﻿AESENICALS. 



41 



Table 19. — Relative toxicity of pure arsenic oxi/Is and of bases on 4 specks of insects 

 after deducting mortality of control with food, 1919 — Continued. 



Material and controls. 



Percentage of insects dead within— 



10 days. 



20 days. 



m 



22 



a 8 





Arsenious oxid , 



Arsenic oxid 



Calcium oxid 



Calcium arsenate. . . 



Lead oxid 



Acid lead arsenate. . 



Zinc oxid 



Zincarsenite 



Magnesium oxid 



Magnesium arsenate 



Copper oxid 



Paris green 



Copper barium arsenate 



Barium oxid 



Barium arsenate 



Control without food. 



Control with food 



Control with food, 

 omitting tent cater- 

 pillars 



70.0 



"76 



2.0 

 100.0 

 .0 



71.5 

 .0 



95.6 



94.2 



.0 



92.7 



.0 



93.7 



.0 



66.7 



1.3 



84.7 



.0 



93.7 



91.1 



6.4 



66.9 



93.6 



4.1 



78.9 

 87.6 



1.1 

 87.7 



4.8 



87.3 



.0 



86.9 



23.9 

 51.7 

 .0 

 51.8 

 45.7 

 45.5 

 13.3 

 45.6 



1.7 



55.5 



.0 



47.9 



54.1 



5.1 

 52.1 



67. 1 

 83.4 

 .3 

 83.0 

 24.3 

 81.6 

 3.8 

 74.8 



86.0 

 "76 



ioo.'o 



"<5."6 



"76' 

 "i'6' 



79.3 

 12.3 



42.5 



14.7 



100.0 

 .0 



All. 



All. 



.0 



All. 



4.1 



All. 



.0 



70.2 



2.2 

 74.8 



2.5 

 All. 

 All. 



7.7 

 66.3 

 All. 

 21.0 



All. 

 All. 

 0.0 

 All. 

 0.0 

 All. 

 0.0 

 All. 



All. 

 50.5 



35. 1 

 All. 



1.7 

 All. 

 All. 

 All. 

 24.1 

 All. 



8.6 

 All. 



0.0 

 All. 

 All. 



8.7 

 All. 



57.1 



94.6 

 100.0 

 26.9 

 100.0 

 65.3 

 100.0 

 35.0 

 97.8 

 29.6 

 97.9 

 27.0 

 100.0 

 100.0 

 47.2 

 93.7 

 100.0 

 32.2 



26.0 



46.1 9.0 



76.5 I 3.5 



0.2 143.4 



73.5 

 18.3 

 74.5 

 2.6 

 66.9 



8.5 



7.4 



148.6 

 2.8 



119.8 

 22.0 



105. 5 

 14.2 



106.9 

 3.9 

 10.8 

 70.3 

 28.0 



100.0 



1 First 8 and next to the last figures to be compared; next 8 and last figures to be compared. 

 s Based on webworms (H. cunea) and tent caterpillars. 



Comparing the mortality of the insects fed on the various bases 

 with that of the control insects (Table 19), it appears that calcium 

 oxid is beneficial to insects (sample 11, 26.9 per cent, and control, 

 32.2 per cent), that zinc oxid (sample 22, 35 per cent, and control, 

 32.2 per cent), magnesium oxid and copper oxid (samples 63 and 

 65, 29.6 per cent and 27 per cent, and control, 26 per cent) are 

 slightly injurious, that barium oxid (sample 72, 47.2 per cent, and 

 control, 26 per cent) is moderately injurious, and that lead oxid 

 (sample 12, 65.3 per cent, and control, 32.2 per cent) is the most 

 effective of all the bases used. 



Since the arsenious oxid (sample 9) used in the 1919 experiments 

 had a low toxicity, a commercial white arsenic (As 2 3 ) was used in 

 the experiments conducted in 1920. Sample 9 contained only 17.77 

 per cent of water-soluble arsenious oxid, while sample 27 contained 

 38 per cent. To obtain its average toxicity on four species of insects 

 in comparison with the toxicities of pure arsenic oxid (sample 10) 

 and acid lead arsenate (sample 39), the following insects were used: 

 Silkworms, 2 sets (each of 50); webworms (H. cunea), 1 set (varia- 

 tion 100-136, average 120); tent caterpillars, 3 sets (221-446, aver- 

 age 292); and honeybees, 2 sets (each of 50). The average per- 

 centages of toxicity are as follows: Sample 27 (arsenious oxid), 

 62.4; sample 10 (arsenic oxid), 74.3; and sample 39 (acid lead arse- 

 nate), 71.2. 



