Pyrgus centaureae wyandot (Appalachian grizzled skipper [AGS]; fig. 1) is a small (22–33-millimeter wingspan), dark brown-black butterfly with two irregular bands of white spots on the forewing (Allen, 1997). The U.S. Fish and Wildlife Service (FWS) considers the AGS to be at-risk (a declining species that is not currently protected under but may need the protections of the Endangered Species Act of 1973 [16 U.S.C. §§ 1531-1540]; FWS, 2018). The FWS is performing a discretionary review to fill knowledge gaps about the current status of AGS populations and assess whether the species should be listed as threatened or endangered (FWS, 2024). To inform these efforts, surveys were done to determine the range-wide relative abundance of AGS. Our findings can provide Federal and State natural resource managers with information so that effective strategies to protect the AGS can be developed and implemented.

Precise survey site locations are not provided here because the information has limited availability owing to restrictions (that is, for the protection of the colony locations and the privacy of the landowners). A general overview of AGS habitat is given in the following sections.

The overall objective of this study was to complete range-wide surveys to locate extant AGS colonies and to quantify the number of AGS observed at each location.

Specific objectives included the following:

Surveys were done in eight of the nine states that comprise the historical range of AGS: Maryland, Michigan, New York, North Carolina, Ohio, Pennsylvania, Virginia, and West Virginia. No survey results were reported by the New Jersey Department of Environmental Protection, and the District of Columbia was not surveyed because the most recent AGS record was from 1868 (Parshall, 2002). Therefore, New Jersey and the District of Columbia are not included in this report’s “Results” section. Necessary permissions and permits were secured before entering private lands.

The specific methods used to achieve the study objectives are discussed in the following sections.

Historically, the core of the AGS’s range was the shale region from Huntingdon County, Pennsylvania, into western Maryland, western Virginia, and eastern West Virginia. A few isolated AGS colonies occurred in New York. Colonies or individual AGS have also been recorded in non-shale habitats in North Carolina, New York, southern Ohio, southeastern Pennsylvania, northwestern New Jersey, northern Virginia, and Washington, D.C. The AGS colonies of the Michigan population were found in various habitats, including exposed limestone bedrock communities that are structurally like Appalachian shale habitats (Schweitzer and others, 2011).

Historical AGS data show that they have occupied suitable habitats in at least 77 unique counties (sum of the red, blue, and green counties in figures 6–13). Of the 77 counties, the 25 unique counties (green counties in figures 6–13) surveyed in this study were selected based on the most reliable information on known colonies and habitat characteristics of remotely selected sites. Of note is that despite the distant last reported observation dates (tables 11–18), in many of the 77 counties, periodic surveys and observations by entomologists and butterfly enthusiasts have continued over the years. For example, the last known AGS observation in Pennsylvania happened in Huntingdon County in 2012. However, the Western Pennsylvania Conservancy and its volunteers and partners have visited the site more than 47 times between 2014 and 2019. These surveys did not locate AGS.

In this study, AGS were observed in only 2 (2.6 percent) of the 77 known historical counties (a 97.4 percent decline in the number of counties where AGS were found). The long-term, range-wide population trend for AGS has declined by 80–90 percent, and the AGS conservation status ranks for the nine states include “Possibly Extirpated” and “Critically Imperiled” (NatureServe Explorer, 2025). The precipitous decline in the number of AGS populations is a concern for the survival of the species.

The AGS is a monophagous species. The larvae feed exclusively on Dwarf Cinquefoil or Wild Strawberry (Allen, 1997). Although these plants are commonly found in a variety of habitats (for example, barrens, fields, alvars, lawns, forest clearings), most habitat patches with the host plants remain unoccupied by AGS. A habitat patch must contain larval host and adult nectaring plants to harbor an AGS colony, but the presence of these plants does not guarantee that the patch will attract or hold an established AGS colony. There are at least three possible reasons as to why suitable habitat patches remain unoccupied by AGS:

The steep range-wide historical extirpation of AGS appears to have been driven by the interaction between various stressors and the life history of the species. These stressors also continue to interfere with establishment of new AGS colonies. The AGS’s vulnerability to various stressors arises from the direct and indirect intersections of the stressors with AGS’s life history (behavior, phenology, physiology, and dependence on metapopulation networks). In areas that are occupied by AGS, the stressors that adversely affect the abundance and distribution of the host and nectaring plants can indirectly translate to negative effects on AGS populations. The AGS are also vulnerable to the direct adverse effects of stressors. Some interactions between the life history traits and stressors that may be indirectly or directly contributing to the decline in populations of AGS include:

