuals averaged 24.7 days, making 

 a total of 38.3 days from egg to adult. The average life of 20 adults 

 was 82.8 days, and the average number of eggs laid was 307. The 

 temperatures during this period were as follows: In November, 1921, 

 the maximum temperatures ranged from 71° to 86°, with a mean of 

 79.5°, and the mean minimum temperature was 53.9°. The total 

 precipitation was 3.62 inches. For December the maximum tem- 

 peratures ranged from 65° to 80°, with a mean of 74.3°, while the 

 mean minimum was 48.6° and the total precipitation was 2.23 

 inches. For January, 1922, the maximum temperatures ranged 

 from 61° to 84°, with a mean of 77.3°. The mean minimum was 

 50.1° and the total precipitation was 0.52 inch. 



Allowing for the preoviposition period, which averaged 3.2 days 

 in summer and 7.4 days in winter, the average period of development 

 in summer from egg to egg would be 21.85 days and in winter 45.7 

 days. Judging from these figures, the maximum number of genera- 

 tions of the camphor thrips per year would be about 12. 



THE EGG. 



INCUBATION PERIOD. 



The time required for development of the egg varies considerably 

 even at the same time of the year. During the warmer weather this 

 period ranges from 5 to 9 days, with an average of 6 days, while in 

 the cooler weather of winter it ranges from 10 to 16 days, with an 

 average of 13.6 days. Thus the egg requires more than twice as long 

 to develop during the cooler part of the year. A variation of 2 or 3 

 days was also observed in the development of eggs laid on the same 

 day by the same female. The percentage of eggs hatching seems to 

 be very high, averaging 98.2 per cent in summer and 86 per cent in 

 winter. The detailed records on incubation of the egg are given in 

 Table 1. 



69578°— 24 2 



