Additions to Our Knowledge of the Toxicity of Stomach Poisons to Insects

Abstract

The so-called sandwich method was used to study the effect of calcium hydroxide, calcium caseinate, precipitated sulfur, dry Bordeaux mixture, and hydrated ferric oxide on the toxicity of acid lead arsenate for the fourth instar silkworm. No remarkable effect was produced by any of these substances. It is fairly certain, however, that calcium hydroxide and calcium caseinate increase the toxicity of acid lead arsenate when mixed with it in approximately equal proportions by weight: The indications are that precipitated sulfur may increase the toxicity of acid lead arsenate, and that dry Bordeaux mixture and hydrated ferric oxide may decrease it. Experiments were made by the sandwich method on the relative susceptibility to acid lead arsenate of the following caterpillars in the last instar: Eastern tent caterpillar (Malacosoma Americana Fab.), fall webworm (Hyphantria cunea Drury), walnut caterpillar (Datana integerrima G. & R.). and the catalpa sphinx (Ceratomia catalpae Boisd.) With the median lethal dose of acid lead arsenate for the fourth-instar silkworm as the standard of comparison, it was found that the first two insects were less susceptible and the last two more susceptible to acid lead arsenate than the fourth instar silkworm. It was also shown that, although the median lethal doses of acid lead arsenate and cuprous cyanide are different for the catalpa sphinx and silkworm, their relative toxicity is about the same for each of these insects. Certain improvements in the sandwich method are described.