The status and distribution of ( idalia) and Monarch (Danaus plexippus) in eastern Wyoming

Madison S. Crawford1 and Lusha Tronstad2

1 Assistant Invertebrate Zoologist, Wyoming Natural Diversity Database, University of Wyoming, Laramie, Wyoming 82071, United States, [email protected]

2 Lead Invertebrate Zoologist, Wyoming Natural Diversity Database, University of Wyoming, Laramie, Wyoming 82071, United States, [email protected], 307-766-3115

Regal Fritillary on Monarch on Lilac Milkweed

Monarch

Suggest Citation: Crawford, M. and L.M. Tronstad. 2020. The status and distribution of Regal Fritillary (Speyeria idalia) and Monarch (Danaus plexippus) butterflies in eastern Wyoming. Report prepared by the Wyoming Natural Diversity Database, University of Wyoming for the Wyoming Governor’s office.

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Abstract Butterflies are one of the most recognized by the public and are in decline. The Regal Fritillary (Speyeria idalia) and the Monarch (Danaus plexippus) are two of the most easily identifiable butterflies in the United States because of their size and distinctiveness. Both are currently petitioned for listing under the U.S. Act. Both butterflies are thought to be declining due to overexploitation, agricultural activities, and urban development. To assess the status and distribution of the Regal Fritillary and the Monarch in eastern Wyoming, we surveyed 90 sites and walked 408 km from mid-June to late August in 2019. We observed 14,760 individuals and identified 50 species of butterflies. Generally, butterflies were more abundant at lower wind speeds and at sites with higher densities of blooms. We observed seven Regal Fritillaries and 26 Monarchs extending from northeastern to southeastern Wyoming. We observed both butterflies in a variety of habitats, but most sightings occurred at locations with grazing. Our results may help resource managers better understand the status and distribution of these pollinators of management concern and establish baseline information on butterflies in eastern Wyoming.

Introduction Insects declined in Europe and North America over the past few decades (Sánchez-Bayo and Wyckhuys, 2019) and continue to decline faster than birds and plants (Thomas et al., 2004). Pollinating insects (e.g., butterflies, bees, flies, and beetles) are of particular concern because of the ecological services they provide in natural environments and to food crops (Lebuhn et al., 2013). Butterflies are among the declining orders (Sánchez-Bayo and Wyckhuys, 2019) potentially due to overexploitation, agricultural activities, and urban development (Maxwell et al., 2016; Sánchez-Bayo and Wyckhuys, 2019). The drastic decline in diversity was first reported in Belgium during 2001 (Maes and Van Dyck, 2001) and has since been observed in several other European countries, as well as across the United States and parts of Asia (Sánchez- Bayo and Wyckhuys, 2019). Currently, 29 butterflies are protected under the U.S. Endangered Species Act (ESA) in the United States (NatureServe Explorer, 2020) and several others are petitioned for listing. Two butterfly species currently petitioned for listing under the U.S. ESA and found in Wyoming are the Regal Fritillary (Speyeria idalia) and the Monarch (Danaus plexippus), both large butterflies in the family .

Regal Fritillary populations in the United States declined by 75-95% since 1990 (Swengel, 2015) and fewer sightings may in part be due to the rapid loss and fragmentation of ecosystems by agriculture (farming and grazing) and grassland fires (Henderson et al., 2018; Moranz et al., 2014). This decline led to the Regal Fritillary being petitioned for listing under the U.S. ESA in 2013 (WildEarth Guardians, 2013) and receiving a substantial 90-day finding in 2015 (U.S. Fish and Wildlife Service, 2015). Historically, the Regal Fritillary occupied much of the eastern United States and are considered prairie specialists (U.S. Fish and Wildlife Service 2013). They occurred along the east coast, from Maine to North Carolina, and extended westward to the eastern boundaries of , Wyoming, and Montana (Selby, 2007). Regal Fritillaries largely disappeared from the eastern portion of their range (Swengel et al., 2011) and the distribution of the Regal Fritillary in Wyoming is largely unknown. Males emerge before females in early summer, they mate, and females lay eggs in the fall. Regal Fritillaries do not migrate, but females are nomadic in late summer. Larvae hibernate in prairies with stable resources (Swengel, 2015) from September to June (Kopper et al., 2001). Interestingly, females do not rely on the presence

2 of their larval host plants, Violets ( spp.), to lay eggs. Regal Fritillaries have high fecundity and lay over 2000 eggs on the underside of leaves (Kopper et al., 2000) increasing the chance of some emergent caterpillars locating Violets by laying many eggs across scattered habitats. Adult Regal Fritillaries prefer high densities of forbs and a diversity of flowering plants (Caven et al., 2017), gravitating towards areas with recent fires because of increased flower production (Ehrenreich and Aikman, 1963). These butterflies generally avoid areas with bare ground, instead preferring land with more litter and lower grazing intensities (Caven et al., 2017).

