Larvae of the North American genus Speyeria Scudder (some would argue Argynnis Fabricius, see Dunford 2009, de Moya 2016) are said to be very secretive, nocturnal feeders that subsist solely on Viola Linnaeus (Violaceae) (Scott 1986, Brock & Kaufman 2003, James & Nunnallee 2011, ad infinitum). Although a number of authors have, for example, either surmised (Bird et al. 1995¹), suggested (Durden 1965²), proposed (James 2012³), or observed (Christopher Durden pers. comm. 27 July 2005⁴) that other plant families could be/are used, no conclusive proof has ever been presented. Herewith I belatedly report finding five probable Speyeria mormonia mormonia Boisduval caterpillars feeding exclusively on Bistorta bistortoides Pursh (Polygonaceae) in a California arctic-alpine meadow, with all larvae reared to pupation and four parasitoid flies obtained. Thus, to the list of “Argynnis s.l.” that eat both Violaceae and Polygonaceae— currently only Argynnis aglaja Linnaeus (Fric et al. 2005, plus new Fukuda et al. 1983, Chou 1994, but see Nishida 1993[6])—previously overlooked Argynnis adippe Denis & Schiffermüller (Fukuda et al. 1983), Argynnis xipe Grum-Grshimailo (Lee 2005 fide Kim 1965), and now S. mormonia (this study) can be added. It will be interesting to note how these and future revelations of taxonomically unrelated foodplants affect our total-evidence understanding of the Argynnini and the phylogenetic placement of its genera.

On 4 July 1990, while on knees and elbows looking for Colias behrii W.H. Edwards (Pieridae) caterpillars to photograph at 3150 meters (10,335 feet) next to Middle Gaylor Lake, Tuolumne County, California, I encountered a last-instar Speyeria actively feeding on B. bistortoides (identified, verified, and accessioned at Jepson Herbarium, Berkeley, California, JEPS 84842 dated 28 July 1990). It crawled into the ground debris moments later, but was watched and then extricated; a careful check revealed no additional larvae. The time was about 12 noon PDT with a clear sky and pleasant temperature—a thorough examination of the vicinity disclosed zero violets. Seeing no other B. bistortoides nearby I left the area, only to return shortly to the same clump where yet another caterpillar in its penultimate stadium was discovered hiding among the tangled undergrowth.

Ten days later on 14 July 1990 I went back to the aforesaid alpine lakeshore for the sole purpose of finding more Speyeria preadults. Several hours of searching showed B. bistortoides to be abundant there, at least in places. However, leaves with only minor eaten damage were seen during this subsequent visit, inspection of which revealed no larvae. Just as a storm passed overhead in the early afternoon that would drop rain, hail, and the temperature, a patch with extensive fresh leaf incisions was finally found, which yielded a mature caterpillar resting on the bare ground next to the plant. Two weeks later on 28 July 1990 I again returned, this time circling the entire lake and checking every B. bistortoides for signs of recent feeding damage. In the seven hours so spent merely three such clumps were located, though many others exhibited older, scarred notches. From these promising plants, and with the aid of an iced tea spoon, two last-instar Speyeria were uncovered as they lay concealed at the base of two separate patches. Notably, the only other plant-eating insect encountered on all of the above B. bistortoides was a single sawfly (Hymenoptera) larva, plus still NO violets visible anywhere around Middle Gaylor Lake.

Fig. 1.

Probable Speyeria m. mormonia (final instar from 3150 meters, Middle Gaylor Lake, Tuolumne Co., CA; 6 July 1990, ∼16 mm in length, five days before pupation) on Bistorta bistortoides, a confirmed new hostplant record.

Thus, a total of five Speyeria caterpillars were found on four different B. bistortoides that were separated by considerable distances, the two closest clumps being roughly 24 meters (79 feet) apart and all on the same/east side of the lake. A couple of these plants were carefully uprooted and brought to my lab in Antioch where larval development continued (Fig. 1). In lieu of comprehensive testing, one of the caterpillars was simply confined for several hours on a small potted Viola ocellata Torrey & A. Gray, a shade-loving violet of the California Coast Ranges, upon which it extensively and repeatedly fed. All five Speyeria pupated successfully, one doing so in the soil, but none survived to adulthood due to misfortune (one) or tachinids (four), the latter a remarkable outcome given the highly furtive habits of these larvae. Of the four pupae confirmed to be parasitized, the ensuing dipteran(s) of one could not be located, while the remaining three chrysalises yielded a total of six maggots—three emerging from one pupa^†—and ultimately four adult flies, two males and two females, which were identified by Dr. Paul Arnaud (California Academy of Sciences, San Francisco, California, and donated thereto) as Madremyia saundersiiWilliston, a native tachinid with a wide range of primarily lepidopterous prey, including Speyeria cybele Fabricius (Arnaud 1978). One of the maggots emerged about five days after its host pupated, spending nine days as a pupa itself before producing a male, while the two female flies took approximately 12 days to eclose under equivalent ambient indoor, versus natural arctic-alpine, conditions.

Fig. 2.

Speyeria m. mormonia (final instar ex confined females from 2945 meters, Sonora Pass, Alpine Co., CA; 16 February 2003, 28 mm in length, several days before pupation) reared on Viola sororia Carl Ludwig Willdenow.

Although none of the above immature Speyeria resulted in an adult butterfly, the circumstantial determination of S. mormonia is nevertheless compelling for this otherwise well-studied taxon. A print from a larval slide was shown to caterpillar expert Thomas Allen (“with that dorsal stripe it looks very much like a Speyeria”, pers. comm. 13 March 1999) and Speyeria authority Dr. David James (“it certainly looks like mormonia”, pers. comm. 10 July 2015), and though Sierran butterfly expert Kenneth Davenport replied to my inquiry that “both egleis and mormonia should be there [lakeshore in question]” (pers. comm. 24 September 2014), photos of final-instar Speyeria egleis Behr in publications by James (2008) and James & Nunnallee (2011) illustrate a more uniformly patterned, darker, and larger larva. Additionally, albeit mindful of possible geographic, altitudinal, and/or individual variations, excellent matches for the subject California caterpillars—note distinctive combination of prominent middorsal pale stripe and whitish, relatively short scoli—can be seen in Miller & Hammond (2007, S. m. erinna W.H. Edwards, Oregon), James & Nunnallee (2011, S. m. washingtonia Barnes & McDunnough, Washington), Berwyn (2012, S. m. eurynome W.H. Edwards, Colorado), plus my own Kodachrome image of a last-stadium S. m. mormonia from neighboring Alpine County, California (Fig. 2). Furthermore, Guppy & Shepard (2001) state that “the larval habitat of the Mormon Fritillary occurs at higher elevations than that of other Speyeria species”, with Brock & Kaufman (2003) agreeing that S. mormonia is “often the only member of the greater fritillary group found at or above treeline”, while Dunford (2009) concludes that “Speyeria mormonia is the most likely member of Speyeria to occur in high mountain habitats.”

Having reviewed much of the relevant literature while preparing this paper, it is perhaps not completely surprising that S. mormonia, a widespread and abundant Western boreal butterfly that appears remarkably well adapted to many different mid-to-highelevation habitats, would eventually be documented to naturally utilize a hostplant other than Viola. Whether this represents a recent colonization (derived character) by just S. mormonia in North America or a wholly overlooked usage (ancestral character) shared with ecologically similar Nearctic congeners needs to be investigated by future workers.