2^ 



BULLETIN 416, U. s. DEPAR'rMi;J^J T OJ?' AaKlUULl Ui{E. 



successive generations in seven months, each requiring about three 

 weeks for completion. 



At Batesburg the average time required throughout the active 

 season for the completion of a generation is 10.7 days. Since there 

 are normally about 180 active days per season at that locality, it fol- 

 lows that there should be approximately 17 successive broods in 

 South Carolina. This estimate is borne out further by the actual 

 observations in the field. 



In 1911 the wintering brood (eggs of the preceding fall and winter) 

 reached maturity about March 11; the 1911-12 wintering individ- 

 uals matured about April 17; March 25 marked the arrival of the 

 1913 initial brood of adults; and in 1914 the wintering generation 

 again completed its development about March 25. The average date 

 of appearance of the first spring brood at Batesburg is computed 

 from the foregoing records to be March 31. The time required for a 

 single generation varied from 170 days during the winter of 1911-12, 

 and 35 days in March and early April, to 10 days throughout the 

 summer. The generations, as indicated in Table III and figure 6, are 

 the composite averages of aU our continuous records of the past 

 four years and undoubtedly represent the normal sequence of broods 

 in South Carolina. 



Table III. — Seasonal sequence of the 17 annual red-spider broods at Batesburg, S. C. 



Brood. 



Com- 

 mence- 

 meat. 



Com- 

 pletion. 



Duration. 



Brood. 



Com- 

 mence- 

 ment. 



pSn. !>--«-• 



1 



2 



3 



4 



5 



6 



7 



8 



9 



10 



Mar. 31 

 Apr. 23 

 May 6 

 May 18 

 May 30 

 June 10 

 June 21 

 Julv 2 

 July 12 

 July 23 



Apr. 22 

 May 5 

 May 17 

 May 29 

 June 9 

 June 20 

 July 1 

 July 11 

 July 22 

 Aug. 2 



Days. 

 22 

 13 

 12 

 12 

 11 



10.7 

 10.7 

 10.7 

 10.7 

 10.7 



11 



12 



13 



14 



15 



16 



17 



Aug. 3 

 Aug. 13 

 Aug. 24 

 Sept. 4 

 Sept. 16 

 Oct. 1 

 Oct. 23 



Total.. 



Aug. 12 

 Aug. 23 

 Sept. 3 

 Sept. 1.5 

 Sept. 30 

 Oct. 22 

 Mar. 30 



Days. 

 10.7 

 10.7 

 11 

 13 

 15 

 22 

 159 





365 









In sheltered locations winter development may continue sufficiently 

 long to result in the maturing of one or more extra generations. 

 While instances of this are comparatively rare, they are of con- 

 siderable biologic and economic importance. 



Rearing experiments. — Practically all of our experimental data 

 covering fife history and biological statistics were secured through 

 the use of a special type of rearing ceU which is attached directly 

 to the leaf of the Hving plant (fig. 7). 



The individuals to be reared or experimented with are carefully 

 introduced into these cells by means of the finest camel's-hair brushes. 

 The felt confining pad permits the free passage of air, so that the 

 conditions wdthin the cell are nearly normal. It was found that in 



