Northern metalmark

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.

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.

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 rest 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.

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.

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.

The northern metalmark is rare and localized throughout its range. Because populations are small, relatively isolated, and nestled within habitats that are also small, no population should be thought secure. The northern metalmark is currently listed as endangered in Connecticut only and as Threatened in Maryland. New Jersey considers the metalmark to be of Special Concern.

The main threats to this species are habitat loss to development, forest succession (canopy closure), invasive plant competition, and the fragmenting of metapopulations, which leaves smaller populations isolated. These effects may have already taken their toll on the species.

Deer overpopulation is another threat, since deer eat ragwort flowers as well as many others, reducing critical nectar sources and possibly the host plant. This problem may be especially pronounced in NJ. Gypsy moth spraying is believed to have had a negative impact on metalmark populations in New England, Maryland, and West Virginia. Spraying takes place at the time when caterpillars are emerging again in April. Ill-timed fire and other forest management activities can impact populations too.

Management to benefit northern metalmarks can include strategic land conservation, tree thinning in habitats where the canopy is too dense, invasive plant control, re-planting of native wildflowers, deer control or exclusion, and avoiding gypsy moth spraying over suitable metalmark habitats. Utility rights-of-way that may contain metalmark populations should be maintained in a way that promotes nectar sources while avoiding mowing and pesticide use when the caterpillars or butterflies could be present. Cleared rights-of-way could serve as expansion corridors if host plants are present (or planted). Even certain wind energy and natural gas developments could have promise for metalmarks as long as vegetation is managed appropriately. Of course, without proper management these developments could easily devastate populations.

In 2015, the New Jersey Endangered and Nongame Advisory Committee recommended changing this species' status from Special Concern to Endangered within the state, but no formal rule proposal has been filed to date.