92 BULLETIN 416, U. S. DEPARTMENT OF AGRICULTURE. 
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 sprmg 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 all our continuous records of the past 
four years and undoubtedly represent the normal sequence of broods 
in South Carolina. 
TaBLeE II1.—Seasonal sequence of the 17 annual red-spider broods at Batesburg, S. C. 
| | | 
Com- Com- 
Brood. | Bees Hones Duration. Brood. Meee: ed Duration. 
| | 
| | | 
| Days Darys 
Leh eee Mar. 31 | Apr. 22 22 iD ees Aug. 3] Aug. 12 10.7 
ee Apr. 23| May 5 13 122-0232) Ang. 13 Anes 23 FA? 
oS hs May 6 {| May 17 2 1p Reese ug. 24| Sept. 3 | 11 
7 Sa Se May 18}; May 29 12 Asc Sept. 4] Sept. 15 13 
Sees May 30/ June 9 LA A  ess2 Sept. 16 | Sept. 30 15 
GME June 10 | June 20 AO ait Geer Ochs salOct 22 22 
Te ee June 21 | July 1 LOS CAS Taoe eta Oct. 23} Mar. 30 159 
Saou July. 2| July 11 10.7 
Eee = July 12 | July 22 10.7 LhotalSa|peee os 365 
1OSs se July 23 | Aug. 2 LO } 
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 life history and biological statistics were secured through 
the use of a special type of rearing cell which is attached directly 
to the leaf of the living 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 within the cell are nearly normal. It was found that in 
