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Compton Tortoiseshell - Nymphalis l-album


Global Rank: G5
State Rank: S5

Agency Status
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General Description
[From Ferris and Brown 1981, Scott 1986, Glassberg 2001, Guppy and Shepard 2001, Pyle 2002) Forewing 3.3-3.6 cm. The largest of our true nymphs. Wings broad and irregular in outline; inner margin of forewing straight (not curved); dorsal surface rich rusty with large submarginal yellow spots and heavily blotched with large black spots, single white spots on costal margins of forewings and hindwings; ventral surfaces shades of brown, gray and tan, striated and dotted, darker on inner half and white-frosted on outer half, hindwing with central small silver comma mark.

Phenology
One flight; mid-July to early August, the adults hibernate then emerge in spring (April and May) and lay eggs (Scott 1986); early March to mid-October in Oregon and Washington (Pyle 2002), with peaks in April and August reflecting the flights of old and new females, respectively.

Diagnostic Characteristics
The single white spots on costal margins of forewings and hindwings, and ventral hindwing with central small silver comma mark distinguish this species from the similar California Tortoiseshell (Nymphalis californica) and other tortoiseshells as well as the smaller anglewings (Polygonia).

Species Range
Montana Range

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Range Comments
In North America, resident from Alaska panhandle and northern British Columbia south to northern Washington, Idaho, and northwestern Montana, east across boreal Canada and northeastern US to the Atlantic Coast. During outbreak years may occur far south and north of the normal range, including to central Colorado, across the northern Great Plains and into the Arctic (Scott 1986, Guppy and Shepard 2001). In Montana, resident in the northwest, possibly resident in the Greater Yellowstone Ecosystem, with scattered records in the eastern plains (Kohler 1980, Debinski 1993, Stanford and Opler 1993, Debinski and Pritchard 2002).

Migration
Migratory, with periodic outbreak years when large numbers occur outside the normal range (Scott 1986, Glassberg 2001, Guppy and Shepard 2001, James and Nunnallee 2011).

Habitat
Deciduous woodlands, riparian woodlands, moist canyons, boreal woodland clearings (including logging roads) (Scott 1986, Guppy and Shepard 2001, Pyle 2002). In Glacier National Park, reported from mesic meadows and woodlands (Debinski 1993).

Food Habits
Larval food plants include birches (Betula), elm (Ulmus), willow (Salix) and aspen (Populus); possibly also Humulus and Malus. Adults feed on sap, rotting fruit, mud, and occasionally flower nectar (Ferris and Brown 1981, Scott 1986, Guppy and Shepard 2001, Pyle 2002, James and Nunnallee 2011).

Reproductive Characteristics
Adult females probably begin laying shortly after emergence from hibernation, in April and May. Eggs laid on lower branches of host plant near tip with green unopened leaf buds; eggs laid in clusters of up to 36 eggs. Larval development occupies about 35 days (depending on temperature), with 4, 5, 4, 5, and 17 days spent in L1-L5 instars, respectively. No nests or shelters constructed but larvae are gregarious. Adults emerge from pupae (eclose) in about 16 days (James and Nunnallee 2011).

References
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Citation for data on this website:
Compton Tortoiseshell — Nymphalis l-album.  Montana Field Guide.  .  Retrieved on , from