Undersides of adult eastern tailed-blues are pale gray with numerous small dark spots. Both sides of the hindwings have 2 (occasionally 1 or 3) orange spots by the thin tail. Males are blue above, while the upper side of females is a mixture of blue and dark gray with blue predominant in the spring and dark gray predominant later.
Larvae are downy, green or brown, with a darker brown line along the top and oblique (slanted) brown lines along the sides, and with a small, black head.
Similar species: Azures and the other blues in Missouri do not have tails on the hindwings. Hairstreaks have hindwing tails, but they also have banding on the undersides of the wings.
Wingspan: ½–1 inch.
Habitat and Conservation
Very common in prairies, fields, empty lots, roadsides, and residential yards. Can be found in nearly any open, sunny habitat. Typically flies close to the ground.
Larvae feed on flowers, seeds, and occasionally the leaves of many types of clovers, alfalfa, vetch, and other members of the Fabaceae (the pea or bean family). The commonness of these plants helps explain why this butterfly is so widespread. Adults drink nectar from a variety of flowers, particularly ones low to the ground and with short floral tubes.
Adults fly from the end of March into early November. There are three broods. Males patrol for females and carry the female when mated pairs are disturbed. Females deposit eggs singly on flowers and leaves of a suitable host plant. Caterpillars hatch and burrow into pods to feed on seeds. Full-grown caterpillars overwinter in seedpods and pupate in the spring. The adults’ tendency to fly within inches of the ground limits their nectar visits and egg-laying sites to low plants. They spend the night in the places where they basked in the late sunlight.
This butterfly is attractive, dainty, and very common — but few Missourians could tell you its name. Learning about the eastern tailed-blue puts you into a special category of people who love nature!
The caterpillars are herbivores that graze on vegetation. They secrete a substance that is attractive to certain types of ants, and these ants help protect the larvae from predators.
The thin, antennae-like tails on the hindwings can fool potential predators, such as birds and jumping spiders, into snapping at the hindwings, which are less valuable to the butterfly than its head.