THE KED SPIDER ON COTTOlSr. 7 



minimum, and lie fomicl that this fluctuation was induced largely by 

 temperature and nutrition conditions. 



In the course of the five seasons' observations at Batesburg many 

 colonies have been reared under control. From a series of 90 such 

 broods the summaries given in Table I are derived : 



Table I. — Records of oviposition of the red spider. 



Largest brood 110 



Average for 20 largest broods 68. 01 



Average for 10 largest broods 80. 10 



High daily depositions 12, 1 13,2 14 3 15 4 iq-. 17 5 jg 1 



Maximum dailj^ oviposition ; 19 



Total eggs from 38 broods 1, 893 



Total egg-laying days (38 broods) 320 



Average eggs per day per female 5. 92 



Average ovipositing days per female 14 



Maximum ovipositing days per female. 36 



From these rearmgs it follows that for South Carolina the female 

 under proper conditions will produce a brood of from 75 to 110, 

 probably averagmg about 85, and that the eggs are deposited usually 

 in from 10 to 12 days at the rate of from 8 to 14 per day. 



Incubation period. — The duration of the incubation period varies 

 largely with the temperature m the different localities. Perkms 

 (1897) found that 7 days were required in Vermont for this period. 

 Ewmg (1914) states that an average of 5.5 days were consumed at 

 Corvalhs, Oreg., between deposition and hatching. In Georgia from 

 3 to 4 days were required for incubation, according to Worsham. In 

 a series of 71 breeding-cell tests (each cell contaming the progeny of 



I female) the average duration of this period at Batesburg was found 

 to be 3.93 days during May, June, July, August, and September. 



In hatchmg, the shell sphts more or less completely around and the 

 larva easily extricates itself. During severe occurrences of infestation 

 the leaves of the host plant may be seen thickly covered with the 

 bleached and empty eggshells, which disclose the cause of death of 

 leaves long after the disappearance of the pest has occurred. 



The effect of temperature upon the incubation of the red-spider 

 egg is \'ery marked. In midsummer, at Batesburg, with mean daily 

 temperatures between 80° and 90° F., incubation rarely requires 

 more than 4 days. One rearing beginning March 12 consumed 15 

 (hiys for the hatching period. Eggs, in one case, deposited November 

 16 hatched in 23 days. During December, January, and February 

 eggs may remain dormant for from 1 to 3 montlis, hatching with the 

 advent of suflicicntly mild weather. The relationship between mean 

 temperatures and the length of the egg period is shown in Table 



II and figure 2. The eggs of a colony are usually clustered upon 



• ■; caws. 1 5 cases. a 4 cases. ■» 2 cases. '■ 1 case. 



