E-Fauna BC: Electronic Atlas of the Wildlife of British Columbia

Cercyonis oetus Scudder, 1875
Dark Wood Nymph; Woodnymphs
Family: Nymphalidae (Brushfoots)
Species account authors: Crispin Guppy and Jon Shepard.
Extracted from Butterflies of British Columbia
The Families of Lepidoptera of BC
Introduction to the Butterflies of BC
Photo of species

© Norbert Kondla  Email the photographer   (Photo ID #8086)

E-Fauna BC Static Map
Distribution of Cercyonis oetus in British Columbia
Details about map content are available here.

Species Information


Adult

Small Woodnymphs are small dark brown butterflies with small eyespots on the forewings. The front eyespot is distinctly larger than the rear one. The rear eyespot, and sometimes the front one as well, may be missing on the dorsal forewings. On the ventral forewings, there is no light band crossing the outer third of the wings, whereas in the other two woodnymphs there is always a definite but sometimes faint light band.

Immature Stages

For subspecies charon in Colorado, the eggs are lemon yellow, and barrel-shaped with 22 vertical ribs. First instar larvae are slender and taper towards the back, with two short "tails." The head is yellow brown, speckled with red brown, and the largest ocelli are emerald green. The body is pinkish yellow with red brown lines along the body, one down the middle of the back and four along each side. Mature larvae are cylindrical; they taper from the middle towards each end and have two short tails. The body is yellow green on the top half, more green on the bottom half. The tails are pale red, with yellow on the outer sides. Down the middle of the back is a dark green stripe bordered with yellow, and yellow lines on each side. The pupa is pale yellow green, thickly marked with whitish blotches on the underside. There is a whitish stripe down the middle of the back, and one on each side of the back. The wings have three streaks of darker green, and the edges of the wings, the top of the head, and the top of the thorax are lined with white. Pupal colour is highly variable in subspecies charon; others in the same batch were completely whitish green with no markings, greenish black with various markings, or dark brown with various markings (Edwards 1886b). The larvae and pupae are geographically variable in coloration (Emmel 1969).

Subspecies

Subspecies phocus (W.H. Edwards, 1874) (TL: Lac la Hache, BC) occurs in the Peace River, Chilcotin, northern Okanagan, Thompson, and Fraser drainages, and in the Kootenays and the Peace River. The ventral hindwings are smoothly dark brown, with the pattern present in subspecies oetus; TL: restricted to Mt. Judah, Placer Co., CA (Emmel et al. 1998a) only barely visible. There are a few small ventral submarginal spots. Intergrades with the nominate subspecies occur in the Similkameen Valley and the southern Okanagan, with the ventral hindwing a more medium brown, with a contrasting darker band across the middle. There is a thin, dark brown line on each side of the dark band that is sometimes missing on the basal side. A few small submarginal spots are present. Subspecies charon (W.H. Edwards, 1872) (TL: near Twin Lakes, Lake Co., CO) occurs at Flathead, BC.

Genus Description


The name Cercyonis is derived from Cercyon, the son of Poseidon (Opler and Krizek 1984). The common name "woodnymphs" was first used by Holland (1898) in reference to the butterflies' bouncy flight in generally open forest habitat, similar to nymphs bounding through open forests.

Woodnymphs are medium-sized, dark brown butterflies with prominent eyespots on the forewings and sometimes smaller eyespots on the hindwings. The eyespots are usually larger in females than in males, and are set in a lighter band. Woodnymphs have a peculiar bouncing flight, similar to that of ringlets.

Eggs are laid singly on grass blades. They are pale yellow, becoming tan and mottled with orange brown as they mature. They are cylindrical and squat, with a flat top and ridges down the side. First instar larvae are thinly covered with thick curved hairs, and are green with light and dark longitudinal stripes. Mature larvae are slender, green, or yellow green, with light and dark longitudinal stripes down the back and sides. They are thinly covered with hairs, and have two short red tails. Pupae are roughly cylindrical, rounded, and suspended from a cremaster. They are green to yellow green, and in most species have white or yellow markings (Emmel 1969).

Eggs hatch about 10 days after oviposition (at 25°C), and the first instar larvae immediately enter hibernation. By spring the larvae have shrunk to half their original length before they come out of hibernation. Once they commence feeding, they primarily feed at night. There are five (oetus, sthenele) or six (pegala) larval instars. It takes oetus about 2 months to pupate in the wild, and sthenele and pegala 2.5-3 months. Pupation occurs near the base of a grass clump, with the pupa hanging from grass blades. Adults emerge after about 20 days (EmmeI 1969).

Biology


Small Woodnymphs are univoltine and fly in June and July. There are five larval instars, and a female lays 100-150 eggs (Emmel 1969). Larvae hatch in the fall, and then hibernate without feeding. In spring they emerge from hibernation and begin feeding. Adults emerge about 10 weeks after the larvae come out of hibernation, and there is a prolonged emergence period spread over several weeks (Edwards 1886b).

Larvae feed on grasses, including bluegrass (Poa) species (Bird et al. 1995). Scott (1992) provides a list of oviposition substrates, but they have not been demonstrated to be larval foodplants.

Habitat


Small Wood nymphs are found in dry grassland, sagebrush, and open woodland areas across southern and central BC east of the Coast Ranges. They also occur in the Peace River.

Distribution

Distribution

Small Wood nymphs are found throughout the dry areas of western North America.

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)
COSEWIC
NativeS5YellowNot Listed
BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Additional Photo Sources

General References


Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2021. E-Fauna BC: Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [Accessed: 2024-07-17 9:01:38 PM]
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