New York Natural Heritage Program
Hessel's Hairstreak
Callophrys hesseli (Rawson and Ziegler, 1950)

Identifying Characteristics [-]
This is a small butterfly (1") with emerald green tailed wings; the upperside is dark brown with few obvious markings, while the underside has a reddish-brown ground color overlaid with with bright bluish green and white spots and lines. The 1/2" larva is deep blusih green with a series of subdorsal lustrous white boomerang-shaped bars on each segment, rendering it cryptic on the host plant (Rawson et al. 1951, MDIFW 2003, Cassie 2011).

Characters Most Useful for Identification [-]
Habitat is the most reliable factor to use, as Junipers are confined to dry Redcedar old fields and ridges, while the Hessel's occupies only Atlantic white cedar swamps.

Best Life Stage for Proper Identification [-]
Adult male.

Behavior [-]
Butterflies in this genus have been shown to change their tree perch positions in response to the position of the sun, often moving to the tops of the cedars at midday where they form leks, court, mate, and lay eggs (Johnson and Borgo 1976; Cryan 1985). The adults are often first noticed fluttering out from a tree that has been jarred and they remain primarilly within swamps but may travel up to 1/2 mile in search of nectaring plants (MDIFW 2003; Vaughn and Shepherd 2005; Cassie 2011). Adults suffer from bird predation and individuals in this genus only live for several days (Beck and Garnett 1983).

Diet [-]
In the wild, caterpillar larvae feed exclusively on new growth of the Atlantic White Cedar (Chamaecyparis thyoides). Adults nectar at flowering bog plants including Cranberry and Highbush Blueberry (Vaccinium spp.), Shadbushes (Amelanchier), Chokeberry (Aronia), and Buttonbush (Cephalanthus) (Cryan 1985).
Hessel's Hairstreak Images
click to enlarge
The Best Time to See
Hessel's Hairstreaks are easily overlooked due to low abundance, inaccessibility of the habitat, a short and unpredictable flight season, habit of perching high in the canopy, small size, and cryptic coloration and behaviors. Thus, very little is known of its life history in New York. Adults have been reported from May 23 only. In neighboring states the adult flight season is generally in May and early June (with a peak in late May), earlier into April southward into New Jersey and later in June northward in Maine. Northward from New Jersey a single spring brood is produced, while southward into North Carolina, a summer brood also emerges (MDIFW 2003, Massachusetts NHESP 2007, Vaughn and Shepherd 2005). However, there is some indication that this species may have historically been partially double brooded on Long Island (Cryan 1985). In Massachusetts, eggs are laid on cedar branch tips in late May and following a brief egg stage, larvae feed on new growth of the host plant for about a month, pupating in July. Pupae enter diapuse in July and emerge the following spring (Massachusetts NHESP 2007).
Reproducing Larvae present and active Eggs present outside adult Pupae or prepupae present
The time of year you would expect to find Hessel's Hairstreak reproducing (red shading), larvae present and active (blue shading), eggs present outside adult (green shading) and pupae or prepupae present (orange shading) in New York.
Similar Species
  • Juniper Hairstreak (Callophrys gryneus)
    Hessel's Hairstreak can be differentiated from its sibling species, the Juniper Hairstreak, by subtle details of the underwing pattern incluidng the outward offset of the first white spot on a band of spots on the underside of the forewing. Habitat is the easiest factor to use, as Junipers are confined to dry Redcedar old fields and ridges, while the Hessel's occupies only Atlantic white cedar swamps. There is strong evidence that this type of habitat segregation is the first step in host race formation, implying that these two species are in the very earliest stages of speciation (Nice and Shapiro 2001; Forsiter 2004; Downey and Nice 2011).