486 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 8 



EXPERBTENT No. 1 



No. 



Spray 



No. of Cater- 

 pillars 



Weight of Dry- 

 Tissue (Grams) 



MiUigrams of 

 Arsenic Oxide 

 (AssOs) 



Milligrams of Arsenic 

 Oxide (AsiOs) to 1 

 gram of Dry Tissue. 



1 



2:50 L.H.A. 



445 



3.973 



2.96 



0.74 



2 



2:50 B.L.A. 



205 



1.423 



0.86 



0.60 



3 



2:100 L.HA. 



341 



1.262 



0.86 



0.68 



4 



2:100 B.L.A. 



202 



1.623 



0.48 



0.30 



5 



2:200 L.H.A. 



371 



1.751 



0.40 



0.23 



6 



2:200 B.LA. 



220 



1,056 



Tracei 





7 



2:400 L.HA. 



332 



1.674 



0.34 



0.20 



8 



2:400 B.LA. 



201 



.831 



Trace 





9 



2:800 L.H.A. 



418 



1.337 



0.08 



0.06 



10 



2:800 B.L .A. 



291 



2.035 



0.28 



0.14 



1 One drop fiftieth normal iodine for titration. 



ExPEHiME>~r No. 2 



No. 



Spray 



No. of Cater- 

 pillars 



Weight of Drj- 

 Tissue (Grams) 



Milligrams of 

 Arsenic Oxide 

 (AssOs) 



MiUigrams of Arsenic 

 Oxide (AS2O5) to 1 

 Gram of Diy- Tissue. 



1 



2:50 L.H.A. 



176 



3.383 



2.30 



0.62 



2 



2:50 B.L.A. 



261 



3.520 



1.72 



0.49 



3 



2:100 L.H.A. 



240 



4.046 



1.86 



0.46 



4 



2:100 B.LA. 



191 



3.150 



1.50 



0.47 



5 



2:200 L.H.A. 



185 



2.990 



0.72 



0.24 



6 



2:200 B.L.A. 



453 



4.835 



1.29 



0.26 



7 



2:400 L.H.A. 



302 



3.790 



0.86 



0.23 



8 



2:400 B.L.A. 



284 



3.222 



0.57 



0.18 



9 



2:800 L.H.A. 



284 



3.719 



0.43 



0.11 



10 



2:800 B.L.A. 



152 



2.303 



0.15 



0.06 



11 



2:1200 L.HA. 



280 



3.582 



0.28 



0.08 



12 



2:1200 B.L.A. 



223 



2.354 



0.15 



0.06 



These results show that in most cases the arsenic content of the 

 caterpillars poisoned with the lead hydrogen arsenate was somewhat 

 greater. This fact may be partly due to the higher arsenic content of 

 this compound. It is also possible that this substance, being more 

 chemically reactive, is more rapidly absorbed into the tissues while 

 the inert basic compound passes through the intestinal tract of the 

 insect without the absorption of so much of the arsenic. 



In conclusion, we acknowledge our indebtedness to Mr. H. H. 

 Robinson who assisted in making the chemical analyses here 

 reported and to yir. G. F. ]Moznette who assisted in the Entomological 

 work. 



Vice-President Cooley: Mr. George P. Gray will present the 

 next paper. 



