Toxicity of Selected Organic Compounds to Insects: Part I. Tests for General Toxicity on Larvae of Musca, Tribolium, and Ephestia, and Adults of Sitophilus

The general toxicity of 127 synthetic organic compounds was tested against larvae of Musca domestica, Tribolium confusum, and Ephestia kuehniella, and adults of Sitophilus granarius. The compounds were mixed in the insects' food in graded concentrations, and their toxicity was assessed by determination of the median lethal concentrations (LC 50 ) for each of the four species. The most highly toxic compounds were gammexane (the gamma isomer of hexachlorocyclohexane) and chlordane (obtained by distillation of technical chlordane). The toxicity of DDT was on the average one-half of that of the first two compounds, and it was superior to any of the 12 analogues tested. Four chlorinated aliphatic hydrocarbons, namely hexachloropropene, hexachlorobutadiene, and the symm-and asymm-heptachloropropanes, showed a high toxicity related to their powerful fumigant action. A high level of toxicity was shown by benzyl thiocyanate and its chlorinated derivatives. The nitro compounds dinitro-o-cresol, nitrostyrene, dinitrodimethylbutane and dinitrocyclohexylphenol were especially toxic to Sitophilus adults, but were ineffective against Musca larvae. Certain aromatic semicarbazones recommended by previous workers gave disappointing results. Of 22 derivatives of morpholine tested, only three showed any degree of toxicity to the four species of insects employed.