New Jersey Butterfly Club

White M Hairstreak

Parrhasius m-album

Identification: Very small—but our largest hairstreak (just a bit larger than Coral). Almost never seen with wings open. Above: FW and HW bright, iridescent blue that can be seen when the butterfly flies or rubs its wings back and forth. Below: Gray to brown with distinct white line bordered with black across each wing. Line forms an obvious "M" near tails. Large red-orange spot on HW is set inward away from margin, touching the “M” mark, and neighboring blue spot lacks an orange cap. A single white dot (or dash) near leading edge of HW is distinctive. Similar hairstreaks: Oak Hairstreak is dark above, usually lacks the isolated white mark near the leading edge of the HW below, and orange spot near HW tails does not touch the “M”. Gray Hairstreak is pearl-gray below (but may appear brown when heavily worn), the postmedian bands include orange (and usually do not form as conspicuous an "M"), also lacks the white HW mark, and the orange spot at HW tails is distinctly squarish with a more-conspicuous black spot outwardly.

NJ Status and Distribution: Resident. Generally uncommon to rare in the northern counties but fairly common in South Jersey. Almost always seen as single individuals.

Habitat: Open areas with flowers near woods with oaks. Frequently seen in gardens.

Flight Period: Late April to mid-October. Extreme dates: North Jersey 4/13—11/5; South Jersey 3/16—11/18.

Caterpillar Food Plants: Oaks (Quercus).

Overwintering Stage: Pupa.

Good Locations: Higbee Beach WMA, Belleplain SF, Dennis Creek WMA, Glassboro WMA; in North Jersey its occurrence is so erratic that no reliable location can be specified.

Comments: Likes to nectar on milkweeds, Indianhemp, sedums, and Chinese Lespedeza (Lespedeza cuneata)—the last an alien, highly invasive species. Always a good find. Watch for that flash of blue when it flies!