Papilio indra pergamus

Edwards' Swallowtail

The subspecies of the rarely-encountered Indra swallowtail from the San Gabriel Mountains down to the mountains of Riverside and San Diego Counties is pergamus. As of 2021, I've seen it a few times in the San Gabriels hilltopping on Sunset Peak; in the San Jacintos near Idyllwild patrolling a high ridge; and at Kwaaymii Point in Anza-Borrego. The type locality was established by Scott Miller in the 1980s as "Devil Canyon, about 11 km NNW of San Bernardino, San Bernardino Mountains, San Bernardino County, California, a well known locality for the subspecies (Emmel, pers. comm.)." I've reproduced his article below as well as Edwards' description of pergamus.

This butterfly is a hilltopper, but it is best to look just below the actual hilltops and along ridges to find indra. The southwestern side of the hill is usually the best place to look. They fly in the spring, and the larvae feed on aromatic Apiaceae family plants, especially Tauschia arguta, T. parishii, and Lomatium lucidum.

'Edwards' Indra Swallowtail - Papilio indra pergamus
Papilio indra pergamus taking nectar atop Sunset Peak in the San Gabriel Mountains. May 22, 2007.
'Edwards' Indra Swallowtail - Papilio indra pergamus
The same individual.
'Edwards' Indra Swallowtail - Papilio indra pergamus
This Papilio indra pergamus was patrolling a ridgeline along Keen Camp Summit road in the San Jacintos. April 24, 2021.
Tauschia arguta, larval food plant of the Indra Swallowtail - Papilio indra pergamus
Tauschia arguta, southern tauschia, is the main host plant of indra pergamus where I've seen it. It's an aromatic herb in the Apiaceae (carrot) family. Other members of this family that pergamus is known to use are Tauschia parishii and Lomatium lucidum.
Tauschia arguta and Tauschi parishii leaves comparison
Tauschia parishii, left, has leaves that are easily distinguished from those of Tauschia arguta, on the right.
Original description of Papilio indra pergamus
Henry Edwards' description of what became subspecies pergamus from 1874. The journal is Proceedings of the California Academy of Sciences.
Paper on the true type locality of Papilio indra pergamus
This paper by Scott Miller from 1984 fixed the type locality to a known locality for pergamus. Devil Canyon is west of highway 18 below Crestline.

©Dennis Walker