Thursday, March 5, 2009

New In The Park - Caterpillars

Black Swallowtail (Papilio polyxenes)

Well, its been a relatively mild winter here in Houston, with few really cold periods. The cold snaps we had, though fairly cold for the region, didn't last for more than a few days at a time. This and the the current warm February and March weather has lead to early wildflower bloom and butterflies laying eggs weeks early. We already have Monarchs on the Milkweed and Gulf Fritillaries on the Passion Vines.

Something I noticed a few days ago were a few Black Swallowtail caterpillars on the Dill and Fennel plants in the park's herb garden. This isn't that common an occurrence in our park, regardelss of the early appearance, so its quite a pleasant surprise.

A close up view of 2 polyxenes caterpillars on one plant. The mother only lays 1 or 2 eggs on each larval host plant.

The Black Swallowtail caterpillar can extend its osmeterium when threatened. Only the Swallowtail caterpillars (there are man varieties of Swallowtail) have these. The osmeterium releases unpleasant odors when extended, and may help to visually shock a predator.

2 Caterpillars on the flower stalk of a Dill plant (Anethum graveolens)

Black Swallowtail caterpillars are always found on plants in the Carrot Family (Apiaceae), like this Green Fennel (Foeniculum vulgare) in someone's garden.

The chrysalis of a Black Swallowtail, which are much harder to find than the caterpillars.

Adult Papilio polyxenes mating

The very tiny egg of the Black on the leaflet of an Italian Parsley (Petroselinum crispum)

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