Over the decades, as the threats have increased, the number of colonies that have been extirpated from their metapopulations has increased, and the remaining active colonies in those clusters have become increasingly isolated, with consequent ramifications for the longevity of these colonies. Throughout their range, the metapopulation networks of AGS have been deconstructed mainly by ecological succession, widespread insecticide applications, and other human activities. For example, statewide AGS extirpations have occurred in New Jersey (New Jersey Department of Fish and Wildlife, 2015) and New York, and regional AGS extirpation has occurred in southeastern Pennsylvania (NYSDEC, 2014, 2015; Betsy Leppo, Western Pennsylvania Conservancy, oral commun., 2025). In a healthy metapopulation, some of the colonies may be extirpated by stressors, but the metapopulation can continue to survive as long as dispersal and colonization among the remaining colonies continue (Saccheri and others, 1998). If, however, enough colonies in a metapopulation become extirpated, the protections afforded to the surviving colonies by their metapopulation structure can be lost. Therefore, it is reasonable to assume that in declining metapopulations, although anthropogenic and natural stressors may be responsible for the initial losses of colonies in metapopulations, the subsequent losses of the surviving colonies may result from isolation. This in turn may further erode the remnant metapopulations and may eventually result in species extinction (Hill and others, 1996; Thomas, 2000; Higgins and Lynch, 2001).

In the following sections, two examples will illustrate the erosion of a metapopulation and colony resilience. Please note that the explanations provided on AGS metapopulation extirpations in southern Ohio and the resilience of AGS colonies in Virginia and West Virginia are based on assumptions drawn from survey data, metapopulation theory (Hill and others, 1996; Gutiérrez and others, 1999), and AGS life history.

Example 1.—Erosion of a metapopulation (figure 14).—The AGS colonies have been recorded in six locations in southern Ohio. The stressors responsible for colony extirpations are known for only two of the six colonies. Insecticides are not attributed to the extirpation of any of the southern Ohio colonies because, at the time of extirpation, spongy moth had not spread to this region (Shuey and others, 1987).

Parshall (2002) discussed the history of AGS in southern Ohio. In 1971, an AGS colony was found in southern Ohio’s Vinton County. This colony remained active until 1983. Repeated surveys to find AGS in Ohio over the next 20 years did not produce any additional sightings. Another colony was reported in the early 1980s in neighboring Athens County, but little is known about it. In 1986, a large colony was located in Hocking County, but it was destroyed in the early 1990s when its habitat patch was replaced by a parking lot. A second colony in Athens County was found in 1988, and it lasted until 1989. A single AGS was seen in Morgan County around 1988, but no further information is available about this colony. A second colony in Hocking County was discovered in 1993. This colony was eliminated by 1996 because of the loss of AGS host and nectaring plants from ecological succession. Lastly, a third Hocking County colony was found in 1999 but was lost by the early 2000s (fig. 14; app. 12; Parshall, 2002). Parshall (2002) noted that at this site, there was an abundance of host plants, yet AGS have not been observed there since the early 2000s. This was the last known sighting of AGS in Ohio (app. 12).

Possible explanations for why no new AGS colonies have been located since the early 2000s may be that fewer surveys are being done now than before 2000, or the AGS metapopulation in southern Ohio may have finally become dysfunctional in the early 2000s because too many of its colonies were extirpated. That is, the eroded metapopulation network could no longer sustain its remnant isolated colonies.

A healthy metapopulation network maintains its resilience to intrinsic (for example, inbreeding because of isolation) and extrinsic (for example, mortalities from insecticide applications) stressors. Fox and others (2017) have suggested that a metapopulation would become extinct when all its colonies are simultaneously extirpated. Almost simultaneous collapse of all AGS colonies in a metapopulation is a reasonable scenario after range-wide, large-scale forest insecticide applications. The insecticides would have initially reduced the number of active colonies and any surviving colonies would have subsequently gone extinct due to isolation. These two phenomena (insecticide applications and the subsequent destruction of the surviving colonies because of isolation) may explain the AGS extirpations that followed the progression of the U.S. Department of Agriculture’s spongy moth control program’s application path in the Eastern United States (Parshall, 2002).

