THE EED SPIDER ON COTTON. 



PARTHENOGENESIS. 



Experiments conducted with unmated female red spiders clearly 

 proved that they are normally capable of laying eggs, which in turn 

 hatch and develop into mature individuals. No tests, however, have 

 been successfully conducted' to determine the sexual fertility of the 

 latter. 



GENERATIONS. 



The season of 1911 at Batesburg, S. C, was one of unusual drought 

 and heat and there were about 17 generations between March 11 and 

 November 5. The time required for a single generation varied from 

 35 days in March and early April to 10 days throughout most of 

 June, July, and August, and to 25 days in the greater portion of 

 October and early November. The following table presents the 

 duration of each stage of each of the 17 generations : 



Table I. — Development of generations of the cotton ted spider. 



Gener- 

 ation. 



1. 

 2. 

 3 

 4. 

 5 

 6 

 7 

 8 

 9 

 10 

 11 

 12 

 13 

 14 

 15 

 16 

 17 



Period covered by gerneration. 



Mar. 11 to Apr. 14.. 

 Apr. 15 to Apr. 29. . 

 Apr. 30 to May 13.. 

 May 14 to May 25.. 

 May 2(j to June 6... 

 Juno 7 to June 17., 

 June IS to June 27. 

 June28lo July 7... 

 JulvH to July 18... 

 July 19 to July 28.. 

 July 29 to Aug. 7. . 

 Aug. 8 to Aug. 17.. 

 Aug. 18 to Aug. 29. 

 Aug. 30 to Sept. 9. 

 Sept. 10 to Sept. 24 

 Sept. 25 to Oct. 10. 

 Oct. 11 to Nov. 4.. 



Average 



Incuba- 

 tion 

 period. 



Days. 

 13 

 6 

 6 

 5 

 5 



4.C 

 4 

 4 

 4 

 4 

 4 

 4 

 5 

 5 

 5 

 6 

 9 



Larval 

 period. 



Days. 

 9 

 3 

 3 

 3 

 3 



2.5 

 2 

 2 



2.5 

 2 

 2 

 2 



2.5 

 2 



3.5 

 3 

 6 



Nymph 



(1) 

 period. 



Days. 

 

 3 

 3 

 2 

 2 

 2 

 2 

 2 

 2. 

 2 

 2 

 2 

 2 

 2 

 3 

 3 

 5 



Nymph 



(2) 

 period. 



Days. 



7 



3 



2 



2 



2 



2 



2 



2 



2 



2 



2 



2 



2.5 



2 



3.5 



4 



5 



2.8 



Ovipo- 



sition to 



adult. 



Days. 



14 



RELATION OF AVEATHER TO BREEDING ACTIVITIES. 



The influence of the weather on breeding activity is very notice- 

 able. Hot, dry conditions greatly favor and hasten development, 

 while cool, wet weather correspondingly retards it. A female laying 

 normally about G or 7 eggs per da}'^ will often upon the occurrence 

 of a very hot day, suddenly increase the number to 15 or even more 

 eggs per day, or upon a chilly day may drop as suddenly to 1 or 2 

 eggs. It is easy then to understand the remarkable rate at which 

 this pest increases during times of unusual drought. 



OBSERVATIONS ON HABITS. 



In establishing herself upon cotton the female selects a concave 

 area between the under veins of the leaf and begins at once to deposit 

 eggs. These may be attached to the fibrils of the web slightly above 

 the surface, or, as seems most often the case, they are placed directly 



