Other Common Names
Eastern Black Swallowtail
Dill Worm, Parsley Worm, Celery Worm
Carrot Worm, Fennel Worm
Explanation of Names
Papilio polyxenes Fabricius, 1775
The common names for the caterpillars vary because they can be found on many important cultivated plants in the Carrot Family. Pick the host plant, add the word "worm", and you have another common name that has probably been used and published somewhere.
Adult: a common member of the "blue-and-black" swallowtail complex. Female, with its large blue patches on hindwings, is a mimic of the Pipevine Swallowtail. Some female Black Swallowtails have little yellow on wings above. Males have more extensive broken yellow band. Note orange and black spot on inner margin of hindwings (Palamedes Swallowtail is otherwise very similar, above, but has no black center in the orange spot).
Female (below left) Male ( below right)
Underneath, the median orange spot-band varies in thickness.
Larva changes color quite dramatically with each molt. Last instar is green with black bands dotted with orange or yellow spots on each segment; pupa has two forms - brown and green.
e NA to s. CA / Mex. to S. Amer. - Map
Open areas, meadows, fields, gardens
April-October in north, 2 broods. Longer flight, with three broods in southern US.
Larvae feed primarily on plants of the carrot family (Apiaceae = Umbelliferae), and some in the Rue Family (Rutaceae). Commonly found on Dill, Parsley, Fennel, Carrot, and Rue in gardens, and Queen-Anne's-Lace, Poison Hemlock, and Lovage in the wild. They will occasionally be found on Citrus trees.
Adults take nectar and frequently visit moist ground.
overwinters as a pupa
This composite image shows several larval instars, pupa/chrysalis and adult butterfly
The Black Swallowtail appears to interbreed fairly regularly with its close relative the Old World Swallowtail
) in Manitoba and Saskatchewan. The dark offspring, formerly thought to be a distinct species (Papilio kahli
), are widespread in Manitoba, but scarce; they feed as larvae mainly on Heart-leaved Alexander (Zizia aptera
[from Butterflies of Canada; CBIF]
Larvae and pupae are parasitized by members of the following families: Phoridae, Tachinidae, Ichneumonidae, and Braconidae (Ecological monographs
In eastern US, compare Pipevine Swallowtail
, Spicebush Swallowtail
, Palamedes Swallowtail
and Red-spotted Purple
(which has no tails). A comparison of the underside of the hindwings is helpful for ID:
Pipevine - single row of orange spots which do not touch
Spicebush - missing one orange spot in the median row
Palamedes Swallowtail - stripes on body and front part of wing
Red-spotted Purple - no tails, single row of orange spots
Eastern Tiger Swallowtail, dark female form - faint darker tiger striping visible, no median spot-band. Orange spots are at edge of wing, with blue band above them.
Butterfly Gardening and Conservation.com
has images of different larval instars and colors.