UNCLASSIFIED PESTS 353 



the mite is provided with four pairs of legs ; it is nearly 

 sV hich in length. It feeds actively and in about three 

 days molts again. The third stage nymph averages ^o i^^ch in 

 length. In this stage the mite develops the habit of spinning 

 a web. In about three days the mite molts for the third and 

 last time and assumes the adult condition. It is thus seen that 

 in the course of its development the mite passes through three 

 immature stages and reaches maturity in nine or ten days after 

 hatching from the es:g. In about three days the females 

 begin egg-laying. The number of generations produced an- 

 nually varies with the length of the season and with the con- 

 dition of temperature and moisture. When the weather is 

 dry and hot the time elapsing from the laying of the egg to the 

 time at which the mature female lays her first egg may be only 

 nine or ten days, but in the cooler weather of the spring and 

 autumn this period may be lengthened to over a month. Ob- 

 servations of the mite on cotton in South Carolina have shown 

 that breeding from the first egg laid by the females of each 

 generation as many as seventeen generations may be produced 

 annually but owing to the fact that the mites may continue 

 egg-laying for a month or more several of the later generations 

 must be only partial. Under greenhouse conditions breeding 

 may be continuous throughout the year. 



The injury caused to most plants by the red-spider is indi- 

 cated by small light-colored spots on the leaves, the result of 

 the death of the plant cells around the feeding punctures. When 

 numerous these spots coalesce and the leaves take on a whitish 

 appearance. Injured plants usually become paler or take on a 

 reddish cast and finally the leaves may shrivel and die. 



Control. 



In the greenhouse the red-spider may be held in check by 

 watering the plants frequently with a nozzle that gives a stiff 

 s] ray without delivering enough w^ater to drench the beds. 

 2 a 



