Macaria occiduaria

Distinguished from similar Macaria species by the combination of broad, well-defined dark transverse lines on the forewings and the relatively uniform gray ground color without strong brown or orange tints. Macaria signaria (Dotted Gray) has more distinct discal spots and finer lines. Macaria bisignata (Red-lined Gray) shows reddish-brown tones and different line patterns. Genitalia examination may be required for definitive identification of worn specimens.

Adults have gray forewings with two prominent dark transverse lines: a basal line and a postmedian line, often with a darker median shade between them. The hindwings are paler gray with fainter transverse lines. Wingspan approximately 25–30 mm. Antennae are filiform. The overall coloration is muted gray with subtle brownish or purplish tints in fresh specimens.

Occurs in forested and woodland habitats, particularly coniferous and mixed forests. Associated with pine and fir woodlands in western mountain ranges. Elevation range extends from low foothills to subalpine zones.

Western North America: documented from British Columbia south through the Pacific states to California, and eastward to the Rocky Mountain states including Montana, Idaho, Wyoming, Colorado, and New Mexico.

Adults have been observed from late May through August, with peak activity in June and July. Single-brooded.

Complete metamorphosis with egg, larva, pupa, and adult stages. Larval host plants are suspected to include conifers (Pinaceae), particularly species of Pinus, based on related Macaria species, but specific documentation for M. occiduaria is limited.

Adults are nocturnal and attracted to light. Larvae are likely twig mimics, resting with body extended along conifer needles or twigs.

Larvae function as folivores on coniferous trees, contributing to nutrient cycling in forest ecosystems. Adult moths serve as prey for nocturnal insectivores including bats and night-foraging birds.

No significant economic importance. Occasionally encountered by forest entomologists and moth enthusiasts. Not considered a forest pest.

• Macaria signariaSimilar gray coloration and wing pattern, but M. signaria has more prominent discal spots and finer, more irregular transverse lines.
• Macaria bisignataOverlapping range, but M. bisignata displays reddish-brown wing coloration and different transverse line configuration.
• Iridopsis speciesSome Iridopsis species share gray coloration and transverse lines, but differ in wing shape (more triangular in Iridopsis) and genitalia structure.

• geometridae
• ennominae
• macariini
• western north america
• coniferous forest
• nocturnal
• summer-flying

• BugGuide
• GBIF taxonomy match
• iNaturalist taxon