December, '22] larson: metallic mercury as an insecticide 393 



vial 1.7 X 6.5 cm. containing about 1 cc. of mercury. The smaller 

 vial containing a perforated cork was placed upright and the larger 

 vials were set aside for observations. 



In one week it was noted that eggs in the one vial were hatching, 

 while those in the other were not. In another week it was observed 

 that the larvae from the eggs in the one vial had almost all entered 

 the cowpeas, while in the other vial not an egg had hatched. 



On August 15th, after removing the vial of mercury, it was found 

 that every egg that had been in the larger vial, along with the mercury, 

 had shriveled up and appeared to have nothing inside of the chorion. 

 These eggs were remarkable for the absence of all contents within. 

 They were absolutely hollow. There was nothing to indicate that de- 

 velopment had ever begun. 



August 16th the cowpeas in the other vial were dissected and four 

 live pupae, 74 live larvae and 8 dead larvae were found within. 86%, 

 of the eggs had actually produced larvae, and others showed embryonic 

 development, while in the other vial there appeared to be absolutely 

 no embryonic development. No mold appeared in either vial. 



On July 25th several pairs of weevils, B. quadrimaculatus, were 

 placed in a jar of red ripper cowpeas. These weevils oviposited freely, 

 covering the cowpeas with varying numbers of eggs up to 15 or more, 

 but averaging 8 or 9. Most of the weevils died before August 15th, 

 and the greater number of eggs were laid during the early part of the 

 period from July 25th to August 15th; in fact, man^^ of the eggs had 

 hatched and the larvae had entered before the latter date. 



On August 15th two hundred of the cowpeas were counted out and 

 placed in two vials 10 x 3.2 cm. Into the one vial was put a small 

 vial (1.7 X 6.5) containing about one-half thimbleful of mercury. The 

 cowpeas were arranged around the small vial which contained a per- 

 forated stopper. Tight stoppers were placed in both large vials, and 

 they were placed side by side on a shelf for observation. For con- 

 venience they were labeled "mercury vial" and "check vial." 



In a short time it appeared that weevils were at work in the "check 

 vial," because borings and frass began to exude from the cowpeas. 

 It soon became evident that the lack of proper ventilation in this vial 

 was being felt by the weevils. They made openings through the seed 

 coat, and three half-grown larvae left the cowpeas and died. By 

 October 29th, mold began to appear in the vial. This mold developed 

 so rapidly that it was feared that it would kill all the enclosed weevils; 

 therefore on November 4th these cowpeas were placed in four clean 

 dry vials similar to the original. These vials were laid down so that 



