New Jersey Butterflies

Edwards' Hairstreak

Satyrium edwardsii

Identification: Very small—size of thumbnail. Almost never seen with wings open. Below: FW and HW light grayish-brown, with postmedian markings consisting of clearly-defined, white-ringed, dark ovals rather than the white-edged, darkish bands of many other Satyrium hairstreaks, such as Banded. Several orange spots along HW margin, interrupted by a large blue spot with a tiny, hard-to-see orange cap. Similar hairstreaks: Acadian is grayer below and has a bold orange cap on the blue spot; although their flight periods overlap these 2 species occupy very different habitats.

NJ Status and Distribution: Resident. Uncommon, but can be locally common. Most common and widespread in Sussex and Warren counties, but also reported from Bergen and Passaic counties. Rarer and even more local in South Jersey.

NJ Range Map-Edwards' Hairstreak

Habitat: Woodland edges with shrubby oaks. Most often reported from utility line easements, and mountaintop ridges and balds.

Flight Period: One brood that flies from mid-June to early August. Extreme dates: North Jersey 6/15—8/2; South Jersey 6/15—7/24.

Larval Food Plants: Mainly Scrub Oak (Quercus ilicifolia) but possibly small shrubby oaks of other species in the Red Oak group.

Overwintering Stage: Egg.

Best Locations: Crater Lake Rd., Blue Mt., Sunrise Mt.

Comments: This species is dependent on ants—Formica integra, and possibly other species in this genus. The ants protect the larvae, “escorting” them from an ant-built shelter at or near the base of a host plant—up into the branches where the larvae feed on leaves at night, and then back to the shelter. What’s in this for the ants you ask? Apparently irresistibly sweet secretions from the larvae.

Edwards' Hairstreak

Crater Lake Rd., Sussex Co., NJ, 6/26/11.

Edwards' Hairstreak larva

Larva attended by ants.

Scrub Oak

Scrub Oak (Quercus ilicifolia), which is the main host plant for Edwards' Hairstreak.