Callophrys hesseli

Distinguished from other Callophrys hairstreaks by combination of: (1) olive green and rusty brown wing coloration with white marginal bands, (2) exclusive association with Atlantic white-cedar wetlands, (3) Atlantic coastal plain distribution. Similar Juniper Hairstreak (Callophrys gryneus) occurs on eastern red cedar in different habitats and lacks the rusty brown base color. Henry's Hairstreak (Callophrys henrici) uses different host plants (various hollies).

Strictly confined to terrestrial wetlands supporting Atlantic white-cedar: Atlantic white-cedar swamps, bogs, riparian wetlands, and forested wetlands. Requires mature cedar stands with sufficient canopy structure for adult perching and mating.

Atlantic coastal plain from southern Maine south to Florida Panhandle. Core population density in New Jersey. Estimated 21–300 populations total, with only 13–125 considered stable. Extirpated from New York (surveys in 1990s found none).

Adults active in May. Eggs laid in early May, hatch after 4–6 weeks. Larvae feed through growing season, enter pupal diapause during winter. Adult lifespan 1–2 weeks.

Larvae feed exclusively on foliage of Atlantic white-cedar (Chamaecyparis thyoides). Adults consume nectar from: swamp milkweed (Asclepias incarnata), shadbush (Amelanchier), sand myrtle (Kalmia buxifolia), sweet pepperbush (Clethra alnifolia), highbush blueberry (Vaccinium corymbosum), buttonbush (Cephalanthus occidentalis), and dogbane (Apocynum).

• Chamaecyparis thyoides - exclusive larval hostAtlantic white-cedar; complete life cycle dependence

Egg stage (4–6 weeks, early May). Larval stage (herbivorous, feeding on cedar foliage). Pupal stage (overwintering diapause). Adult stage (nectarivorous, 1–2 week lifespan). Eggs deposited on branch tips of Atlantic white-cedar to ensure immediate food availability for emerging larvae.

Adults perch on cedar tree tops, shifting position in response to sunlight levels. When disturbed, groups disperse in swirling flight. Males aggregate at tree tops to scout for females; females remain at lower levels until mating season. Males compete for female attention in lek-like aggregations at midday. Courtship, mating, and oviposition occur during midday period on cedar trees.

Specialized herbivore tightly coevolved with Atlantic white-cedar. Serves as indicator species for intact cedar swamp ecosystems. Larval feeding has minimal impact on host trees due to low population densities and lack of competition in specialized habitat.

Conservation concern due to habitat loss. Listed as endangered in Connecticut. Protected under MESA in Massachusetts. Subject to monitoring programs in New Jersey where sightings inform conservation planning. Named in honor of lepidopterist Sidney Adolphus Hessel.

• Callophrys gryneusJuniper Hairstreak; similar green coloration but uses Juniperus hosts, occurs in different habitats, lacks rusty brown wing base
• Callophrys henriciHenry's Hairstreak; uses Ilex hosts, different habitat and distribution

• butterfly
• lycaenid
• hairstreak
• wetland specialist
• endangered
• Atlantic white-cedar
• host-specific
• diapause
• lek mating

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• Bug Eric: Year-end Wrap-up
• Bug Eric: City Nature Challenge 2023 Recap