New York Natural Heritage Program
White-m Hairstreak
Parrhasius m-album (Boisduval and Le Conte, [1833]) (1793)
Insects

Identifying Characteristics [-]
The adult is about 1.5". Its tailed upper wings are iridescent blue with black borders. The underside is grayish brown, with a white postmedian line edged with black and forming a white "M" near the tails and a white costal spot. Caterpillars are yellow-green and hairy.

Characters Most Useful for Identification [-]
The dorsal iridescent blue and ventral gray with a costal white dot and white "M" in the postmedian line on the hindwings is diagnostic (Opler and Krizek 1984).

Best Life Stage for Proper Identification [-]
Adult.

Behavior [-]
Adults obtain nectar from flowering trees, and thus this species mostly dwells in the canopy and only occasionally comes down to the forest floor to feed. Males perch watching for females; flight is fast and direct and they can drop straight down from the canopy to land on a flower to feed. Overwinters as a pupa in litter beneath host plant (Cech and Tudor 2005; Sourakov 2008).

Diet [-]
Caterpillar hosts include various species of oaks (Quercus). Adult food sources include a variety of nectar sources such as sumac, viburnum, sourwood, wild plum, dogwood, goldenrod, and common milkweed (Opler and Krizek 1984). Adults have been observed at goldenrod, white clover, and Eupatorium perfoliatum in New York.
White-m Hairstreak Images
click to enlarge
The Best Time to See
This species has two broods in the northern parts of its range (Opler and Krizek 1984) and Glassberg (1993) provided data from the 1980s on two flight periods in the New York City area: the end of April to the end of May, and early July to early September. Records from 2002-2005 (Fiore and Wallstrom 2003-2006) also showed two distinct flight periods (broods) in southern New York, from early April to late June, and from late August to early October, suggesting that this species has recently lengthened its flight season.
J F M A M J J A S O N D
Present Active
The time of year you would expect to find White-m Hairstreak present (blue shading) and active (orange shading) in New York.
Similar Species
  • Gray Hairstreak (Strymon melinus)
    The White M Hairstreak has an additional white mark on the leading edge of the ventral side of the hindwing, and a more noticeable "M" on the outer ventral hindwing.
  • Oak Hairstreak (Fixsenia favonius)
    The inwardly displaced orange and black spot on the hindwing distinguishes the White M from the Oak Hairstreak