Schinia lucens (Morrison, 1875)
Leadplant Flower Moth
Basis for Listing
The Leadplant Flower Moth (Schinia lucens) occupies an extensive range in mid-continental North America from southern Manitoba to Texas, east to Michigan and Illinois (Moth Photographers Group 2012; Metzler et al. 2005), roughly coincident with the range of leadplant (Amorpha canescens) (Kartesz 2015), its primary larval host plant. It also occurs in several southeastern and southwestern states (Moth Photographers Group 2012). In these states the Leadplant Flower Moth must utilize other Amorpha species as hostplant as they are beyond the range of leadplant. In the core of the moth’s range, including Minnesota, leadplant appears to be the only hostplant, and the moth is not known to occur in Minnesota where leadplant is absent.
Leadplant is a common component of upland prairie and savanna plant communities and was abundant in the prairie landscape of the state prior to Euro-American settlement. Today, this plant rarely occurs in Minnesota outside of native prairie and savanna remnants, which collectively comprise less than one percent of the original extent of these habitats in the state (Minnesota’s Remaining Native Prairie). Consequently, the total population of the Leadplant Flower Moth in Minnesota has been reduced to a tiny fraction of what it must have been a century or so ago. There are sporadic records of the species from several decades prior to the initiation of targeted documentation in 2005. Since then, surveys, principally by the Minnesota Department of Natural Resources (MN DNR) Parks and Trails in several state parks and by the Minnesota Biological Survey in many prairie sites, have added a number of new locations. Documented occurrences now span the southern third of the state and in the west extend north to Kittson County. These results suggest that this moth occurs in most upland prairie and savanna remnants in the state that support good leadplant populations, including strips flanking roads and railroads.
The Leadplant Flower Moth is apparently not a rare species in Minnesota, but its population is segmented by extreme habitat fragmentation into small colonies scattered in an inhospitable landscape. Continuing loss of its prairie habitat through overgrazing, conversion to cropland, and built development is a threat, but a more significant threat is the vulnerability of its small highly localized populations to extirpation caused by extreme weather events (drought, flood, hail), pesticide exposure (both insecticide and herbicide), and ill-timed fire (wild fire and prescribed). The dependence on flowering and fruiting of its hostplant amplifies the risks. Dispersal in this species has not been investigated, but the absence of detections of this moth outside of prairie habitats suggests that it rarely ventures away from them. If this is the case, failing colonies will not be rescued by immigration nor will failed ones be replaced. Without explicit efforts directed to its conservation, it is likely that the Leadplant Flower Moth population in Minnesota will continue to shrink, hence, its designation as a special concern species in 2013.
The Leadplant Flower Moth is a medium-small moth, with a forewing length (base to apex) of about 12 mm (0.5 in). In the resting position, with wings folded roof-like over its body, the moth measures about 17 mm (0.7 in.) from head to wingtips and about 10 mm (0.4 in.) wide. Males and females are nearly identical in size and coloration. The predominant color of the forewings is a wine red, which, in freshly emerged moths, is given a pinkish cast by white over-scaling. Several narrow, sharply zig-zag bluish-white lines cross from the leading edge to the trailing edge of the wings, and white scaling along the wing veins creates faint, very fine lines perpendicular to the more prominent transverse lines. The thorax is covered with a dense “fur” of long hair-like scales, whose coloring matches that of the forewings. The hind wings, which are exposed only in flight, have broad brownish-black margins and a straw yellow central area surrounding a triangular dark patch. The antennae in both sexes are threadlike. The mature larva is typically dark greenish brown and tan in alternating rings, overlain with a series of closely spaced thin, slightly wavy longitudinal white stripes. The head is uniformly glistening orange-brown. Younger larvae are generally a lighter green overall. The only moth in Minnesota that bears any significant similarity to this species is the closely related Bleeding Flower Moth (Schinia sanguinea), which is apparently quite rare in the state. The forewing pattern of the Bleeding Flower Moth is blotchier than the intricate mosaic pattern in the Leadplant Flower Moth, and the hind wings are uniformly dark. Its larval hosts are blazing star species (Liatris spp.), which bloom in late July and August, and the adult flight period of this moth occurs concurrently with this flowering period.
The Leadplant Flower Moth occurs in mesic to dry native prairie and savanna communities where leadplant occurs. Leadplant is a long-lived low shrub or semi-shrub that is characteristic of these communities and rarely occurs outside of them, except where adjacent prairie has provided a seed source. Most records of the moth in Minnesota are from native upland prairie habitat within the Prairie Parkland and Tallgrass Aspen Parklands provinces, but it is also known to occur in prairie and savanna habitats in the Eastern Broadleaf Forest Province.
