This humble vine is at the center of a evolutionary tangle of butterflies:
Woolly Pipevine, aka Dutchman's Pipe, Aristolochia tomentosa.
The vine makes poisonous defensive compounds which keep away most chewing insects. But pipevine swallowtails have evolved the ability to not only eat the pipevine, but to sequester its nasty chemicals, taking on a protective mantle. The poisons are stored by caterpillars when they feed on the vine and the chemicals are retained in the bodies of adult butterflies. The butterflies advertise their distastefulness with distinctive blue and black colors. Few birds or other predators are interested in attacking this species.
Pipevine swallowtail (photographed earlier this summer, as were all the butterflies that follow)
This bad-tasting butterfly carries a gaggle of other species in its wake. These others lack the defensive chemicals, but mimic the blue and black colors, gaining protection through false advertising. This kind of mimicry is called Batesian mimicry, after Henry Walter Bates, a Victorian naturalist who first described the phenomenon in the rainforests of South America.
Mimic 1: Spicebush swallowtail
Mimic 2: Red-spotted purple
Mimic 3: Female tiger swallowtail (males are yellow and black). The females can also be yellow and black; the proportion of mimetic forms increases in areas with more pipevine swallowtails.
Humans also use the chemicals in pipevine as a herbal medicine, but the severe toxicity of the aristolochic acids in the plant make this risky medicine, at best.
Despite a wet start with few butterflies visible, the day dried out and warmed up and finally yielded thirty three species, one shy of our record from 2008. The best butterfly of the day was a goatweed leafwing, a very rare species for Sewanee.
I was lucky to get this photo. Pearly-eyes usually fly away when approached too closely. Note the black bases to the clubs at the end of the antennae — this distinguishes the Northern from the Southern pearly-eye.
And the antennae on this individual seem ambiguous. They are mostly yellow (as in Southern), but have a slight tinge of dark (as in Northern). Hmm.
Eileen Schaeffer sent me this great shot of a hackberry emperor on her finger. This species loves to sup on salt and this individual is no exception: check out the unfurled proboscis.
Hackberry emperor slurping salt