The Black Swallowtail looks almost identical to the pungent-tasting Pipevine Swallowtail. This mimicry is a good defense against predators. The caterpillar of the Black Swallowtail also has a defensive organ called an osmeterium. This "Y" shaped, fleshy organ is normally hidden, but will protrude if the caterpillar is threatened. It can then emit terpenes, an organic chemical that smells quite foul and discourages would-be predators from eating the caterpillar.
The body of the Black Swallowtail is black with rows of small white dots running down the length of it. The dorsal (back) view displays black forewings edged in two rows of white dots. Two larger spots are close to the edge. The smaller, black hindwings also have two rows of white dots, but an iridescent blue is sandwiched between them. Each hindwing sports a bright orange and black eyespot at the bottom near the body. The edges of the hindwings are scalloped with white inside the curves. A long extension forms a 'tail' on each wing. Most of the desert populations are more yellow in color, while other populations have less color.
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* MAP NOTES: The territorial heat map above showcases (in red) the states and territories of North America where the Black Swallowtail may be found (but is not limited to). This sort of data is useful when attempting to see concentrations of particular species across the continent as well as revealing possible migratory patterns over a species' given lifespan. Some insects are naturally confined by environment, weather, mating habits, food resources and the like while others see widespread expansion across most, or all, of North America. States/Territories shown above are a general indicator of areas inhabited by the Black Swallowtail. Insects generally go where they please, typically driven by diet, environmental changes, and / or mating habits.