THE RED SPIDER ON COTTON. 21 



on cotton of averat^e or low size, as the passing wagon will injure 

 large plants. 



Necessity for thorough sprayinrf. — Some dissatisfaction has been 

 experienced among certain of those who have undertaken to check 

 the ravages of the red spider by spraying. This can be understood 

 on account of the extreme care which must be exercised in order to 

 secure effective results. In the case of insects which devour the plant 

 tissue even the careless application of Paris green or lead arsenate to 

 the top of the foliage is often effective. This is explained by the fact 

 that such pests are constantly moving from leaf to leaf and will 

 eventually eat some of the poisoned tissue. Moreover, these insects 

 often eat entirely through the leaf, and hence it matters little wdiether 

 the poison falls upon one side or the other. With the red spider, 

 however, it is altogether different. A contact insecticide is absolutely 

 necessary, and, from the fact that the mite as a rule passes its entire 

 existence upon the underside of a single leaf, it becomes plainly 

 necessary in spraying to hit the entire underside of every leaf of an 

 infested plant. It is obvious, therefore, that indifferent spraying is 

 certain to yield unsatisfactory results. Furthermore, the absolute 

 necessity for a second spraying to kill the hatched eggs adds to the 

 difficulty. 



It is hoped that this discussion may impress upon the reader the 

 economy of prevention of infestation. 



SUMMARY. 



The female red spider, appearing to the naked eye like a dot of 

 reddish ink from the point of a fine pen, lays about 50 or 60 round, 

 colorless eggs, which hatch in summer time in about four days. 



The colorless, newborn spider has six legs, feeds at once, and molts 

 in two days to the primai-y nymph. 



This first nymphal stage (and all later stages) possesses eight legs, 

 and has become larger in size and darker in color. In two more days 

 (in summer) it, in turn, molts to the secondary nymph. 



The second nymphal stage lasts two days, at the end of which time, 

 after molting, the fully formed adult emerges. Mating occurs at 

 once and egg laying commences immediately afterwards. 



Thus one generation requires in summer weather in South Caro- 

 lina about 10 or 11 days. There are probably about 16 or 17 genera- 

 tions in an average year in that locality. 



The red-spider colonies live on the underside of the cotton leaves, 

 and their constant feeding causes blood-red spots to appear on the 

 tops of the leaves. The effect upon the cotton plant is that the leaves 

 drop, one by one. until usually the plant dies. 



The pest increases and spreads most rapidly in hot, dry weather 

 until (toward the end of August) several acres of a field may become 

 badly damaged. 



