L-Lactic acid was the major component in material isolated from humans that was active as an attractant for female yellow fever mosquitoes, Aedes aegypti (L.). The L(+)-isomer was several times as attractive as the D-isomer. Good correlation was found between the attractiveness of an individual to mosquitoes and the quantity of lactic acid present in an acetone washing of his hand.
The codistillation rate of DDT with water from a placid surface in µg. of DDT per gram of water parallels concentration from 1 to at least 100 p.p.b. at 25°, 30°, and 35°C. At the highest concentrations tested in this study, the codistillation rate was as much as six times greater than that which would be anticipated on the basis of the Rassow-Schultzky equation. This finding is in line with DDT's great affinity for the air-water interface, which facilitates the high codistillation rate. The significance of these results as related to the practical use of DDT is discussed.
Investigations of foreign and domestic plants are continually in progress in the Bureau of Entomology and Plant Quarantine for the discovery and development of new insecticides to replace those the supply of which has been curtailed by the war.In the course of these investigations attention was directed to the roots of the Mexican plant Erigeron affinis DC.1 (family Compositae), commonly called "peritre del pais" and "chilcuan." It grows in the vicinity of Mexico City, where the roots are employed in the preparation of native insecticides.That the petroleum ether extractive (3.3%, dry roots) prepared in this laboratory from the ground roots contained the toxic constituents was indicated by tests against codling moth larvae, adult mosquitoes, and several leaf-eating insects, and it proved to have the same order of paralyzing action and toxicity to houseflies as the pyrethrins.2The toxic fraction (1.9%, dry roots) was isolated from the petroleum ether extractive by the method that Barthel, Haller, and LaForge (1) employed for the preparation of pyrethrin concentrates for use in aerosols. Briefly, the nitromethane-soluble portion extracted from the petroleum ether extractive was passed through a column of activated carbon. When the solvent was removed from the purified nitromethane solution at reduced pressure, an oily residue possessing insecticidal activity was obtained, which was distilled at reduced pressure, and yielded 1.08% (dry-root basis) of light yellow distillate (b.p. 160-165°, p = 0.3-0.5 mm.), which crystallized when cooled but melted on standing at room temperature.The substance produced a burning, paralytic effect on the tongue similar t<> that caused by pyrethrin concentrates. It was soluble in organic solvents and contained nitrogen, but it was insoluble in aqueous alkali and acid. It rapidly decolorized a dilute chloroform solution of bromine and, on acid hydrolysis, yielded an acid and a base. Although the free acid was not identified, the base was found to be isobutylamine by determination of the melting point and the chlorine content of the base-hydrochloride and the melting point of the basechloroplatinate, and by comparison with authentic materials. The substance 1 The first specimen of roots was submitted under this name by Agencias Selectas, S. A., Mexico City. Subsequent samples were obtained through the courtesy of the Division of Fruitfly Investigations, Bureau of Entomology and Plant Quarantine, Mexico City. Attempts are being made to obtain a botanical specimen for confirmation of this identification. 2 The tests against the codling moth were made by E. H. Siegler; against mosquitoes by J. H. Fales and A. E. Routson; against several leaf-eating insects by Clemence Levin, and against the housefly by W. A. Gersdorff, all of this Bureau. Detailed results of their testswill be published elsewhere by them.
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