Biology / Life History
The Leadplant Flower Moth has one generation a year, with adults flying during the flowering period of leadplant, which, in Minnesota, is from late June through mid-July most years. Like other species in the genus Schinia, collectively known as “flower moths”, Leadplant Flower Moths lay their eggs in the inflorescences of their host plant, and the larvae feed on the flowers and developing fruits (Hardwick 1996). In the case of leadplant, a legume, the latter are miniature pods crowded tightly together on the spike, each containing a single bean-like seed. The tiny hatchlings feed on flower parts and the tender newly forming fruits; by the time the fruits have matured and become tough, the larger older larvae have no difficulty consuming them. Larval development is completed in late July and August, at which point the caterpillar leaves the plant and burrows into the soil, where it forms a silk-lined chamber for pupation. The pupa overwinters in this underground cocoon, and the adult moth emerges the following summer as the leadplant begins to blossom. In some Schinia species, a fraction of pupae do not emerge the year following their development but pass the summer and another winter before emerging, evidently a form of insurance against the entire population emerging into unsuitable conditions (Hardwick 1996). Whether the Leadplant Flower Moth does this has not been investigated.
Leadplant Flower Moths are nocturnal (active only during darkness). During the day, the moths rest motionless amid the flowering/fruiting spikes of leadplant, where their coloration and pattern effectively conceals them. At rest, they hold their forewings folded over their body like a tent, covering their conspicuously marked hind wings. The resting moth most closely resembles the part of the flower spikes where the flowers have begun to wilt after pollination and are paler and more reddish than the deep blue-purple of freshly blooming flowers. During daylight, these moths will fly rapidly away when disturbed. It is hypothesized that the yellow hind wings provide a readily visible target for a pursuing predator, which is left befuddled by its sudden disappearance when the moth alights. To complete the adaptive relationship with leadplant, the coloring and patterning of the caterpillars conceals them on the fruiting spikes as they feed.
Adults feed on floral nectar and thus are likely to be pollinators. Collected specimens often have milkweed (Asclepias spp.) pollinia (pollen packets) attached to one or more tarsi (their “feet”), indicating that milkweeds are visited for nectar. In Wisconsin it has been observed nectaring on leadplant after midnight (Kyle Johnson, pers. com.). Nothing else appears to have been reported concerning their floral selection.
Conservation / Management
Protection of habitat where leadplant is common is fundamental to the future of the Leadplant Flower Moth in Minnesota. Because this plant is extremely slow to spread beyond the native prairie, savanna, and barrens habitats that it occupied prior to Euro-American settlement, conservation of remaining occurrences of these native plant communities is the highest priority. Prairie reconstructions that include leadplant will probably prove suitable for the moth; good numbers were observed in one such planting that included leadplant (Jim Sogaard, pers. com.).
The native habitats that support the Leadplant Flower Moth are subject to encroachment by shrubs and trees, ultimately converting them to woodland or forest, where leadplant can no longer survive. Management intervention to accomplish what drought, fire, and large animal grazing formerly did is a necessary component of the conservation of this moth. Prescribed burning has been the primary tool used in prairie management, which undoubtedly causes high mortality among the insects and other arthropods living in the prairie. The Leadplant Flower Moth, like most other Schinia species, pupates below ground (Hardwick 1996), and this affords it some protection from burns conducted while it is in the pupal stage. The amount of protection depends upon how deep the pupa is buried, and this is unknown. Late spring burns can result in delayed flowering of leadplant but not in the emergence of adult moths, depriving the adults of suitable inflorescences for reproduction. On the other hand, leadplant vigor generally declines as years pass without removal of the old stems, and this can result in years with very little flowering, again depriving the moth of its required resources for reproduction. Division of habitats into multiple management units, with burns scheduled in a rotation that assures adequate and timely leadplant flowering every year, is a practicable solution for larger sites. Smaller sites may require the use of haying to supplement very limited burning. Prescribed grazing may also be a useful management tool, but this has not been investigated.
Several programs and resources are available to land managers and landowners to help protect and manage remaining prairie parcels including the Native Prairie Bank program, the Native Prairie Tax Exemption program, and a prairie restoration handbook.
Research into the dispersal behavior of the Leadplant Flower Moth is needed to assess how serious a threat habitat fragmentation is to the persistence of the species. Additional survey work is needed to determine its full range and population status in Minnesota.
Conservation Efforts in Minnesota
The Leadplant Flower Moth has only recently been recognized as a species of conservation concern in the state. However, the longstanding efforts to protect remaining native prairie and related habitats by the MN DNR and other public agencies as well as by private conservation organizations, notably The Nature Conservancy, have been of enormous benefit to the moth. Growing recognition of the need to give greater consideration to the effects of prairie management on insects and other arthropods will strengthen the value of habitat protection. Official designation of the Leadplant Flower Moth as a species of special concern will increase the amount of attention it receives, resulting in greater knowledge of its distribution and abundance in the state. In 2005, the MN DNR began recording field observations of the moth and entering occurrence data into the Natural Heritage Information System.
Robert P. Dana, Ph.D. (MNDNR), 2018
(Note: all content ©MNDNR)