CONTROL BY HEAT, ANTS, AND PARASITES. 25 



a general thing the emergence hole made by the weevil (PL TIT, fig. 1 ) 

 is more regular in outline and somewhat larger in area than are the 

 entrance holes made by the ants. ' Upon opening the square carefully 

 it will be found that if a weevil has reached full development therein 

 and emerged, there will be found present three definite signs which are 

 not present in cases where ants have destroyed the weevil stage. One 

 of these signs is the delicate white skin which is shed by a pupa 

 when the weevil transforms from that stage to its adult condition. 

 (PI. Ill, fig. 5a.) This is usually so shriveled and twisted as to have 

 no resemblance whatever to the outlines of a living pupa and is fre- 

 quently more or less hidden in the debris which constitutes the second 

 sign. This is a rather abundant mass of fine particles which have 

 been torn from the square by the weevil in cutting its emergence hole. 

 These are not eaten by the weevil but are left within its cell (PL III, 

 figs. 3 and 5b) . The third sign of adult activity consists of a number 

 of particles of white excrement which are almost invariably deposited 

 by the adult weevil before its emergence from the square (PL III, 

 figs. 3 and 5c). These three signs are absent in cases where ants 

 have entered and destroyed the weevil stages (PL III, fig. 4). 



The value of a study based upon statistical data becomes easily 

 apparent to one engaged in a thorough study of such a subject as this. 

 Without it there is a strong probability that the general impressions 

 formed may not give proper credit to the influence of the various 

 factors. Conclusions which are based upon the total effects of the 

 various factors in a large series of observations must necessarily be 

 more reliable. This must be especially true of the general average of 

 results from a considerable number of localities and under a consider- 

 able variety of geological and climatic conditions. 



The first division in the data as obtained has been secured b} r sepa- 

 rating the cotton fruit into several classes, each of wmich may contain 

 weevil stages which have been exposed to similar conditions. But 

 four of these divisions have been retained in the arrangement of the 

 data shown in Table III. These are, (a) hanging, dried bolls; (b) 

 hanging, dried squares; (c) fallen bolls; (d) fallen squares. As a rule 

 infested squares and small bolls are shed by the plant in from seven to 

 twelve days after the weevil attack. Many small bolls, especially, 

 are shed . normally, even though they may have suffered no injury 

 from insect attack. This happens most commonly within a few days 

 after the withering of the flower and before the young boll has made 

 any growth. It may result from a failure in fertilization of the flower 

 or the inability of the plant to sustain an excessive load of fruit. 

 With both squares and small bolls, the shedding is accomplished 

 naturally, just as is the shedding of leaves in the autumn, by the for- 

 mation of an absciss layer of corky cells which cuts oil' t be fibrovascu- 

 lar bundles through which the sap is supplied, thus destroying the 

 vital connection between the bud or boll and the plant branch. The 



