Northern metalmark
ExploreCalephelis borealis
Type: invertebrate
Status:
Species Guide
Northern metalmark
Calephelis borealis
Species Type: invertebrate
Conservation Status:
IDENTIFICATION
The northern metalmark is a small butterfly with a wingspan of just 1-1¼ inches. It is the only member of the Riodinidae family found in New Jersey; most are tropical species. The dorsal (upper) side of the wings is chestnut brown-patterned with a darker median band, two thin metallic silver bands near the outer margin with a band of dark spots between them, and a whitish outer fringe. The ventral (under) side of the wings is orange with alternating black and metallic silver markings. In flight, the flashes of orange may confuse or deter predators. The male's forewings are rounded, while the female's are squared. Unusual among butterflies, metalmarks often rest with their wings outstretched rather than pulled back together. They often perch on the undersides of leaves or on flowers in the sun.
This butterfly is quite unique and easy to identify. The most similar species in our region is the pearl crescent – a widespread orange and black patterned butterfly of generic open habitats whose flight period extends from April through November.
Northern metalmark caterpillars are green with black dots and long white hairs. They are well-camouflaged against the leaves of their host plant, roundleaf ragwort (Packera "Senecio" obovata). Ragwort plants often grow in dense patches, making it unlikely to find the butterfly larvae that live on or beneath them. Caterpillars of other species will feed on roundleaf ragwort, too, so insect damage alone cannot confirm that metalmarks are present. An experienced lepidopterist can distinguish metalmark larvae from others, but generally the adult (butterfly) is used for identification during its short summertime flight period.
Distribution & Habitat
DISTRIBUTION AND HABITAT
Northern metalmarks inhabit open limestone or shale outcrops, cliffs, and ledges where rocky soils limit forest cover. The larval host plant, roundleaf ragwort (Packera "Senecio" obovata), often forms a dense ground cover in these settings. Cedar glades often arise from such barrens and naturally favor the 60% canopy coverage preferred by metalmarks. Nearby meadows and streams are also used as sources of wildflower nectar and water. Forest gaps maintained by powerline rights-of-way, abandoned railways, and other disturbed areas are sometimes suitable for metalmarks.
The northern metalmark is known from only a few dozen remaining locations, though its distribution is relatively broad. It ranges from western Connecticut through Pennsylvania to the central Appalachians and the Ohio River Valley. Virginia and Kentucky are its southernmost Appalachian limits. Isolated populations exist in Arkansas, southwestern Missouri, and eastern Oklahoma. Within this overall range, strongholds occur from Connecticut to northwestern New Jersey (Sussex and Warren Counties), Pennsylvania to West Virginia, in Ohio, and in the Ozarks. Populations are small even in these locations, with surveys often tallying ten or fewer adults each.
Northern metalmarks follow metapopulation dynamics, whereby multiple small populations are scattered across a local landscape but are connected by natural corridors. These small populations are fairly insular, but in a healthy metapopulation they mingle and explore enough to swap genes and colonize new areas.
Diet
DIET
Northern metalmark caterpillars eat the leaves of roundleaf ragwort (Packera "Senecio" obovata). Golden ragwort (P. aureus) and Philadelphia fleabane (Erigeron philadelphicus) may also be used.
The adults take nectar from a variety of summer-blooming flowers, including butterfly milkweed, white sweet clover, goldenrods, black-eyed Susan, ox-eye sunflower, sneezeweed, fleabane, and yarrow.
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<h3 class="mb-0">Life Cycle</h3>
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<div class="mt-2"><h4>LIFE CYCLE</h4>
<p>Adult northern metalmarks have a short flight period lasting about 20 days between mid-June and late July. In most areas this is the only annual brood (though a second may occur in mid-August in the Ozarks). Adults often.jpg’est upside-down on the undersides of leaves, including shrubs and trees. They are slow, weak fliers, so they usually stay very close to their emergence site; thus it is critical to have enough nectar sources nearby. If scarce, the butterflies may travel short distances – such as to wetlands – in search of food.</p>
<p>The butterflies can usually be found on flowers in forest openings and along edges. They are most active at mid-day when the weather is warm and sunny, or in the morning or evening when days are hot. Males perch on leaves to scope out females.</p>
<p>After mating, eggs are deposited singly on the undersides of host plant leaves. The caterpillars hatch and feed on the leaves, going through five or six instars (growth periods between molts) before moving down to the ground for winter. The half-grown caterpillars hibernate in duff or soil beneath the basal leaves of their host plants. They emerge the following April and go through 2-4 final instars (of 8 or 9 total) before metamorphosis.</p>
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Scientific Classification
- Kingdom: Animalia
- Phylum: Arthropoda
- Class: Insecta
- Order: Lepidoptera
- Family: Riodinidae
- Genus: Calephelis
- Species: C. borealis