9 Blue Butterflies: ID, Habitat, Host Plants & When to See Them

2025-10-30 10:15:40 6

At a glance: Blue butterflies owe their vivid color mostly to structural coloration—microscopic wing scales that reflect blue wavelengths. Below are 9 standout “blues,” each with how to identify, where to find, host plants, flight season, and conservation notes, plus field tips for watching and photographing them responsibly.

1) Blue Morpho (Morpho spp.)

Key ID: Dazzling electric blue upperside with black margin; underside brown with large eye spots. Huge: 13–18 cm (5–7 in) wingspan. Females duller.
Range & habitat: Lowland and foothill tropical forests of Central & South America; edges and light gaps.
Host & diet: Larvae on various host trees (often Fabaceae); adults feed on rotting fruit/sap.
When to see: Year-round in the tropics; most obvious on sunny late mornings.
Notes: Often rests with wings closed; the iconic “blue flash” appears during takeoff/glide.

2) Fender’s Blue (Icaricia icarioides fenderi)

Key ID: Male sky-blue upperside; female brown with white-rimmed spots; ~2.5 cm (1 in) wingspan.
Range & habitat: Willamette Valley, Oregon (USA)—open prairie remnants with lupines.
Host: Kincaid’s lupine (Lupinus oreganus)—critical for oviposition and larvae.
When to see: Spring to early summer (local).
Conservation: Endangered; recovery hinges on prairie restoration, lupine re-establishment, and invasive control.

3) Silvery Blue (Glaucopsyche lygdamus)

Key ID: Cool silvery-blue male upperside; neat black spots on underside; small size.
Range & habitat: Widespread in North American grasslands, barrens, and open sandy sites.
Host: Mostly Fabaceae (and regionally some Polygonaceae).
When to see: Single spring/early summer brood, usually May–June.
Notes: Best found around low floral patches in calm, sunny conditions.

4) Common Blue (Polyommatus icarus)

Key ID: Males vivid bright blue with narrow black border; females often brown with orange lunules and white fringe.
Range & habitat: Europe to Western Asia; tolerant of meadows, road verges, brownfields.
Host: Various clovers/medics (Fabaceae).
When to see: Multi-brooded late spring to autumn.
Notes: Communal roosting at dusk offers great photo opportunities.

5) Eastern Tailed-Blue (Cupido comyntas)

Key ID: Tiny tail filaments on hindwings; males blue, females grayish-blue; underside with clear black spots.
Range & habitat: North America, common in lawns, lots, edges, and weedy fields.
Host: Legumes (clovers, vetches, etc.).
When to see: Spring through summer (multiple broods).
Notes: Look for low nectar sources; approach slowly from behind and above.

6) Karner Blue (Plebejus samuelis)

Key ID: Males bright blue; females brown with bluish suffusion; ~2.5 cm (1 in).
Range & habitat: Northeastern & Upper Midwest USA—oak-pine barrens and sandy openings.
Host: Wild lupine (Lupinus perennis)—sole larval host.
When to see: Bivoltine (spring and summer flights).
Conservation: Endangered; success depends on keeping sites open, sunny, and lupine-rich via fire/grazing/mowing regimes.

7) Adonis Blue (Lysandra bellargus)

Key ID: Males an intense, ultra-clean sky blue with crisp white fringe; females brown.
Range & habitat: Southern Europe, tied to chalk/limestone grasslands.
Host: Typically horseshoe vetch (Hippocrepis comosa) and other Fabaceae.
When to see: Regional multi-brooded flights; numbers track grazing pressure and sward height.
Notes: Search warm, short-turf slopes with abundant flowers.

8) Boisduval’s Blue (Icaricia icarioides complex)

Key ID: Pale to bright powder-blue males with white fringe; females brown.
Range & habitat: Western USA—coastal dunes, foothills, and montane openings.
Host: Primarily lupines/legumes.
When to see: Spring–summer (local variation).
Notes: Often patrols along sunny south-facing edges and roadcuts.

9) Green-underside Blue (Glaucopsyche alexis)

Key ID: Male upperside blue; distinct green-tinted underside; females largely brown.
Range & habitat: Europe to Western/Central Asia in sunny flower-rich grasslands.
Host: Favours Fabaceae (varies locally).
When to see: Spring peak.
Notes: Side- or back-lighting brings out the green undersurface sheen.

Field Tips: Watch & Photograph Without Harm

Light: Early/late side-light enhances metallic blues; midday blows highlights.
Approach: Move slowly from rear/above while the butterfly is nectaring or basking.
Do no harm: Stay on paths, avoid trampling host plants (especially lupines), and don’t handle or net for photos.
Log useful data: Date, location, habitat, host plant, and clear dorsal/ventral shots help with ID and contribute to citizen-science databases.

Why “blue” looks so blue (quick science)

Most “blue” butterflies aren’t blue because of pigment. Their scales form micro-/nano-structures that selectively reflect blue light via interference and scattering—hence the vivid, angle-dependent “flash.”

Conservation: What actually helps

Habitat management: Keep grasslands open, sunny, and flower-rich with light grazing/mowing timed outside peak flights.
Host plant recovery: Re-establish lupine/clover belts; control shading invasive shrubs.
Community science: Share records to regional platforms with photos + host info to improve monitoring.

Quick Reference Table

Species	Signature Blue	Fast ID	Primary Hosts	Best Season
Blue Morpho	Electric, mirror-like blue	Huge; brown eye-spotted underside	Various trees (often Fabaceae)	Year-round (tropics)
Fender’s Blue	Sky-blue male	Tiny prairie blue; females brown-spotted	Kincaid’s lupine	Spring–early summer
Silvery Blue	Icy silvery male	Neat black underside spots	Legumes (some Polygonaceae)	Late spring–early summer
Common Blue	Bright sky blue male	Females brown with orange lunules	Clovers/medics	Late spring–autumn
Eastern Tailed-Blue	Blue/gray-blue	Hindwing tails	Legumes	Spring–summer
Karner Blue	Bright blue male	Two broods; sandy barrens	Wild lupine	Spring & summer
Adonis Blue	Intense pure sky blue	Chalk grassland specialist	Horseshoe vetch, etc.	Multi-brooded; regional
Boisduval’s Blue	Powder-blue male	White fringe; western USA	Lupines/legumes	Spring–summer
Green-underside Blue	Blue top, green bottom	Strong blue-green contrast	Fabaceae	Spring

animal tags： blue butterflies

We created this article in conjunction with AI technology, then made sure it was fact-checked and edited by a Animals Top editor.