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Montana Field Guide

Montana Field Guides

Small Wood Nymph - Cercyonis oetus


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 1.9-2.4 cm. Dark brown overall. Uppersurface of forewing with two eyespots, lower eyespot smaller and closer to outer margin than larger upper eyespot (male with extensive dark sex patch, only upper eyespot usually present); undersurface of forewing usually lacking postmedian dark line (if present, basal to the top eyespot), hindwing with postmedian darkline strongly projecting inward in center, postmedian eyespots absent or weakly developed.

Phenology
One flight; late June to August (Scott 1986). Mainly June to August, but to late September in some areas (Glassberg 2001). Late May to late September in Washington and Oregon (Pyle 2002), late May to mid-August in Washington (James and Nunnallee 2011), late May to mid-September in Oregon (Warren 2005), June and July in British Columbia (Guppy and Shepard 2001).

Diagnostic Characteristics
Best determined by a combination of forewing with two eyespots, lower eyespot smaller and closer to outer margin than upper eyespot, undersurface of forewing usually lacking postmedian dark line (if present, basal to the top eyespot), undersurface of hindwing with postmedian darkline strongly projecting inward in center.

Species Range
Montana Range

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Range Comments
Throughout much of the intermountain West and Rocky Mountain front east of the Cascades and Sierra Nevada crest, from central British Columbia south to central California and east to southern Saskatchewan, the far western Dakotas, northwestern Nebraska, eastern Colorado, central New Mexico (Scott 1986; Opler and Wright 1999; Glassberg 2001); often between 1525 m and 3200 m elevation in Colorado (Brown 1957; Ferris and Brown 1981), between 245 m and 2286 m elevation in Oregon (Warren 2005). In Montana, reported across the state from most counties (Kohler 1980; Stanford and Opler 1993). Common to abundant (Glassberg 2001).

Summary of Observations Submitted for Montana
Number of Observations: 17

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Relative Density

Recency

 

(Observations spanning multiple months or years are excluded from time charts)



Migration
Non-migratory.

Habitat
Open arid brushland, chaparral, sagebrush steppe, high plains, foothills, open woodlands, montane meadows, on occasion above treeline in alpine terrain (Ferris and Brown 1981; Scott 1986; Opler and Wright 1999; Glassberg 2001; Guppy and Shepard 2001; Pyle 2002). In Glacier National Park, Montana reported in montane xeric meadows (Debinski 1993); in the Montana portion ot the Greater Yellowstone Ecosystem, most abundant in meadows dominated by sagebrush and grass (Debinski et al. 2013).

Food Habits
Larval food plants include the grasses Festuca and Poa, probably Koeleria; Elytrigia in captivity (Scott 1992; Guppy and Shepard 2001; James and Nunnallee 2011). Adults feed on flower nectar (including Achillea, Anaphalis, Apocynum, Arnica, Berteroa, Ceanothus, Centaurea, Chrysothamnus, Cirsium, Carduus, Clematis, Erigeron, Erioganum, Geranium, Grindelia, Gutierrezia, Heterotheca, Medicago, Melilotus, Mentha, Monarda, Potentilla, Rudbeckia, Senecio, Solidago, Symphyotrichum, Tetradymia, Viguira), mud, dung, and carrion (Pyle 2002; James and Nunnallee 2011; Scott 2014).

Reproductive Characteristics
Females lay eggs (100-150) singly, often on undersides of dried grass blades, in litter, or on nearby plants; 10 cm above ground surface (Emmel 1969; Scott 1986, 1992). Eggs hatch in about 14 days; L1 instars hibernate (overwinter) in groups. Development fairly rapid after breaking diapause, reaching L5 instar and pupation in about 55 days (depending on temperature). Adults eclose (emerge from pupae) in about 18 days. Larvae do not build nest, feed on edges of grass blades mostly at night, are gregarious. Pupae attached to grass stems or blades, adjacent blades pulled down with silk to form slight protective tent; sometimes pupae attached to underside of forb leaf (Emmel 1969; Scott 1979, 1992; James and Nunnallee 2011). Males patrol throughout the day in open and grassy areas, regardless of topography, seeking females (Scott 1975b, 1986).

References
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Citation for data on this website:
Small Wood Nymph — Cercyonis oetus.  Montana Field Guide.  .  Retrieved on , from