154 



ARTIFICIAL COXTHOL. 

 EFFECT OF BTJBYING SQUARES AND WEEVILS. 



EFFECT UPON PUPATION AND ESCAPE OF ADULTS IN DRY SOIL. 



riie experiments made upon this point were designed to ascertain 

 the value, if any, in the plowing under of squares as a means of 

 destro3'ing the larvae and pupai infesting them. But few experiments 

 seemed necessary to demonstrate the futility of this operation alone as 

 a means of controlling the weevil. 



Squares which were known to be infested with about half -grown 

 larvae were placed in glass jars and covered with several inches of 

 quite dry and fairl}" well-pulverized earth. When examination was 

 made it was found that pupation had taken place normally while the 

 squares were buried under from 2 to 5 inches of dirt. In no case was 

 pupation prevented, though a few weevils did not leave the squares 

 after having become adult. Altogether about 100 squares were thus 

 buried, and from them over 75 weevils emerged. 



In a portion, of the preceding tests careful examination was made 

 to ascertain how far toward the surface the newly emerged weevils 

 had succeeded in getting before they perished. It should be noted 

 that these weevils had never fed, and thej would have, therefore, less 

 strength and endurance than such fully hardened adults as might be 

 buried in the ordinary processes of field cultivation. Furthermore, 

 the soil used was of finer texture and more compactlj^ settled than it 

 would be in the field. Twenty-seven weevils were found in this exam- 

 ination, their location varying from the bottom of the jar to their 

 having escaped through 4 inches of soil. A weighted average shows, 

 however, that each weevil had made its way upward through 2 inches 

 of dirt. We may infer, therefore, that had these squares been buried 

 under less than 2 inches of fairly well-pulverized earth, as would be 

 the case from field cultivation, but a snail percentage of them would 

 have failed to make their way out. As it was, fully three-fourths of 

 those leaving the squares made their waj^ out through more than 2 

 inches of dirt. 



EFFECT OF BURYING IN WET SOIL. 



In a series of experiments in which 342 squares were buried under 

 wet soil at various depths subsequent examination showed that 37.7 

 per cent contained no weevils at the time of burying. Among 139 

 squares removed at varying intervals for examination, 13.7 per cent of 

 the inclosed stages were found to be dead. Among 74 squares left until 

 after maturity should have been reached, 16.2 per cent of the inclosed 

 stages were dead. Of the weevils becoming adult, 30.6 per cent 

 emerged from the squares, but only 23 per cent reached the surface or 



