MISCELLANEOUS INSECTICIDE INVESTIGATIONS. 



15 



used at the weaker strengths, apparently had no effect on the larvae. 

 The arsenate of lead killed all the larvae in 4 days. 



For the Datana ministra, the commercial lead chromate was used 

 at the rate of 8 pounds to 50 gallons of water, and at this strength 

 the killing effect of the material compared favorably with that of 

 arsenate of lead, 2 pounds to 50 gallons. The lead chromate, home- 

 made, was used at three strengths — f, 1^, and 3 pounds to 50 

 gallons of water. The weakest strength killed all the larvae in 6 

 days, the next stronger in 5 days. Only one larva had died in the 

 unsprayed lot at the time the experiment was closed, August 14. 



Experiment VIII. 



COMPARISON OF THE KILLING EFFECT OF ARSENATE OF LEAD, ARSENATE OF CALCIUM, 

 ARSENATE OF ZINC, ARSENITE OF ZINC, AND LEAD CHROMATE ON LARVAE OF THE 

 FALL WEBWORM. 



Different forms of arsenate of lead, arsenate of calcium, and lead 

 chromate were tested against the larvae of the fall webworm (Hy- 

 phantria cunea). Arsenate of zinc and arsenite of zinc were also 

 included in this test, as shown in Table VIII. 



Table VIII.- — Tests of the killing effect of various materials on the fall webworm. 

 [Experiment started July 23, 1913, Benton Harbor, Mich.; 20 larva? in each lot.] 





Name and dilution. 



Dates of examination and number of larvae dying 

 in each lot. 



■6 



03 

 <D 

 T3 

 Ul 



a 



R 

 o 



EH 



73 O 

 fc.T3 



.2 8 



a 3, 



3 a 1 



l-d 



en ° 



d 

 o 



July. 



August. 



24 



25 



26 



27 



28 



29 



30 



31 



1 



2 



3 



4 



a 103 



1 



Arsenate of lead paste, com- 





 





 





 





 





 





 





 





 





 





 

 

 





 1 





 





 



1 

 1 





 





 





 



1 

 1 





 





 

 

 





 1 





 2 



1 

 2 





 1 





 1 



2 

 1 





 



2 

 





 





 

 

 





 1 





 2 



5 

 1 



1 

 2 



7 

 3 



2 

 2 



1 

 1 



7 

 2 





 





 

 

 



4 

 10 



4 

 10 



7 

 6 



10 

 5 



11 

 15 



12 

 12 



18 

 16 



3 



8 



1 

 



1 

 

 

 



9 

 6 



9 



4 



7 

 9 



1 

 3 



2 

 1 



2 

 3 



1 

 3 



2 

 5 



9 

 5 



6 

 4 

 

 



7 

 1 



7 

 2 













20 

 20 



20 

 20 



20 

 20 



20 

 20 



20 



20 



20 

 20 



20 

 20 



20 

 20 



20 

 20 



20 



20 



3 



1 



7 

 7 



7 

 7 



6 



7 



8 

 8 



6 

 6 



7 

 7 



6 

 6 



8 

 8 



8 

 11 



10 

 12 



0.42 



? 



do 













.24 



3 



Arsenate of lead powder, 



commercial ( 1 ) , 1-50 



do : 













.41 



4 













.22 



5 



Arsenate of lead powder, 



commercial (2) , 1-50 



do 













.13 



6 



2 



5 

 5 













.24 



7 



Arsenate of calcium paste, 



2 

 3 











.75 



8 



do 











.88 



9 



Arsenate of calcium, home- 











.15 



10 

















.17 



11 



Arsenate of calcium, home- 



2 

 2 













.19 



1? 















.12 



13 



Arsenate of zinc, homemade, 

 t%-50 













.29 



14 

















.20 



15 



Arsenite of zinc powder, 



4 

 1 



8 

 5 



8 

 6 

 

 



1 

 3 



2 



7 



1 

 1 

 1 

 











.50 



16 



do 











.79 



17 



Lead chromate powder, 











.84 



IS 



do 



1 



2 

 3 

 

 



1 



2 

 4 

 

 



1 





2.01 



19 



Lead chromate, homemade, 

 U-50 



1.70 



?0 



do 



1 

 2 

 1 



1 

 

 



2.09 



?1 





20.17 



?2 



do 



20.56 









