Blues (Polyommatinae) — identification, habitat & look-alikes

Blues are a group of small butterflies found in lawns, meadows, and open woodland across the United States. Males of many species have blue upper wings, while females are often brown and some species are mostly brown. Some species are widespread, while others occur only in small areas tied to a single caterpillar food plant.

In this group

Eastern Tailed-BlueCupido comyntas

Common in open areas across much of the eastern United States, it has two tiny tails and orange marks on the hindwings.

Spring AzureCelastrina ladon

This pale blue appears early in spring in the eastern United States. Its lightly marked gray underside helps separate it from darker-spotted blues.

Melissa BluePlebejus melissa

A western blue with an orange row near the hindwing edge; males are blue above and females are mainly brown.

Boisduval's BlueIcaricia icarioides

A western species linked to lupines, it is best recognized with both the upper and lower wing surfaces in view.

Silvery BlueGlaucopsyche lygdamus

Found widely across northern and western regions, it has a pale silvery underside with a neat row of black spots.

Appearance

Appearance: Check the underside for spot placement, orange edge marks, and tiny tails. Those details are usually more dependable than how blue the upper wings look in changing light.
How to recognize it: These are usually small, slim butterflies with blue or brown upper wings and rows of fine dark spots on a gray or tan underside. Males are blue in many species, while females are often brown with only a dusting of blue.

Look-alikes

HairstreaksTheclinae

Hairstreaks often show stronger lines below and more obvious hindwing tails. Some blues also have tails, so compare the full underside pattern instead of relying on that feature alone.

Why they get mixed upBoth are small gossamer-winged butterflies, and both can flash blue.

CoppersLycaeninae

Coppers usually have stronger orange or copper coloring above. Blues more often have blue males and fine black spotting on a pale underside.

Why they get mixed upBoth are small members of Lycaenidae with spotted wing undersides.

Where it lives

Typical habitats: meadows and prairies
roadsides and gardens
open woodland
Range: Blues occur across the United States, but individual species can be eastern, western, northern, southern, or extremely local. Eastern Tailed-Blues are widespread in the East, while Boisduval's Blues and many related blues are western.
Preferred conditions: Sunny places with low flowers and the right caterpillar are the best places to look. Damp soil may attract groups of males seeking water and minerals.

Behavior

Diet: Adults usually sip flower nectar. Most caterpillars eat the flowers, fruit, or leaves of particular plants, though some blues later obtain food from ants.
Activity: Adults fly low over vegetation, visit small flowers, and sometimes gather on damp ground. Males of some species patrol around the host plants while looking for females.
Overwintering: The overwintering stage varies by species and region. Eggs, partly grown caterpillars, and are all used within the group.

Life cycle

Larva: The caterpillars are short and slug-shaped. In many species, ants collect sugary secretions from a caterpillar and protect it from enemies.
Caterpillar food plants: Most caterpillars eat a limited set of host plants. Many U.S. blues use members of the pea family, but the exact plant differs by species.

Name and classification

About the name: Eastern Tailed-Blue (Cupido comyntas) is also called Everes comyntas. Boisduval’s Blue (Icaricia icarioides) was formerly called Plebejus icarioides.
Group name: Blues is the standard English group name for Polyommatinae, a subfamily of the gossamer-winged butterflies. The name describes the males of many species, not every individual in the group.

Conservation

Conservation: In the United States, the Karner Blue is federally endangered.