REPRODUCTIVE PERIOD. 71 



from the latter part of September to and including November the 

 period varies from 12 to 53 days. A case occurred in the autumn of 

 1907 where it required 53 days for a single individual to reach ma- 

 turity. This individual continued to live up to the 10th of December, 

 when all experiments were closed. The average period from birth to 

 reproduction for the summer months, early spring, and early fall is 

 9, 22, and 19 days respectively. The average for the entire year, or 

 for the period in which the species breeds, parthenogenetically, for 

 Richmond and La Fayette, Ind., is 16.6 days. In arriving at these 

 averages, all individuals of the generation experiments for 1907, 1908, 

 and 1909 were considered. 



Mr. Urbahns found that at Dallas, Tex., the period varied from 

 7 to 12 days from birth to reproduction, from March to the middle of 

 May; from 6 to 14 days from the middle of May until the last week in 

 September, and from 9 to 11 days from the last week of September to 

 November 3 . The average number of days from birth to reproduction 

 for each of these periods is 9.6, 7.4, and 9.7 days, respectively. Mr. 

 Urbahns reared a number through December up to the middle of 

 January. During this period the time between birth and reproduc- 

 tion was very much greater, varying from 18 to 25 days, with an 

 average of 20.5 days. The average, beginning with April and con- 

 tinuing until November 3, is 8.9 days. From the foregoing data it 

 will be seen that under favorable conditions Toxoptera breeds much 

 more rapidly in the South than in the North. All of the reproduction 

 experiments upon which these figures are based were carried on out 

 of doors, but the insects were protected from the hot rays of the sun in 

 the summer. 



REPRODUCTIVE PERIOD. 



The period of reproduction covers a greater average length of time 

 in spring and fall than during summer, being greatest in the spring, 

 even though the maximum period of reproduction for a single female 

 is practically the same for the three periods. 



In computing these averages each individual of all the lines of con- 

 tinuous generations was considered, even though they reproduced for 

 a single day only and then died or disappeared from some unknown 

 cause; hence the averages are lower than they would be had these 

 latter individuals not been considered. From this data it will be 

 seen that both the maximum and the average periods are the great- 

 est in the North, where the insect is able to breed continuously in 

 unprotected places throughout the summer. 



At Richmond and La Fayette, Ind., the maximum period of repro- 

 duction for individuals born from March to the middle of June is 45 

 days, the minimum 1 day, and the average 18 days; the maximum 

 for individuals born from the middle of June to the middle of August 



