Category: Eastern Tiger Swallowtail

Dark Morph of Eastern Tiger Swallowtail

The world of Nature always boggles my mind no matter what I am studying. There is always something that totally astounds me. One example is the dark morph of the female Eastern Tiger Swallowtail (Papilio glaucus). That’s one in the photo above. Yes, a Tiger Swallowtail. Not yellow, but black. Your location will influence how frequently you’ll see this dark form. The further south the more frequent. In the blog, BackyardWildlifeConnection, Terry W. Johnson says, “In middle Georgia, my neck of the woods, more than 90 percent of all female eastern tiger swallowtails are black.” Another site suggests that 10 percent of female population is the dark morph.

Higher numbers occur in the south because of the prevalence of the host plant of Pipevine Swallowtails (Battus philenor), Aristolochia which imparts a toxin (or an extremely bitter taste) to both the caterpillar and the butterfly. The female dark morph Tiger Swallowtail is mimicking the Pipevine Swallowtail. This mimicry gives these dark females protection, since those Pipevine Swallowtails are often avoided by predators because of their extremely bitter taste.

The dark female Tiger Swallowtail sometimes shows a trace of the tiger stripes, but to see the stripes the lighting must be just right. Very subtle. Males prefer yellow females, but the black form of the female is less attractive to predators so they have a higher survival rate. So yellow Tiger Swallowtails are either male or female. Dark Tiger Swallowtails are always female. Yellow females produce yellow offspring. Dark females produce dark offspring. This is one of those things in the world of Nature that is way beyond “just” impressive.

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Eastern Tiger Swallowtail

My first sighting this season was yesterday. The state insect of Virginia, the Eastern Tiger Swallowtail Butterfly (Papilio glaucus). Native to eastern North America. The butterfly I saw yesterday had just emerged from its chrysalis. Brand new.

This is what a chrysalis looks like. Though NOT an Eastern Tiger Swallowtail chrysalis, it looks to a large extent like one. One major difference would be more rich brown and less bright yellow. The shape is basically the same. This is a Pipevine Swallowtail (Battus philenor) chrysalis.

In the autumn an Eastern Tiger Swallowtail caterpillar will form itself into a chrysalis. NOT a cocoon but a chrysalis. Cocoons are used by moths. Chrysalises are used by butterflies. In ten to twenty days or over the winter the caterpillar makes incredible changes. As if by magic it will become a butterfly — to live just six to fourteen days.

Mainly males, after emerging, often will gather at puddles to take in sodium and minerals which tend to be lacking in the adult’s diet and are necessities for reproduction and flight. This is called “puddling.”

Speaking of reproduction, Eastern Tiger Swallowtails generally have two broods each year. Females lay their eggs on such trees as Tulip Poplar (Liriodendron tulipifera) and Wild Black Cherry (Prunus serotina). Those eggs will hatch in four to ten days as caterpillars. The earliest stage of the caterpillar looks just like bird droppings. The mature caterpillar is green, with eye spots, and a pale “neck ring.” Further to the front is a little purply-pink head.

Although most females look nearly like males, mostly yellow and black, there is a black form of the female Eastern Tiger Swallowtail. This is a method of protection. The black form is a mimic of the Pipevine Swallowtail (Battus philenor) which has a disagreeable taste. Predators have learned to avoid both the Pipevine Swallowtail and the Eastern Tiger Swallowtail’s black form. The portion of females with this coloring is more common in areas where there are more Pipevine Swallowtails.

The caterpillar becomes a chrysalis which becomes a dazzling butterfly. And so it goes. On and on.