Similarly, Monarch butterflies were reported to be in decline across their range. Populations of Monarchs in the eastern United States decreased by 80-97% (Rendón-Salinas et al., 2015; The Xerces Society, 2020) and western populations decreased 98% since 1997 (The Xerces Society, 2020). As a result, the Monarch was petitioned for listing under the U.S. ESA in 2014 (The Center for Biological Diversity et al., 2014) and received a substantial 90-day finding the same year (U.S. Fish and Wildlife Service, 2014). The decline of Monarchs may be largely driven by fewer Milkweed (Ascelpias spp.), their larval host plant (e.g., Pleasants and Oberhauser, 2013; Zaya et al., 2017) as well as agricultural intensification and pesticide use (e.g., Stenoien et al., 2018; Crone et al., 2019). Monarchs are well-known for migrating ≤3600 km from summer breeding habitat to overwintering areas in southern Mexico taking about 75 days to make the journey (Brower 1996). They are remarkable in their ability to migrate as the butterflies laying eggs along their route that includes 3-5 generations annually (Brower 1996). Migrating Monarchs east of the Rocky Mountains are well documented and better understood than populations west of the Rocky Mountains (Dingle et al., 2005). In general, eastern inland Monarchs converge in Mexico each fall and Monarchs on the east coast migrate to Florida to overwinter (Knight and Brower 2009). On the other hand, most western populations move to southern California or congregate in Mexico to overwinter. Overwintering sites are much smaller than summer habitat, but the sites must have sufficient amounts of nectar for initiating and completing migration (Alonso-Mejia et al., 1997). As temperatures begin to rise in the spring, Monarchs return to their summer habitats. During the Monarch’s breeding and migration season, they require trees for roosting and Milkweeds to lay eggs. Monarch and Milkweed conservation gained considerable momentum in recent years (Jepsen et al., 2015; Zaya et al., 2017); despite the surge of interest in Monarchs, the current distribution of Monarchs in Wyoming is largely unknown.

Our goal was to estimate the status and distribution of the Regal Fritillary and the Monarch and establish baseline information on butterflies in eastern Wyoming during 2019. Historically, four observations of the Regal Fritillary and zero Monarch sightings were recorded in Wyoming before 2005 (BAMONA, 2019). Our specific questions were 1.) What is the abundance and richness of butterflies in eastern Wyoming?, 2.) How does butterfly abundance and richness relate to habitat conditions?, 3.) How abundant and what was the range of the Regal Fritillary and the Monarch in Wyoming, and 4.) What habitats did we observe the Regal Fritillary and the Monarch in? We surveyed butterflies and measured habitat characteristics at 90 sites in eastern Wyoming from mid- June to late August 2019. Our results may help resource managers better understand the status and distribution of these pollinators of management and conservation concern and establish baseline information on butterflies in eastern Wyoming.

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Study Area We surveyed for the Regal Fritillary and the Monarch in eastern Wyoming with sites extending from the northern to the southern border. We visited 90 sites in Albany, Campbell, Converse, Crook, Goshen, Laramie, Niobrara, Platte, and Weston counties (Figure 1) from mid-June to late August. Sites were selected throughout eastern Wyoming to sample a wide range of habitat types mainly on public lands. The primary habitat for Regal Fritillaries typically includes large patches of wet meadows and shortgrass prairie. Secondary habitat includes depressions in the land, the presence of streams, gullies or gulches, and high densities of nectar-rich plants. Tertiary habitat catered to the nomadic nature of Regal Fritillaries and included wooded areas, mixed grass prairies, sagebrush steppes, and riparian areas. A combination of habitat types was surveyed to estimate the distribution and status of the Regal Fritillary and the Monarch in eastern Wyoming.

Methods Two observers walked separate transects at each study site to survey for butterflies. Transect length was largely based on the size of the site. We recorded the length and time used to complete each transect on a GPS unit. Butterflies visible within about five meters of the observer were recorded at the family, subfamily, or species-level. We target netted a few individuals of each species for identification except for Monarchs and Regal Fritillaries which were not collected. Collected specimens were spread and pinned for identification (Kaufman and Brock, 2003) and used to estimate the richness of butterflies in eastern Wyoming.

