366 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 9 



in relation to plant as well as animal life. While no positive state- 

 ments are possible owing to lack of sufficient data, 65 milligrams of 

 arsenous oxide (white arsenic) to 1,000 grams of live weight may 

 approximate the toxic dose^ for the horse, ox, sheep and fowl, and 9 

 milligrams for the dog and pig. On the former basis of susceptibility, 

 65 milligrams of arsenous oxide (equivalent chemically to 76 milligrams 

 of AS2O5) would kill 1,000 grams (net weight) of bees or 12,658 individual 

 workers^ weighing 79 milligrams each, or on the latter l)asis of sus- 

 ceptibiUty, 9 milligrams of arsenous oxide would accomplish the same 

 results. The toxic dose for bees is unquestionably small, whatever the 

 figure, as a considerable portion of the arsenic detected in the samples 

 was evidently in the bee load and not assimilated as shown by the 

 following treatment. A lot of bees containing arsenic, after being 

 shaken with 1 per cent nitric acid for 1 minute and rinsed twice with 

 water, gave only a "possible trace" of arsenic. Another portion 

 treated similarly with 3 per cent nitric acid would no longer react. 

 The use of 3 per cent acid proved inadvisable, however, as it Avas 

 found too active for even so short a period. The above test would 

 indicate that bees are susceptible to even less arsenic than is detected 

 in the original samples. 



The work w^ill be continued during the coming season with a view 

 ■of determining the amount of arsenic present. 



INJURY TO PEANUTS BY THE TWELVE-SPOTTED 

 CUCUMBER BEETLE^ 



{Diahrotica 12-punctata 01.) 



By David E. Fink, Entomological Assistant, Truck Crop and Stored Product Insect 



Ini'estigations 



Introduction 



The adult of the twelve-spotted cucumber beetle (Diabrotia 12- 

 punctata 01.) is well-known as nearly omnivorous in its feeding habits, 

 and in Tidewater Virginia, occurs on practically all truck crops. 

 Because of this omnivorous habit, their injury to any one particular 

 truck crop is sometimes nearly negligible, except at intervals when 

 few crops are in the fields. The larvie of this species are also well 



1 Calculated from data cited liy Nuiin, Veterinary Toxicology. 



^ Workers containing little or no feces average about 79 milligrams in weight; on 

 leaving the hive in the morning during the active season the feces may constitute an 

 additional 25 milligrams; a load of honey varies from 22 milligrams to several times 

 that weight. From various references furnished by Dr. B. N. Gates of this Station. 



* Published by permission of the Secretary of Agriculture. 



