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Montana Field Guide

Montana Field Guides

Sylvan Hairstreak - Satyrium sylvinus


Global Rank: G5
State Rank: S4

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General Description
[From Ferris and Brown 1981; Scott 1986; Opler and Wright 1999; Glassberg 2001; Pyle 2002] Forewing 1.4-1.6 cm. With or without a tail (tailed in Montana). Uppersurface pale gray to brownish-gray with a bluish sheen when fresh, slight spotting of dull orange near hindwing edge; undersurface gray to brownish-gray with a postmedian row of small round white-ringed black spots, blue tail spot on hindwing lacks orange cap, a small marginal orange patch (or two) just anterior to tail spot near outer angle.

Phenology
One flight; May to June at low elevations in California, mid-July to mid-August at higher elevations and northward (Scott 1986). Late May to mid-July at lower elevations, July to mid-September at higher elevation and northward (Glassberg 2001). Early July to mid-August in Colorado (Scott and Scott 1978), Early May to early September in Oregon and Washington (Pyle 2002), mid-May to early August in Oregon (Warren 2005), mainly late June to mid-August in British Columbia (Guppy and Shepard 2001).

Diagnostic Characteristics
Best determined by a combination of uppersurface pale gray to brownish-gray with slight spotting of dull orange near hindwing edge, undersurface gray to brownish-gray with a postmedian row of small round white-ringed black spots, blue tail spot on hindwing lacks orange cap, a marginal orange patch just anterior to blue tail spot.

Species Range
Montana Range

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Range Comments
Southern British Columbia and western Montana south to northern Baja California, southern Arizona, and central New Mexico (Scott 1986; Opler and Wright 1999; Glassberg 2001); 1830 m to 2440 m elevation in the Rocky Mountain states (Ferris and Brown 1981), 1570 m to 2560 m elevation in Colorado (Brown 1957; Scott and Scott 1978), 91 m to 2195 m elevation in Oregon (Warren 2005). In Montana, reported from 14 counties in the western 1/3 of the state, the majority west of the continental divide (Kohler 1980, Stanford and Opler 1993; FLMNH Lepidopterists' Society database). Locally uncommon to locally common (Glassberg 2001).

Summary of Observations Submitted for Montana
Number of Observations: 2

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Relative Density

Recency

 

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



Migration
Non-migratory.

Habitat
Willow-lined streamsides, ditches, marshes, foothill meadows, canyons, valley bottoms (Ferris and Brown 1981; Austin 1985; Scott 1986; Opler and Wright 1999; Glassberg 2001; Pyle 2002). Habitat in Montana generally not described but probably similar; valley bottom willow-bog reported in 2012 (Butterflies and Moths of North America database).

Food Habits
Larval food plants include several species of Salix (Emmel and Emmel 1968; Ferris and Brown 1981; Scott 1986, 1992, 2006; Guppy and Shepard 2001; James and Nunnallee 2011). Adults feed on flower nectar (including Aesculus, Allium, Anaphalis, Apocynum, Asclepias, Brassica, Carduus, Centaurea, Cirsium, Clematis, Eriogonum, Melilotus, Rudbeckia) and mud (Warren 2005; James and Nunnallee 2011; Scott 2014).

Reproductive Characteristics
Females lay eggs singly, or in small clusters of 3-4 glued together, in small holes and crevices on host plant twigs and stems; eggs overwinter (Emmel and Emmel 1968; Scott 1979, 1986, 1992; James and Nunnallee 2011). Eggs hatch 3-6 days after exiting diapause (depending on temperature). Develop to L4 instar and pupate about 32-40 days post egg-hatch, adults eclose (emerge from pupae) in about 12 days (James and Nunnallee 2011). Larvae feed on leaves, build no nest, may aggregate during day in small groups on leaf undersurface, feed nocturnally and diurnally, are tended by ants in captivity (Formica pilicornis), larger larvae may cannibalize smaller ones, pupate on host plant (Scott 1986; Ballmer and Pratt 1991; James and Nunnallee 2011). Males perch from mid-morning to mid-afternoon on low vegetation near host plants in wet areas in wait of females, seldom patrol in search of females (Emmel and Emmel 1968; Scott 1975b, 1986).

References
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Citation for data on this website:
Sylvan Hairstreak — Satyrium sylvinus.  Montana Field Guide.  .  Retrieved on , from