We collected vegetation and environmental data to assess suitable habitat for the Regal Fritillary and the Monarch. Three vegetation surveys were recorded at three locations along one transect at each study site (n = 9). Plant presence and richness were estimated using a 929 cm2 quadrat. The height of grass and shrubs within the quadrat were measured. Additionally, we counted the number of blooms within the quadrat to estimate flower available to pollinators. Past and current grazing intensity (none, low, medium, or high) were estimated by observing grass from the previous year (past grazing) and the current year as well as other signs of livestock (presence of livestock, tracks, manure, etc.). Air temperature and average wind speed were recorded by a shielded Kestrel 2000 at the beginning of each transect. We recorded any precipitation and estimated percent cloud cover during the transects. We recorded land use as resource extraction (e.g. oil or timber), farming, grazing (e.g. cow, sheep or horse), and recreation.

We used various statistical tests to explain the abundance and richness of butterflies in eastern Wyoming. To standardize butterfly abundance, we divided the number of butterflies encountered during a transect by the distance traveled (butterflies/km). We used the plyr package (Wickham, 2011) to prepare our data for logistic regression, linear regression (lm), chi-squared (Χ2) and analysis of variance (ANOVA). Logistic regression was used to analyze the effects of temperature, wind speed, percent cloud cover, flower abundance, shrub height, and grass height on the presence or absence of the Regal Fritillary and the Monarch. Linear regression was used to analyze the effects of temperature, wind speed, percent cloud cover, flower abundance, shrub height, and grass height on the total abundance and richness of butterflies at each site. Chi-squared test was used to assess the number of sites we observed Regal Fritillary and Monarch butterflies at within each land use and grazing intensity compared to the number of sites we surveyed in each category. We used ANOVA to estimate the effects of precipitation (presence or absence), land use and grazing intensity on total butterfly abundance and richness.

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Results We conducted 166 surveys at 90 sites (Figure 1) that ranged from 0.42 to 6.72 km in length and took 25 to 223 minutes to complete. Surveys were 2.5 km in length and lasted 95 minutes on average. We walked 408 km and 647 hours total during the field season, recording 14,760 butterfly sightings from mid-June to late August. The number of butterflies observed per survey ranged from 0 to 354 individuals and we counted 90 butterflies/km (ranged from 0 to 282) and 6 species (ranged from 1 to 19) per survey on average. comprised 51% of the butterflies (37% Sulphurs and 14% Whites) we encountered along transects, followed by Nymphalidae (30%), Lycaenidae (14%), Hesperiidae (4%), and Papilionidae (1%; Table 1). We identified 52 butterfly species and Nymphalidae (12 genera; 24 species) were the most specious followed by Lycaenidae (4 genera; 9 species), Pieridae (4 genera; 7 species), Hesperiidae (5 genera; 6 species), and Papilionidae (2 genera; 4 species). Of the specimens, the Olympia marble (Euchloe olympia), Mormon Fritillary (), Hoary Comma (Polygonia gracilis), Sagebrush Checkerspot (Chlosyne acastrus), Acmon Blue (Plebejus acmon), Greenish Blue (Plebejus saepiolus), Silvery Blue (Glaucopsyche lygdamus), and Purplish Copper, Lycaena helloides) were collected once. The most commonly collected species were the Clouded Sulphur (), the Checkered White ( protodice), and the Melissa Blue (Plebejus melissa).

Habitat characteristics explained some of the variance in the abundance and richness of butterflies counted. Grass was present at all sites and height ranged from 8.9 to 68.1 cm (mean 30 cm) tall. Mean shrub height was 22.5 cm (4.5 to 96.5 cm), and 29% of sites lacked shrubs. On average, sites featured 4 blooms/m2 though there was much variation (ranged from 0 to 62 blooms/m2), including 25% of sites that lacked blooming flowers. Generally, we observed more butterflies (B; butterflies/km) at sites with more blooming flowers (F; blooms/m2), but flower density only explained 9.5% of the variation (lm, df=77, p<0.003; 퐵 = 4.9 × 퐹 + 77; Figure 2a). We observed more Fritillary butterflies (genus Speyeria, Family Nymphalidae) when grass height (G; cm) was shorter (lm, adjusted R2=0.043, df=77, p=0.036; 퐵 = −0.58 × 퐺 + 13; Figure 2b); however, grass height explained less variance in the richness of butterflies (adjusted R2=0.025, df=68, p=0.102). Similarly, shrub height explained little variation in the number (lm, adjusted R2=-0.016, df=57, p=0.781) and richness (adjusted r2=0.003, df=46, p=0.289) of butterfly sightings. We observed more butterflies/km in rangeland with no past grazing than with medium past grazing (ANOVA, df=3, F=3.5, p<0.02; Tukey HSD p<0.05; Figure 2c); however, land use (ANOVA, df=6, F=0.565, p=0.754), and past (ANOVA, F=0.495, df=3, p=0.689) and current (ANOVA, F=0.105, df=2, p=0.901) grazing intensities had little effect on the richness of butterflies.

