Monday, March 18, 2013

Butterfly of the Week: Black Swallowtail

Black Swallowtail

Papilio polyxenes (Fabricius 1775)

Status: Breeding resident.

Flight: Multiple brooded, with flights from April through early June, mid June through mid July, late July through August, and September through early October.

Distinguishing features: This easily recognized swallowtail is black, with two rows of submarginal yellow spots. The hind wing has a blue band between the yellow rows of spots, which are more extensive in females. The hind wing has a red spot at the anal angle and always has a black center. Wingspan: 6.7 - 11 cm.

Distribution and habitat: Map 294. Found commonly throughout the state in a variety of open habitats.

Natural history: Larvae of this species are particularly fond of cultivated and naturalized members of the carrot family, including parsley, dill, and carrots (including Queen Anne's lace), often decimating garden plantings of these vegetables. Because of the abundance of its host plants, it is often the most commonly observed swallowtail. Larval appearance changes across each of its four instar stages: the first two are bird-dropping mimics, the third is mostly black, and the fourth is green.

Questions: How often does this species use native members of the carrot family as a larval host? What are the selective advantages of having each larval stage appear different? What factors account for the marked size differences between populations often observed?

The Butterflies of Iowa, by Dennis W. Schlicht, John C. Downey, and Jeffrey C. Nekola

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