12 



THE EED SPIDER ON COTTON. 



cost of 100 gallons of each. If one of these were to be used in 

 preference to all others it should undoubtedly be potassium sulphid. 

 This insecticide commends itself from every standpoint — cheapness, 

 simplicity of preparation, continued readiness for use, ability to kill 

 quickly, and safety of foliage. Altogether it seems to be an ideal 

 red-spider spray. It was found that 100 gallons, when applied as a 

 misty spray, about sufficed to treat an acre of average-sized cotton. 



Table II. — Some satisfactory sprays for the red spider. 



Sprav 

 No." 



I 

 II 



III 

 IV 

 V 



VI 



Formula and items. 



Potassium sulphid, 3 pounds, at 25 cents 



Water, 100 gallons. 



Flowers of sulphur, 15 pounds, at 4 cents] ( . 



Fresh lime, 20 pounds, at 4 cents /boiled'! . 



Water, 100 gallons ) [ 



Miscible oil, 5 gallons, at $1 



Water to make 100 gallons (1 to 20). 



$0.00 

 .80 



Potassium permanganate, Ifii pounds, at 50 cents 



Water to make 100 gallons (2"per cent solution). 



Miscible oil, 2§ gallons, at $1 $2. 50 



Black-leaf tobacco extract, 40%, J gallon, at $1.25 per pound 2. 00 



Flowers of sulphur, 28 pounds, at 4 cents $1. 12 



Soft soap, 14 ounces, at 40 cents per pound 35 



Water to make 100 gallons. 



Total 

 cost. 



$0.75 



1.40 

 5.00 



8.25 



1.50 



Per cent 

 killed. 



100 

 100 



100 



sum:mary. 



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 CO round, 

 colorless eggs, which hatch in summertime in about four days. 



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

 in two daj'^s to the primarj?^ nymph. 



This first nymphal stage (and all later stagas) 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 full.y 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 15 generations 

 in an average 3^ear in that localit3\ 



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 July) several acres of a field may become 

 badly damaged. 



