Swallowtails
What are they?
Swallowtails are large and attractive butterflies with a bouyant and graceful flight style. A number of species feed on toxic plants during their larval (caterpillar) stage and retain these toxins into their adult stage, making them unpalatable to most predators. This fact is reflected in the appearance of the larvae and in a number of the adults which sport warning red spots.
Identification
The largely black species of swallowtail in our region can be tricky to tell apart but are soon learnt with experience. Key features to look for include the pattern of the underside of the hindwing and the pattern of pale markings on the upperside of the forewing.
Pipevine Swallowtail Battus philenor
Wingspan: 3.6 inches. Flight time: May to October. Larval foodplant: Pipevines (Aristolochia spp.) A scarce visitor to our region and probably not completely established here, relying on regular immigrations from the south to keep the population going. Pipevines are very rare in Cape May County and most known occurences of larvae of this species here come from ornamental pipevines in gardens and back yards. This is a highly toxic species to predators and consequently is mimiced by a number of other species, who benefit from their similarity by being left alone. This species can be identified by its rather plain upperwing and by the regular row of red spots on the underside of the hindwing.
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Spicebush Swallowtail Papilio troilus
Wingspan: 4.1 inches. Flight time: May to September. Larval foodplant: Sassafras and Northern Spicebush. Widespread and common throughout the county, especially in lightly wooded, marginal areas and field edges where Sassafras is common. Similar to Pipevine Swallowtail but note the missing red spot on the underside of the hindwing, which is replaced by a pale blue mark resembling a comet.
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Black Swallowtail Papilio polyxenes
Wingspan: 3.2 inches. Flight time: April to October. Larval foodplant: Members of the carrot family (Apiaceae), especially Wild Carrot and Fennel. Widespread and common throughout the county, favoring open fields and backyards where larval foodplants grow. A little smaller than the other black swallowtails and often with a stiffer flight style. Differs from our other swallowtails in that the sexes can be told apart by their wing patterns: Males have more yellow spots on the forewing and females have more blue on the hindwing. Both sexes can be told from other species by the extra pale spot near the leading edge of the forewing (both above and below) and by the pattern of red spots on the underside of the hindwing.
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Eastern Tiger Swallowtail Papilio glaucus
Wingspan: 4.8 inches. Flight time: May to September. Larval foodplant: Leaves of a wide range of trees. Widespread throughout the county but usually only seen in small numbers. Our largest swallowtail and readily identified by its predominantly yellow wings with black tiger-stripes. Occasionally found in a dark morph.
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| hindwing upperside |
hindwing underside |
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Giant Swallowtail Papilio cresphontes
Wingspan: 4.8 inches. Flight time: August to September. Larval foodplant: Citrus fruits and other members of the Rutaceae. An irregular vagrant from the south, not recorded in most years. Despite the name, this species is about the same size as the familiar Eastern Tiger Swallowtail, though it has a more attenuated forewing shape. Unique in our region in being predominantly black above and yellow below.
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