Spilosoma pteridis

Edwards, 1875

brown tiger moth

Spilosoma pteridis, the brown tiger moth, is a small tiger moth in the Erebidae described by Henry Edwards in 1875. It is restricted to the Pacific Northwest region of North America, occurring in western Oregon and Washington, British Columbia, and northern Idaho. are active from late spring through early August and are associated with wet forest west of the Cascade Mountains. The has two recognized : the nominate S. p. pteridis and S. p. rubra.

Pronunciation

How to pronounce Spilosoma pteridis: /ˌspiːloʊˈsoʊmə ˈtɛrɪdɪs/

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Identification

Forewing length 11–13 mm. As a member of the tiger moth Spilosoma, it likely exhibits the characteristic pale or brownish ground coloration with dark spotting typical of the group, though specific diagnostic features distinguishing it from related Pacific Northwest Spilosoma are not detailed in available sources. The small size and restricted geographic range west of the Cascades help separate it from eastern North American .

Habitat

Wet forests west of the Cascade Mountains, including coastal rainforests, low elevation mixed hardwood-conifer forests, and higher elevation conifer forests in the Cascades.

Distribution

United States: western Oregon, western Washington, and northern Idaho; Canada: British Columbia. GBIF records also indicate presence in Alberta, Manitoba, and Saskatchewan, though these may represent vagrant occurrences or require verification.

Seasonality

on wing from late spring to early August.

Diet

Larvae probably feed on various herbaceous plants; specific plants not documented.

Similar Taxa

  • Spilosoma virginicaYellow bear overlaps in tiger moth characteristics but occurs in eastern North America; distinguished by geography and larval coloration (yellow to orange with variable black markings versus brown tones of S. pteridis).
  • Spilosoma congruaAgreeable tiger moth is another small Spilosoma with overlapping western range; separation requires examination of genitalia and detailed wing pattern differences not readily summarized in general sources.

Sources and further reading