Vasu Dev,* Bill Ly, Art E. Miranda and Wayne Whaley

Abstract: The female Indra Swallowtail butterfly lays eggs on a number of species of the genus Lomatium in the Apiaceae family. The essential oils of three varieties of Lomatium grayi; L. grayi. var. grayi, L. grayi var. depauperatum and L. grayi. var. (undescribed) have been analyzed. Among the major components, L. grayi var. grayi shows myrcene (8.4%), β-phellandrene/limonene (27.2%), γ-terpinene (10.4%), and senkyunolide (24.4%). L. grayi var. depauperatum shows myrcene (8.1%), p-cymene (4.3%), β-phellandrene/limonene (20.8%), (Z)-β- and (Ε)−β−ocimene (23.6%), γ-terpinene (4.4%), germacrene D (4.6%), senkyunolide (4.7%), and (Z)-ligustilide (6.7%). L. grayi (new varity) shows β-phellandrene/limonene (17.7%), γ−terpinene (16.1%), and senkyunolide (44.0%). These observations contrast significantly with the reported composition of L. grayi. Only L. grayi var. depauperatum and L. grayi (new variety) attract the butterfly.

The Indra Swallowtail butterfly (Papilio indra; Papilionidae) is restricted to 13 western states (1). It has been observed to prefer laying eggs on 21 species of the huge family Apiaceae (>300 species in western U.S.), 12 of which are in genus Lomatium (2). Its sympatric relative, Papilio zelicaon, is known to use 58 species from this family. This attraction of the Indra Swallowtail to a few apiaceous species is thought to be attributed to the piney and lemony aromas inherent in most of them (2), but this does not appear to be the case for P. zelicaon whose host plants often do not share these aromatic attributes. It is interesting that several members of genus Papilio also use plants in family Rutaceae which contains similar secondary plant compounds and aromas (3,4). The essential oil from the fruits of one of the Lomatium species, L. macrocarpum, which attracts the Indra Swallowtail butterfly, has been reported to contain nearly 79% of α- pinenes and β-pinenes (5). Lomatium grayi occurs in three varieties, L. grayi var. grayi, L. grayi var. depauperatum and L. grayi var. (new variety, in prep.). Interestingly, L. grayi var. grayi is not used by Indra Swallowtail butterflies to lay eggs even though both occur together at many locations across the butterfly range. Preliminary laboratory rearing indicates that the native populations of the butterfly that use the two L. grayi varieties (depauperatum and new variety) are the only ones capable of doing so (Whaley: personal observations). Our continued interest in the chemosystematics of the genus Lomatium (6), and a desire to determine if there are significant differences among the essential oil components of L. grayi var. depauperatum and L. grayi (new variety) on the one hand and L. grayi var. grayi on the other that could explain the differences in egg deposition behavior of the butterfly towards the three varieties of this specie has led to the present investigation. This is the first of several reports dealing with the analyses of the Indra Swallowtail butterfly’s larval host plants in an attempt to reveal the essential oil common denominators and/or differences amongst them.