LIME-SULPHUR A STOMACH POISON FOR INSECTS. 



83 



Arsenate of lead at strengths varying from ^-50 to 5-50 was used 

 in comparison with the lime-sulphur solution. Arsenate of lead and 

 lime-sulphur were also used together at various strengths (Tables 

 I and IV). In the case of the arsenate of lead and the lime- 

 sulphur most of the feeding was done during the first three or four 

 days. However, in no instance was there much feeding during the 

 first 24 hours, as the larvae were more or less unsettled until they 

 found a suitable place for their web. This was true on the unsprayed 

 as well as the sprayed leaves. 



It will be found in the following pages that the rate of killing is 



fairly uniform in all experiments. Since, however, the tests were 



conducted throughout the season under different climatic conditions, 



slight variations exist. 



RESULTS. 



Experiment I. 



The results given in Table I are taken from an experiment to obtain 

 data on the killing effect on the fall web worm of various chemicals 

 combined with lime-sulphur. Lot 1 was the unsprayed check; lot 2 

 was sprayed with lime-sulphur alone at the strength of H-50, and 

 lot 3 with lime-sulphur, H-50, in combination with arsenate of lead, 

 2-50. In the course of a few days it was observed that several larvae 

 on the lot sprayed with lime-sulphur were dying. The 20 larvae of this 

 lot were dead at the end of 13 days, as against 7 days required to kill 

 all the larvae with the combination of arsenate of lead and lime-sul- 

 phur. On the unsprayed lot, at the end of 72 days, 4 larvae were 

 recorded dead, 12 had pupated, and 4 were missing. 



Table I. — Tests of the killing effect on the fall webworm of lime-sulphur alone and com- 

 bined with arsenate of lead. 



[Experiment started July 20 



1912, Benton Harbor, Mich., 20 larvae in each lot.] 







Larvae dying in each lot. 



Date of examina- 

 tion. 



Larvae dying in each lot. 



Date of examina- 

 tion. 



• 



Lot 1— 

 Check 

 (un- 

 sprayed). 



Lot 2— 

 Lime- 

 sulphur, 

 l|-50. 



Lot 3— 

 Lime- 

 sulphur, 



1J-50, 



and 

 arsenate 

 oflead, 



2-50. 



Lotl— 

 Check 

 (un- 

 sprayed). 



Lot 2— 

 Lime- 

 sulphur, 

 H-50. 



Lot 3— 

 Lime- 

 sulphur. 

 l|-50, 

 and ■ 

 arsenate 

 oflead, 

 2-50. 



July 22 1 



23 .... 







Aug. 12 













14 







24 ' 





1 

 7 



10 

 2 



16 







25 





18 









26 . 



4 

 3 



3 



4 



21 









27 ! 



23 









28... 



Sept. 2 



1 

 2 







29 



19 







30. . 





30 







31 



4 





Total number 



dead 



Number of days re- 









Aug. 1... 





4 



20 



13 



0.73 





2 



2 





20 



3 







4 







7 



6 







Square inches of 

 foliage consumed . 



243. 20 





9 . 







0.12 











