Biomedical Ephemera, or: A Frog for Your Boils

Black Swallowtail (Papilio polyxenes) on hostplant (Anethum sp. or Daucus sp.)

Though the exact colors and markings vary between subspecies (and even within subspecies), you can see the sexual dimorphism (phenotypic differences) between the male and the female black swallowtail here. [ETA: The female is the lower right, the male is top left]

In many butterfly species, the female is polymorphic, and can have multiple phenotypes, some even being identical to the male phenotype. What is shown here is considered the "type" (standard) for the black swallowtail species, but nearly half of the females are phenotypically different from this form. However, even when the female looks exactly the same as the male to the human eye, they maintain a distinct pattern of UV markings, that are easily visible to other butterflies.

The Natural History of the Rarer Lepidopterous Insects of Georgia, vol. 1. Sir James Edward Smith, Illustrated by John Abbot, 1797.

1, 4 - Pipevine Swallowtail (Battus philenor) 2, 3, 5 - Black Swallowtail (Papilio polyxenes)

As can be seen here, the black swallowtail is very similar to the toxic and bad-tasting pipevine swallowtail. It is also nearly identical to the Ozark swallowtail, and was once considered synonymous with it. However, molecular genetics have proven that the Ozark swallowtail is actually descended from a completely different line of Old World butterflies.

The similarities between the black swallowtail and the pipevine swallowtail are known as Mullerian mimicry. This form of mimicry is when two species share the same warning signals to predators and both share genuine anti-predation attributes. Both butterflies are unpalatable to predators, and if a predator eats one member of either species, it learns to avoid both of them (as they look very similar). This can also be considered a form of mutualism, as both mimic and original model benefit from this "interaction".

Illustrations of Exotic Entomology. J. O. Westwood, from illustrations by the late Dru Drury, 1837.

Coral Snakes vs. the King Snake

King snakes (and milk snakes) look much like the highly venomous coral snake, and many species avoid them because of this. This is an excellent example of Batesian Mimicry.

Snake Venoms: An Investigation of Venomous Snakes, with Special Reference to the Phenomena of Their Venoms. By Hideyo Noguchi M. D., 1909.