Swamp Metalmark Natural History

The metalmarks are small butterflies that occur principally in the tropics of the New World.  Many species are very attractive and show gorgeous colors.  In the United States, where only a few species dwell, they are for the most part dull or nondescript butterflies as regards the upper surfaces.  The undersides, however, are much more attractive and often display tiny metallic markings or lines. Adult males have more pointed forewings and reduced forelegs; while females have six well developed legs. 

In the eastern half of the country there are three native metalmarks but only the swamp metalmark (Calephelis mutica) occurs in Wisconsin.

The swamp metalmark is a rusty orange-brown which is cobwebbed with darker markings. Two parallel rows of metallic lead-colored dots follow its upper wing margins from which it gets its name.  The undersides are remarkably bright and uniform shade of golden orange, heavily speckled with tiny, variously shaped black markings. This tiny dime-sized butterfly has a wing span that is less than one inch.

Life Cycle

The swamp metalmark has one generation per year which begins when the female selects suitable places beneath the downy leaves of swamp thistle (Cirsium muticum) to lay her eggs.  The minute pale green eggs require from two to four weeks to hatch and the larvae (5-6 mm in length) feed a short time before hibernating. They over-winter on the ventral side, along the midrib near the base of the basal rosette of the swamp thistle. 

The following spring the caterpillar resumes activity and attains maturity by early July. At this time it is green and covered with long whitish hairs.  By late July or early August most adults have emerged from the pupal stage and may usually be found perched upon the low-growing grasses or slightly taller vegetation of the swamp lands. Their flight period ranges from late June to mid August.  Depending on the size of the population the flight period may last 2-3 weeks, although most individuals probably live for only a few days.  Dispersal flights tend to be short distances, weak and close to the ground.

Critical habitat features needed by the swamp metalmark butterflies include areas with open, low vegetation with an abundance of the larval food plant (swamp thistle) and suitable nectar plants.  Nectar plants include mountain mint, black-eyed susan, swamp milkweed, shrubby cinquefoil and yarrow. 

Range 

In Wisconsin the adults possibly occur in swampy locations throughout the southern part of the state where the food plant grows, but may be very easily overlooked because of their later flight period, small size, and strict choice of habitat.  As of November 2009 there are only two confirmed populations including one reintroduction at Riveredge Nature Center in Ozaukee County and one in the Northern Kettle Moraine State Forest in Fond du Lac County.

This species is reported as rare to endangered throughout its range, which includes Michigan, Ohio, Indiana, Kentucky (one record), Illinois, Arkansas and Missouri.

More to Come: 

What is Riveredge is Doing to Track the Swamp Metalmark?