Hypaurotis crysalus

The combination of vivid purple dorsal wings with black margins and orange marginal spots distinguishes adults from other North American hairstreaks. The gray ventral surface with white and brown striping provides camouflage when wings are closed at rest. The species is larger than most lycaenids. Males are territorial on oak trees, a behavior that can aid detection.

Wingspan 32–38 mm. Dorsal wing surface vivid purple with black margins, a black patch or band on the forewing, bright orange marginal spots, and delicate tail-like projections on the hindwings. Ventral surface dull gray with white and brown longitudinal stripes, small orange and blue accents. Larva yellowish-green, slug-like, and highly cryptic.

Montane oak scrubland dominated by Gambel's Oak (Quercus gambelii). Occurs at elevations approximately 6,500–7,500 ft. Butterflies favor healthy oak trees with minimal gall damage or other signs of weakness. South-facing slopes appear to be preferred.

Southwestern United States: Colorado, Utah, Arizona, New Mexico, southeastern Wyoming, and extreme eastern Nevada. Also recorded in northern Mexico. Type specimen collected at Palmer Lake, El Paso County, Colorado, in 1873.

Adults recorded from May to November, with peak abundance in July and August. One generation annually (univoltine). Eggs laid in late summer and fall overwinter on oak branches; larvae hatch to feed on new spring foliage.

Adults rarely visit flowers for nectar. Instead feed on: fermenting sap from tree wounds, exudates from developing acorns, and honeydew secreted by aphids and scale insects. Larvae feed exclusively on foliage of Gambel's Oak (Quercus gambelii).

• Quercus gambelii - host plantLarval food source; eggs laid on branches and twigs

Univoltine. Eggs laid individually on oak branches and twigs in late summer and fall, where they overwinter. Larvae emerge in spring to consume new oak foliage. Pupation details not documented in available sources. Adults emerge primarily July–August.

Males are territorial and defend individual oak trees from rival males, with chases observed on south-facing slopes. Adults normally rest with wings closed, revealing cryptic undersides. Bask with wings open to expose purple dorsal surface. Active even on cloudy days and until dusk; observed flying after thunderstorms.

Larval herbivore on Gambel's Oak. Adults may contribute to nutrient cycling through consumption of honeydew and sap exudates. Specific ecosystem functions beyond herbivory not documented.

Designated official state insect of Colorado in 1996. Sought after by butterfly watchers; described as elusive and difficult to locate despite locally abundant host plants. Subject of biological study regarding population biology and behavior. Type specimen historically significant to Colorado entomology.

• Other Lycaenidae hairstreaksSmaller size, different dorsal coloration (not vivid purple with black margins and orange spots), lack of territorial defense of oak trees
• Other purple butterflies (e.g., some fritillaries, brush-footed butterflies)Different wing shape, lack of tail-like hindwing projections, different habitat association with oak scrubland, flower-visiting behavior

• state insect
• montane
• oak-associated
• univoltine
• territorial males
• non-nectar feeding

• BugGuide
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Bug Eric: Colorado's State Insect: Colorado Hairstreak Butterfly
• The Interaction of Behavior, Population Biology, and Environment in Hypaurotis crysalus (Lepidoptera)