liELATlONSllIP OF FACroKS OF ('ONriU)L. 2'^ 



but it is p()ssil)l(> that (hey will ii;ra(liially accniiic nw increasing 

 importance llic lon^-crthc \\('(>\il icinains al)un(lanl. 



There are other factors whicli ai-e, oi- may ix'coine, of i-ela(i\-el\ 

 iz;reat importance in the lit^-ht ai:;ainst the wee\il. vSonie of tlies(> liaNc 

 ])ee!i hut sh*::htly in\(vstii:;ate(l. It is safe 1o assume that tlie factois 

 which have Ixmmi mentioned include those which haxe thus \';w |)r()\-e(l 

 to he of i::i"(^atest importance in holding- the W('e\il in check to some 

 extent. , 



'V\\v relative \'alue of tlu\s(^ factors is c(M"tain to chanu-e suddenly, 

 and when one assumes a position of j)re(lominant iidluence the others 

 must und(U"i!:o a rc^adjustmeiit of rehitive position. It is certain that 

 the (dlicicMicy of predaceous enemies and of pai-asites is <i;ra(huilly 

 increasinir, while it is probable that the <2:radual a(laj)tati()n of the 

 weevil to its new environment is rendering it more resistant, esjx*- 

 cially to the effects of the adverse climatic factors. Additional 

 observations of the effects of these opposin"- tendencies should hriuLC 

 to liirht facts which will be of "eneral si<rnificance in connection with 

 the stud}' of many other pests besides the boll weevil. 



The area infested by the boll weevil in. the United States now 

 reaches a total of between 175,000 and 200,000 scjuare miles. Of 

 course but a snuill percentage of this enormous acreage is actually 

 devoted to cotton culture, but the range in geological conditions is 

 naturally great. Thus in Texas cotton is cultivated extensively on 

 five or six verv distinct oeolo^ical areas each furnishing more or less 

 distinctive conditions of environment affecting faunal, floral, and 

 shelter conditions which may at any time prove to have an impor- 

 tant significance in the wefevil status. 



INVESTIGATIONS SHOWING CONTROL BY HEAT, ANTS, AND 



PARASITES. 



Observations of the effect of various natural factors in controlling 

 the weevil have been accumulating since the beginning of the boll 

 weevil investigation. The earlier records, however, were not made 

 to include the simultaneous effect of several factors, and the records 

 presented in this connection are therefore confined to the observa- 

 tions made during 1906. 



Heat and drying are considered together, as their ellects upcm the 

 immature weevil stages are coincident and inseparable. The effi- 

 ciency of this factor naturally follows seas(mal variations, but it is 

 largely affected by the distance betw^een rows, the size of the plants 

 and density of their foliage, the season of occurrence in relation to 

 the state of the cotton crop, and by cultural conditions. 



Whenever ants are referred to in succeeding })ages it should he 

 understood that no reference is intended to the Guatemalan ''kelep" 

 {Ectatomma tuherculatum Oliv.), which has failed to maintain itself in 

 Texas. 



