TOXICITY TO INSECTS AND MAMMALS OF FOODS CONTAINING SELENIUM

FOR MANY years it has been known that grains and forage plants grown on certain soils of the Great Plains produce fatal poisoning of livestock. Only recently, however, has the poison been identified as selenium, which is absorbed from the soil by the plants (for literature review, see Trelease and Martin, 1936). The problem assumes special importance through possible injury to human -beings from the consumption of seleniferous grains, vegetables, and animal products. In view of the high toxicity of seleniferous foodstuffs to mammals, birds, and some insects, we were surprised to find bruchids (beetles) and seed-chalcids (wasp-like insects) developing in seeds of Astragalus bisulcatus which were suspected of containing a high concentration of selenium. The present paper reports these observations and includes a comparison of the toxicity of similar seeds to white rats. THE INSECTS.-The seed pods of Astragalus bisulcatus (A. Gray) were collected by us in August, 1936, about five miles west of Laramie, Wyoming. Late in the following April the seeds were found to be heavily infested with bruchids (fig. 1, 2) and small hymenopterous insects. Both larvae and adults were present in large numbers. Mr. H. S. Barber, of the U. S. Bureau of Entomology, identified the bruchids (beetles)