Wild lupine
is a perennial plant in the pea family with beautiful pink to blue flowers.
It is found primarily on dry, sandy soils in open to partially shaded
habitats. Many of the areas where the lupine grows are oak savanna and
pine barrens plant communities. In addition to the Karner blue, these
communities support a diverse array of other rare plant and animal species
such as the Blanding's turtle and prairie fame flower. If the natural
forces (e.g., wildfires) that create or maintain these open habitats
are suppressed, management is needed. Lupines can occur in power line
rights-of-ways and utility corridors, military installations, forest
trails, and other open areas that are maintained as early successional
landscapes. Without natural or artificial disturbance, savanna and barrens
communities yield to shrubs or forests. Lupines in shaded habitats may
survive, but usually with poor vigor and without flowering. Eventually,
the lupines are shaded out, making the site unsuitable for Karner blues.
The Karner
blue butterfly's annual life cycle is inextricably tied to that of the
lupine. About mid-April, wild lupines sprout from rhizomes and forms
clumps of flowering stalks. Two generations of Karner blue butterflies
are produced each year. The first brood begins around mid-April, when
eggs laid the previous summer hatch. Tiny larvae crawl up the lupine
stems to feed on the new leaves. They eat the interior portion of the
leaf, leaving behind the surface layer and creating a "window pane"
effect. Dense stands of lupine are necessary to ensure that enough butterflies
are produced to maintain the population over time. Peak bloom is reached
by mid- to late May, when flowering lupines may create a sea of blue
in the open meadows of oak savannas and pine barrens. About the time
of peak bloom, the year's first brood of Karner blue larvae pupate.
Adults are usually flying from late May through early June.
During
the flowering period, the first-flight adult butterflies lay eggs on
or near the lupine plants. In about a week, they hatch. The season's
second brood of larvae feed through mid-July, when lupine flowering
is ending and seed pods are produced. The second-flight adults then
emerge through mid-August, depending on weather conditions. Because
they cannot depend on lupine flowers for food at that time, the adults
must have a variety of mid- to late summer flowering plant species to
serve as nectar sources. By the time second-flight females lay their
eggs, the lupine is dying back or is already dormant. The active periods
for both the plant and the butterfly last only about 4 months of the
year (Dirig 1994).
The ranges
of the wild lupine and Karner blue do not exactly overlap. Instead,
Karner blues are found along the northern extent of lupine's range.
Historically, the butterfly occurred in a rather narrow band extending
from eastern Minnesota, across portions of Wisconsin, Illinois, Indiana,
Michigan, Ohio, and Canada (Ontario), Pennsylvania, New York, and Massachusetts
to New Hampshire. Dirig (1994) surmises that Karner blues are limited
to areas where continuous winter snow pack is present for over 80 days.
Because the eggs are often deposited on bare sandy soil, where there
is little or no or vegetative litter to protect them, snow is necessary
to insulate the eggs from cold temperatures and the drying effects of
the sun.
Wild lupine
is a plant that thrives in areas that are periodically disturbed, which
reduces or eliminates overhead canopies and plant competition. Historically,
fire provided open barrens and savanna habitats for colonization by
lupine and Karner blues. Not surprisingly, fire suppression has consistently
been identified as the primary factor affecting the butterfly's population
decline and reduction in range. It is now extirpated from Ohio, Pennsylvania,
Massachusetts, Ontario, and probably Illinois, and is barely hanging
on in New Hampshire and Minnesota.
In the
eastern part of its range (New York and New Hampshire), the wild lupine
is most frequently found in remnants of habitat that have been artificially
disturbed, such as highway corridors, sand roads, utility rights-of-way,
abandoned sand pits, and airports. The Karner blue fares better today
in Wisconsin and Michigan than anywhere else. Landscapes supporting
lupines and butterflies in these States vary from public lands managed
as savannas or barrens to rights-of-way and military lands. Wildfire,
prescribed burns, and artificial disturbance--such as mowing and grazing--have
maintained a patchwork of open-canopied and lupine-dominated sites that
continue to support Karner blue butterflies.
The future
for the Karner blue lies in active management to simulate the historic
role of fire in maintaining oak savanna and pine barren habitats. The
Fish and Wildlife Service looks forward to working with its many partners
in the protection of this endangered butterfly, the wild lupine, and
the ecosystems upon which both depend.
Dirig,
R. 1994. Historical notes on wild lupine and the Karner blue butterfly
at the Albany Pine
Bush, New York. Pages 23 -36 In KARNER BLUE BUTTERFLY: a symbol of a
vanishing landscape. Edited by D.A. Andou, R. J. Baker, and C.P. Lane.
St. Paul, MN Ag.
Exp. Stn.
________________________________________________
Kim Mitchell and Cathy Carnes are wildlife biologists in the FWS Twin
Cities, Minnesota,
Regional Office and Green Bay, Wisconsin, Field Office, respectively.
November 1996
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