THE EED SPIDER ON COTTON. 5 



Table II indicates the duration of. and the period covered by, each 

 of the IC) generations for 191"2 as Avell as for the 1911-12 wintering 

 generation. 



Table II. — Development of yeiKiitlioiin of tJic red xjiidcr on cotton in 1912. 



' This is the wintering generation and should hardly be counted with the 1912 broods. 

 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 day 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 

 upon the leaf. The eggs are usually clustered rather closely and 

 rarely occupy an area greater in size than that of a dime. Feeding 

 continues interruptedly throughout the period of egg laying, and the 

 a fleeted area of the leaf becomes thickly dotted with the blackish- 

 green puncture marks. Meanwhile a wine-red spot has appeared on 

 the upper surface of the leaf directly over the young colony, which 

 spreads as the colony increases and may finally color the entire leaf. 

 As the eggs hatch the larva' remain close to the place of their birth. 

 The mites seem to be decidedly gregarious. In a young colony 

 there is usually little web formed, but where the spiders are verv 

 abundant the web may become quite conspicuous. It doubtless 

 aft'ords some protection from adver.se weather conditions, as well as 

 agaiiLst hostile intruders, since upon several occasions predaceou.s 