Example 2.—Colony resilience.—In our study, AGS were observed in only two counties in two states: Alleghany County, Virginia, and Greenbrier County, West Virginia. Before the use of insecticides for spongy moths, AGS were documented in 21 Virginia counties and were considered a common “generally distributed” skipper in “all suitable localities” in the mountains of Virginia (refer to Schweitzer and others, 2011). Widespread insecticide applications for spongy moths in Virginia began in the 1980s, and by 1992, AGS were documented in only four counties. A 10-year survey (1992–2002) by the Virginia Department of Conservation and Recreation, Division of Natural Heritage, reported AGS in only two counties, Alleghany and Rockbridge Counties (Chazal and others, 2004). In 2000, several small AGS colonies were discovered in Alleghany County, Virginia. Our survey (2021–24) of eight Virginia counties (including Rockbridge County) found AGS colonies only in Alleghany County (fig. 12).

West Virginia had a similar situation to Virginia. Before the widespread, heavy use of insecticides for spongy moths had started in the late 1980s (Parshall, 2002; NatureServe Explorer, 2025), AGS were not considered to be “rare” in West Virginia (Parshall, 2002) and were documented from five West Virginia counties (fig. 13). The colonies in these counties are believed to have been extirpated by insecticides (Allen, 1997; Schweitzer and others, 2011). However, in 2009, a colony (the core colony) was discovered in Greenbrier County, West Virginia (FS, 2009a). The Greenbrier County colony was active during our survey (2021–24; fig. 13).

Although the other known AGS colonies and their metapopulations in Virginia and West Virginia are considered to have been extirpated (Susan Olcott, West Virginia Division of Natural Resources, oral commun., 2021; Chazal and others, 2004), the colonies in Alleghany County have been active for at least 24 years and the core colony in Greenbrier County has been active for at least 15 years. We suggest that the resilience of these colonies may be attributed to three factors.

First, Alleghany County, Virginia and Greenbrier County, West Virginia are juxtaposed (fig. 15). The linear distances between the colonies in these counties range from only 9 to 15 km (Steven Roble, Virginia Natural Heritage Program, written commun., 2017). The persistence of these colonies may stem from their proximity to each other (clustering of colonies). That is, the colonies may be close enough to maintain their genetic diversity through dispersal and interbreeding (that is, sustaining the metapopulation dynamics). Genetic testing could elucidate the relationships among these extant colonies.

Second, the Appalachian County and Greenbrier County colonies, in addition to being in two different states, may have survived because they may have experienced different habitat management practices. For example, the known extant colonies in Alleghany County are on private lands and in the FS’s George Washington and Jefferson National Forests, and the known extant colonies in Greenbrier County are nestled in the FS’s Monongahela National Forest (FS, 2009a). Therefore, the metapopulation network composed of the Alleghany County and Greenbrier County colonies may have survived extirpation because the colonies may not have received simultaneous insecticide applications or even the same insecticide products. The possible asynchrony in application timing and the possible differences in pesticide active ingredients and formulations may be providing the Virginia and West Virginia colonies windows for dispersal to maintain genetic diversity

Third, it is possible that these colonies have not been challenged with the threats (for example, insecticides) that have extirpated the other colonies.

To our knowledge, these colonies form the only known extant, functioning metapopulation network for AGS. To sustain this network over the years, safe corridors for genetic exchange among the colonies are needed (Jangjoo and others, 2016). The inter-patch dispersal distances of genus Pyrgus are not well studied and may depend on a specific species in the genus and their habitat (average distance less than 300 m [Widhalm and others, 2020], but flight distance for some species may exceed 1.5 km [Brereton and others, 1998]). Because the distances between the Greenbrier County and Alleghany County colonies are greater than the average dispersal flight distance, there may be suitable habitat patches and additional colonies along the dispersal route that maintain the connections between colonies across state lines. Additional searches in the vicinity of these colonies could provide knowledge of undocumented colonies and suitable habitat locations.

Uncertainties associated with AGS counts include the following:

Without intervention, the AGS may be at high risk of extinction because (Schweitzer and others, 2011; Wilson and Primack, 2019):

The results of this study provide the FWS and state fish and wildlife agencies with an updated range-wide status assessment for AGS, demonstrating that the distribution has contracted, with extant populations in only a small percentage of its historical range. These surveys also demonstrated that unoccupied, suitable sites exist in several states, suggesting that habitat degradation was not solely responsible for these declines. Future efforts to stabilize and strengthen the remaining populations could ensure suitable habitat remains available and is distributed in ways to support connected networks of populations by building redundancy and resiliency within metapopulations. Coordinated efforts among stakeholders that focus on identifying the management techniques that support necessary habitat conditions with minimal impacts to the remaining individuals, and work towards developing capacity for captive breeding programs for reintroducing the species to suitable areas near the existing populations, may be crucial to stabilizing the AGS populations.