October, '15] 



TARTAR-WILSOX: ARSENATES OF LEAD 



485 



A few caterpillars begin feeding immediately upon being trans- 

 ferred. These are usually quite hungr}^ and eat considerably before 

 stopping. The others feed later at a time more or less regular to their 

 habits and eat according to their hunger, some eating rapidly and 

 devouring considerable foliage before the poison can act. Others eat 

 only a small amount or eat slower and although the}^ become sick they 

 manage to survive for a longer period in proportion to the amount 

 eaten. The behavior of the poisoned caterpillars is practically the 

 same in all cases but varies considerably with the amount eaten. 

 Usually those that are slightly sick wander around to a more or less 

 extent but do not feed and if possible they will leave the twigs. Those 

 with larger doses cluster together and gradually become sluggish, being 

 at first sufficiently active to move the head and forepart of the body 

 -from side to side when disturbed. Later they barely move and finally 

 may drop off or remain suspended from the tent by the prologs. 



Chemical Analyses 



The chemical analysis of the poisoned caterpillars from each of the 

 tests was made by first drying at 100 degrees centigrade to get the 

 actual weight of the dry tissue of the insects. Then the arsenic was 

 determined in the following manner: A quantity of the dried tissue, 

 not exceeding 4 grams, was introduced in a Kjeldahl flask, 500 cc. 

 capacity, and about 15 cc. of arsenic free concentrated sulfuric acid 

 added. The flask was then placed over a medium flame and heated 

 until fumes of sulfur dioxide were given off. Fuming nitric acid 

 (arsenic free) was next added in small quantities (2 cc.) at short inter- 

 vals until all the organic matter was oxidized and the solution was 

 perfectly clear. The solution was then cligested over a hot flame for 

 two hours. Following the digestion the excess of sulfuric acid was 

 carefully driven off and the arsenic determined by titration with 

 fiftieth-normal iodine solution after reduction with potassium iodide, 

 accorcUng to the modified Gooch and Browning method (Bui. 107 

 Revised, Bureau of Chemistry, U. S. Dept. of Agr., p. 239). The 

 results were calculated in terms of milligrams of arsenic oxide, AS2O5. 



The data obtained from the analytical work are given in the follow- 

 ing tables. 



For convenience in making comparisons, the milligrams of arsenic 

 oxide in 1 gram of dried tissue have been estimated in each instance. 



