Defense Mechanisms of Arthropods. XXXIV. Formic Acid and Acyclic Ketones in the Spray of a Caterpillar1

Many caterpillars of the family Notodontidae discharge an odorous spray when disturbed. The secretion stems from a large gland that opens ventrally in the neck region, and has been shown in Dicranura vinula (L.) (Poulton 1888, Schildknecht and Schmidt 1963) and Schizura leptinoides (Grote) (Monro et al. 1962) to contain formic acid. Recently, while handling larvae of the common notodontid Heterocampa manteo Doubleday2 in the field, we noted that its spray has an anomalous odor, pungent and reminiscent of formic acid, but clearly indicative of the presence of additional components. We here report on the chemistry of the mixture.