Arctia caja

Distinguished from similar tiger moths by the combination of brown forewings with cream bands and bright orange hindwings with blue-black spots. Males have weakly pectinate (comb-like) antennae, while females have thread-like filiform antennae. The hindwing pattern of large rounded bluish spots on orange background is diagnostic. Similar species include other Arctia, but A. caja is larger and has the distinctive blue-spotted orange hindwings.

Open forests, clearings, forest edges and hedgerows, roadsides, extensive dry or wet grasslands, and occasionally gardens. Found from lowland plains to over 2,300 m elevation. Prefers seasonal and temperate environments with sufficient ground vegetation for larval development.

Holarctic distribution. In Europe: from Spain through western and central Europe to eastern Asia and Japan; north to Scandinavia, south to southern Italy, the Peloponnese, Asia Minor, and the Himalayas. In North America: boreal belt and cordilleras of western North America.

Univoltine. Most adults observed from mid-June to mid-August. Adults fly at night. Caterpillars hibernate through winter while still small (<10 mm), resuming feeding in spring.

Caterpillars are extremely polyphagous, feeding on a wide range of low-growing plants and shrubs including Rumex, Rubus, Urtica, Lonicera, and Salix.

Eggs laid in flat plates on undersides of host plant leaves. Caterpillars hibernate in ground vegetation while small (<10 mm). Pupation occurs in a silk web woven on the ground. Adults emerge in summer and are nocturnal.

Nocturnal flight activity. Aposematic coloration serves as warning to predators; the species sequesters toxic alkaloids from host plants. Adults do not feed.

Subject of long-term population studies in the U.K. documenting 85% decline over 30 years. Genome sequenced as part of biodiversity research. Caterpillars occasionally encountered by gardeners but not considered a pest.

• Arctia virginalisSimilar common name (Ranchman's tiger moth) and larval form (woolly bear caterpillar), but restricted to western North America with different wing patterns and habitat preferences.
• Other Arctia speciesGenerally smaller or with different hindwing coloration; A. caja is distinguished by its large size and distinctive orange hindwings with blue-black spots.

• aposematic
• alkaloid sequestration
• population decline
• genetic diversity loss
• phenotypic change
• climate change response
• genome sequenced

• BugGuide
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Rick Karban and the Wooly Bear Caterpillars of Bodega Bay | Bug Squad
• UCF student names a new frog species after her professor | Blog
• Nota Lepidopterologica | Blog - Part 2
• endoparasitoid | Blog
• Long-term decline in abundance and distribution of the garden tiger moth ( Arctia caja ) in Great Britain
• Phenotypic changes and reduced genetic diversity have accompanied the rapid decline of the garden tiger moth ( Arctia caja ) in the U.K.
• The genome sequence of the Garden Tiger, Arctia caja (Linnaeus, 1758) (Lepidoptera: Erebidae).