Rare Species Guide

  Basis for Listing

The phlox moth is considered to be rare throughout its limited range, which extends from Minnesota through Wisconsin, Illinois, Indiana, and Michigan, with apparently disjunct records from Arkansas and Texas. There are no recent records from Arkansas, Texas, or Illinois, and the species is considered imperiled to critically imperiled in the other three states east of Minnesota (NatureServe 2008). The phlox moth was first documented in Minnesota in 1976, and has been found at only four other locations since then. All occurrences are in native prairie remnants in the western part of the state. This moth is limited to prairies, savannas, and sandy open woodlands where its larval food plant grows. It is difficult to detect, and may be more common in the state than the few records indicate. However, less than 1% of Minnesota's original prairie remains, and this continues to diminish. Rapidly increasing development severely threatens the sandy woodland habitats. For these reasons, the phlox moth was listed as a special concern species in Minnesota in 1996.

  Description

In the phlox moth, the sexes are similar in size and coloration. Adults are small, with a forewing length (base to apex) of 8-10 mm (0.31-0.39 in.). The forewings are gray-violet with a patch of crimson near the base and a broad crimson band near the margin. There is a prominent fringe of pale tan to gray scales in fresh individuals. The thorax is clothed in a dark violet-gray fur of long hairlike scales. The hind wings, rarely visible in living moths, are a dark charcoal with a pale fringe. Adults are usually observed resting on the inflorescences of prairie phlox (Phlox pilosa var. fulgida), their wings folded back over their bodies like a tent, where their coloration makes them resemble a recently withered phlox blossom. There is no similar moth in Minnesota.

  Habitat

In Minnesota, the phlox moth has been observed only in native upland prairie habitat. In Wisconsin, most documented occurrences are in sandy savanna or barrens habitats (Wisconsin DNR 2008). The crucial habitat feature is the presence of prairie phlox, the larval food plant.

  Biology / Life History

As its name implies, the phlox moth is intimately associated with phlox. The only documented larval food plant in the wild is prairie phlox, although larvae have been successfully reared in captivity on other phlox species. Larvae eat the reproductive parts of phlox plants: early instars (developmental stages) bore into the flower bud and developing ovary, while later instars feed externally on the ripening fruit (seed capsules) (Hardwick 1996).

Adults emerge from pupation and are active at about the same time that prairie phlox is in bloom, from late May through much of June. Females lay their eggs singly, primarily in the phlox flowers on the inner face of sepals. Eggs hatch in 3-6 days, and larvae complete their growth in a little more than 2 weeks. When mature, larvae bore into the soil and pupate in a silk-lined cell (Hardwick 1996). The pupal stage lasts approximately 10 months, until the following May or June. In some species in the genus Schinia, a fraction of pupae do not emerge at the completion of the first annual cycle, but may pass 1 or more additional cycles before emerging; it is not known whether this happens in the phlox moth.

Little has been published about the behavior of adult phlox moths. They are apparently active in the daytime, not at night (Hardwick 1996), but the flight is very rapid, making observation difficult. Adults are rarely seen except when resting on phlox inflorescences; they are apparently less prone to flying off when approached if it is cloudy, making observation more likely under these conditions (Swengel and Swengel 1999). They take nectar from phlox and other flowers. As prairie phlox colonizes severely disturbed areas slowly and has limited dispersal capabilities, it seldom occurs in Minnesota outside of remnant native habitats, and therefore the phlox moth is likely to be highly restricted to these remnants as well. Population densities are unknown.

  Conservation / Management

Survey work is needed to determine if the phlox moth is more common in Minnesota than current records indicate. Prairie phlox is typically present in remnant native prairies as far north as Polk County. Survey work is also needed in sandy woodlands and barrens east of the prairie-forest boundary.

Because the phlox moth is underground as a pupa at the times when most prescribed burning for vegetation management is done, it may not suffer significant mortality during these burns. This depends, however, on how deep the pupa is buried, and this is not known. Whether or not pupae are killed, burns that occur late enough in spring to suppress the production of phlox flowers that year could extirpate the moth from a site, as could mowing or grazing that prevents flowering or that destroys the floral resource before significant numbers of the moth larvae have completed their development.

The small size and isolation of most remnants that may provide habitat for the phlox moth means that most colonies of the moth are likely to be small and thus highly susceptible to extirpation. Management of sites where this moth is known or is likely to occur should be carefully conducted so that practices that have the potential to harm the moth are limited to only a portion of the habitat during any population cycle, and so that recolonization of treated areas is assured before an additional area is treated.

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.

  Conservation Efforts in Minnesota

The five known occurrences of the phlox moth are within protected sites managed to maintain the native prairie. Three of these sites were recently discovered during the first survey effort directed at this species, which was limited to eight counties in the southwest corner of the state. This suggests that the moth is likely to occur at many other protected and managed prairie remnants in Minnesota. Guidelines for protecting Lepidoptera populations within a fire-management program are employed by most of the major owners of potential phlox moth habitat in Minnesota, and efforts have been made to educate other land managers. Data on the locations of phlox moth colonies are maintained by the Minnesota DNR's Natural Heritage and Nongame Research Program and consulted during the state environmental review process so that projects can be modified to reduce or avoid harm.

  References and Additional Information

Hardwick, D. F. 1996. A monograph to the North American Heliothentinae (Lepidoptera: Noctuidae). David F. Hardwick, Ottowa, Ontario. 281 pp.

NatureServe. 2008. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.0. NatureServe, Arlington, Virginia. . Accessed 9 June 2008.

Swengel, A. B., and S. R. Swengel. 1999. Observations on Schinia indiana and Schinia lucens in the midwestern United States (Lepidoptera: Noctuidae). Holarctic Lepidoptera 6(1):11-21.

Wisconsin Department of Natural Resources [WIDNR]. 2008. Phlox Flower Moth Schinia indiana (Smith). . Accessed 28 October 2008.