Edwards' Hairstreak

Endemic to the Eastern United States.

WSU Vancouver

June 10, 2022

Geography

Range Map

Edwards' hairstreak (Satyrium edwardsi) resides in the eastern half of the United States and Southern Canada.

The butterfly may be extirpated from the Great Plains portion of the range, and some states in the Southern end of the range.

Study area

For this study, we evaluated populations in New Hampshire.

Our data comes from the National Guard Army Pembroke Training Institute.

Natural History

Species interactions

Host Plant

Edwards' hairstreak's host plant is oaks (Quercus spp.) and in the eastern range they use scrub oak (Q. ilicifolia), white oak (Q. alba), and others.

Nectar Plants

This butterfly is a nectar generalist, seen feeding on milkweeds (Asclepias spp.), dogbane (Apocynum cannabinum), goldenrods (Solidago spp.), and clover (Melilotus spp.).

Other species

Larger caterpillars spend their days in ant nests at the base of host trees providing them with honeydew they produce for the protection from predators.

Habitat

Edwards' hairstreak needs both oak thickets, for its hostplant, and meadows, for nectar. They are found in oak savannah, sand barrens, and limestone ridges. They may require ant nests at the base of trees to care for caterpillars, and this interaction will only occur with certain species of ants.

Population Dynamics

The populations of Edwards' hairstreak today are fragmented, especially in the Atlantic Coastal states.
Population sizes are believed to be in decline across most of the range.
These butterflies are non-migratory, and are generally found in close proximity to stands of the scrub oak or other prairie oak species.
It may be that population dynamics are closely tied to the ants species that tend caterpillars. However, more research is needed to identify what ant species are present and their effectiveness at protecting caterpillars.

Life Cycle

Adults

Edwards' hairstreak flies in July in New Hampshire. They produce one brood each year (univoltine) throughout the range.

Caterpillars

Caterpillars first eat buds. Then, as they grow larger, they will spend the day in ant nests protected from predators and consume leaves on the trees at night.

Caterpillars

Caterpillars spend the day in ant mounds at the base of young oaks (pictured here).

Eggs

Eggs are laid in the bark of young host trees. Eggs will hatch the following spring when trees bud.

Conservation

Listing Status

Edwards' hairstreak is listed as vulnerable in New Hampshire , and is a state listed there as a species of special concern. It is critically imperiled in Maine, Maryland, Oklahoma and Saskatchewan, Canada. It is imperiled in eight states. The butterfly is secure in only two states: Minnesota and Rhode Island.

Recovery Efforts

In New Hampshire the monitoring of Edwards' hairstreak populations is a first step to conserving the species.

Population Trends

We had one site for Edwards' hairstreak. We found no trend in abundance or phenology through this time. There is a large amount of variation in the timing and counts of butterflies, typical of insects.