I soon confirmed my initial suspicions as to the identity of the culprits that laid these once fat bunches of parsley to waste. On the branches were 19 brightly banded larvae of the black swallowtail, Papilio polyxenes, polishing off the last few leaves. As I touchedthe top of one the caterpillar reacted immediately by assuming defensive postures. Bent over backwards, they spit up green fluid and produced a pair of long tentacles (osmeterium), that resembled bright orange horns. Soon my nostrils were filled with a strong, disagreeable odor that is best described as “spicy vomit.” The osmeterium consists of two soft, finger-like tubes that are everted from inside the body through a slit in the prothorax just behind the head as a result of increased blood pressure. This defensive gland is found in the caterpillars of swallowtail butterflies and is coated with highly noxious chemical compounds (2-methylbutyric acid and isobutyric acid) that deter predators, especially ants.
Posted on: Sat, 08 Jun 2013 22:40:43 +0000
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