For folks who live in Florida, Southern Texas, and below Tuscon, Arizona, your pipevine plants may be visited by two different swallowtail butterflies. This can cause a problem because most plants that Pipevine Swallowtail caterpillars can safely eat will kill Polydamas Swallowtail caterpillars and vice versa. Click on this sentence for a partial list of plants that are safe for each species.
When eggs are laid on pipevine, they will be one of three colors. First, Pipevine swallowtail eggs are burgundy/red. Polydamas Swallowtail eggs are yellow/gold. Lastly, sometimes Long-tailed Skippers will lay eggs on pipevine, especially woolly pipevine, but their offspring will die unless they are moved immediately to their actual host plant.
When we check our pipevine plants and see caterpillars, we may not be able to differentiate between the two species of caterpillars. The clue to their identity is simple. Although both Pipevine Swallowtail and Polydamas Swallowtail caterpillars have a gold/yellow line at the top of their heads, Polydamas caterpillars have that gold line across the entire top of their heads and part-way up their filaments.
Once they have pupated, they are so similar that people often need both species together to differentiate between the two. Polydamas Swallowtail chrysalises have a more prominent raised band at the top of their thoraxes.
In addition, Pipevine Swallowtail green chrysalises are a little more yellow than Polydamas Swallowtail green chrysalises.
I will soon take side-by-side photos of brown chrysalises of the two species to replace the two photos above.