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Montana Field Guides

Northwestern Fritillary - Speyeria hesperis


Global Rank: G5
State Rank: S5

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General Description
[From Ferris and Brown 1981; Scott 1986; Opler and Wright 1999; Glassberg 2001; Pyle 2002] Forewing 2.2-3.2 cm. Forewing pointed in some populations. Eyes blue-gray. Uppersurface of forewing borders usually black, males with swollen black areas along forewing veins; undersurface of hindwing fairly evenly colored red-brown to orange-brown basal disk, spots either silvered or unsilvered.

Phenology
One flight; late June to August (Scott 1986), mid-June to mid-September (Glassberg 2001). Mid-June to early September in Oregon and Washington (Pyle 2002; Warren 2005); late June to early August in British Columbia (Guppy and Shepard 2001).

Diagnostic Characteristics
Best determined by the uppersurface forewing border usually black; undersurface of hindwing basal disk fairly evenly colored red-brown to orange-brown, spots either silvered or unsilvered; eyes blue-gray.

Species Range
Montana Range

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Range Comments
Alaska, central Yukon, southwestern Northwest Territories (MacKenzie River drainage) south in the Cascades and Sierra Nevada to central California, in the Rocky Mountains to central Arizona and southern New Mexico, east to southwestern Manitoba; also the Black Hills, South Dakota (Opler and Wright 1999): to 2440 m elevation in Oregon (Warren 2005), to 3260 m elevation in Colorado (Brown 1957; Scott and Scott 1978). In Montana, probably reported from the western 2/3 of the state (Kohler 1980; Stanford and Opler 1993), but needs review due to contentious taxonomy with S. atlantis, with which it was formerly included (Warren 2005). Mainly common to abundant (Glassberg 2001).

Migration
Non-migratory.

Habitat
Moist and mesic montane meadows, forests, gulches, along creeks, valley bottoms (Scott and Scott 1978; Scott 1986; Opler and Wright 1999; Glassberg 2001; Guppy and Shepard 2001; Pyle 2002; Warren 2005). In Glacier National Park, Montana reported from xeric and mesic montane meadows (Debinski 1993).

Food Habits
Larval food plants include several species of Viola (Scott 1986, 1992, 2006; Warren 2005; James and Nunnallee 2011). Adults feed on flower nectar (including Achillea, Agastache, Agoseris, Anaphalis, Anemone, Apocynum, Arctium, Arnica, Asclepias, Buddleia, Carduus, Ceanothus, Centaurea, Chrysothamnus, Cirsium, Clematis, Conium, Dipsacus, Erigeron, Erioganum, Euphorbia, Gaillardia, Geranium, Grindelia, Haplopappus, Heracleum, Heterotheca, Holodiscus, Jamesia, Liatris, Monarda, Nepeta, Physocarpus, Prunus, Rhus, Rudbeckia, Sedum, Senecio, Solidago, Symphoricarpos, Symphyotrichum, Taraxacum, Trifolium, Viguiera), tree sap, dung, and mud (Scott 1986, 2014).

Reproductive Characteristics
Females lay eggs eggs singly and haphazardly in shaded litter on the undersides of dried leaves, pine needles, stems, other debris near host plant (Scott 1986, 1992, 2006). Eggs hatch in 5-18 days (depending on temperature), L1 instars overwinter (diapause) without feeding. Development after diapause to L6 instar and pupation takes about 22 days, another 17 days to adult emergence from pupae (eclosion). Larvae nocturnal, build no nest (Scott 1986; James and Nunnallee 2011). Males patrol throughout the day in open areas, especially moist valley bottoms and along streams, in search of females (Scott 1975b, 1986).

References
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Citation for data on this website:
Northwestern Fritillary — Speyeria hesperis.  Montana Field Guide.  .  Retrieved on , from