100 



LABORATORY OBSERVATIONS UPON TIME WEEVILS WILL FLOAT OR 

 ENDURE SUBMERGENCE. 



Tliese tests were divided into two parts, each of wliich includes 

 both the immature and mature stages. In each i^art floating and 

 submergence were tested. 



Sixty squares, believed from external examination to be infested, 

 were floated in a driving rain for six hours. They were then removed 

 and left for several days, during which time 75 per cent of them pro- 

 duced normal adults. Ten squares which were floated in driving rain 

 for six hours were opened at once, and in every case found to be but 

 slightly wet upon the inside. These contained 6 larva? and 4 pupse, 

 and all were in perfect condition. 



As squares float normally, submergence tests were considered 

 extreme. Five squares were submerged for six hours, and after that 

 produced 3 normal adults; 1 pupa died, and 1 square was found to 

 have been uninf ested. Five more squares were submerged for thirty- 

 one hours. These produced 2 normal adults, and 1 pupa died in the 

 process of molting after removal from the square. Death was prob- 

 ably caused in the last case by drying; 1 square was found to contain 

 a dead pupa, and 1 was not infested. To test the possibility of its 

 living, should the square be penetrated by water, a naked pupa was 

 submerged for six hours, but in spite of this unusual treatment it 

 produced a normal adult. 



In the tests made upon the floating power of adults, weevils Ave re 

 isolated and placed in water in tumblers. They were droj)ped from a 

 considerable distance above the surface, so that they became entirely 

 submerged, and then floated to the surface naturally. The surface 

 tension of the water was found to be sufficient to float weevils which 

 were placed upon it carefully. The generally hairy condition of the 

 surface of the weevil's body prevents its being readily wetted, so that 

 it may struggle for some time in the water without becoming really 

 wet. When dropped in this way weevils float head downward, with 

 the tip of the abdomen above the surface. In the submergence tests 

 weevils were held down by a wire screen, and all bubbles were 

 removed from their bodies by a pipette, thus making the tests as 

 severe as possible. 