Abiotic conditions altered the abundance and richness of butterflies at sites. Mean air temperature was 25ºC (range 5.1 to 39.2 ºC) and mean wind speed was 5.5 km/hr (0 to 22.5 km/hr) during transects. Temperature (lm, adjusted R2=-0.01, df=84, p=0.97) and wind speed (lm, adjusted R2=- 0.01, df=84, p=0.59) explained little variance in butterfly abundance; however, we observed more Fritillary butterflies (lm, adjusted R2=0.08, df=84, p=0.005; 퐵 = −2.7 × 푊 + 10; Figure 3a) and more species of butterflies (R; lm, adjusted R2=-0.66, df=78, p=0.027; 푅 = −0.09 × 푊 + 9.0; Figure 3b) at lower wind speeds (W; km/hr). We also observed more Fritillary butterflies/km during surveys with less cloud cover (C; lm, adjusted R2=0.047, df=84, p=0.024; 퐵 = −0.09 × 퐶 + 9.0; Figure 3c). We seldom encountered precipitation during our surveys (85% of surveys had no precipitation), and precipitation explained little variance in butterfly abundance (ANOVA, df=1, F=0.89, p=0.35) or richness (ANOVA, df=1, F=0.28, p=0.60).

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We observed 7 individuals of the Regal Fritillary at 6 sites from 5 August to 27 August 2019 (Figure 1). The butterfly was present in Goshen, Campbell, Niobrara, and Laramie counties, spanning from the northern to southern boundaries of eastern Wyoming and ~180 km west of the South Dakota and Nebraska borders. Grass (logistic, -0.13, z=-1.038, p=0.299) and shrub height (logistic, =-0.055, z=-0.528, p=0.597) did not explain variance in the Regal Fritillary’s presence, as the butterfly was observed in a variety of habitats with grass ranging from 8.9 to 39.4 cm tall and shrubs fluctuating between 0 and 30.5 cm tall. This butterfly occurred at sites with no flowers (33% of sites), low flower abundance (~1 bloom/m2; 33%), and sites with more flowers (~11 blooms/m2; 33%); therefore, bloom density did not explain Regal Fritillary presence (logistic, zp=0.954). Nearly 79% of sites we surveyed had grazing and most Regal Fritillaries (60%) were observed at locations used for grazing (Table 2). Seventy-five percent of transects where we observed Regal Fritillary were in areas with low to no past grazing compared to 57% percent of transects categorized as such during surveys (Table 3). Eighty percent of transects where we observed Regal Fritillaries were in areas with low to no current grazing compared to 84.2% of transects categorized as such. We were unable to statistically compare the number of observations of Regal Fritillaries to the number of transects in each category (grazing intensity and land use) because the small number of observations made the chi-squared test unstable. Environment factors such as wind speed (logistic, 0.096, z=0.275, p=0.783), temperature (logistic, -0.041, z=-0.0741, p=0.459), cloud cover (logistic, -0.020, z=-1.072, p=0.284), and precipitation (ANOVA, df=1, F= 0.214, p=0.646) did not explain Regal Fritillary abundance during our study. The low number of Regal Fritillaries observed limited our statistical power to detect differences among variables.

We observed 26 Monarchs at 17 sites between 9 July and 29 August 2019 (Figure 1) in Goshen, Campbell, Laramie, Weston, and Crook counties. A single Monarch was observed at 53% of sites where we saw them, two Monarchs were seen at 41% of sites, and we observed three Monarchs at 6% of sites. The Monarch was observed at sites with grass ranging from 21.6 to 32.8 cm tall and with varying shrub heights (0 to 52 cm). We observed Monarchs at sites that had 0 to 13 blooms/m2. Due to much variation and few observations, grass height (logistic, 0.057, z=1.077, p=0.281), shrub height (logistic, -0.038, z=-0.658, p=0.511), and flower density (logistic,  0.001, z=0.418, p=0.676) explained little variance in Monarch sightings. Nearly 79% of sites we surveyed had grazing and most Monarchs (57.1%) were observed at locations used for grazing (Table 2). Eighty-eight percent of transects with Monarchs were in areas with low to no past grazing and 57% of transects surveyed were categorized as such (Table 3). Ninety-four percent of transects with Monarchs had low to no current grazing and 84.2% of transects were categorized as such. We were unable to statistically compare the number of observations of Monarchs to the number of transects in each category (grazing intensity and land use) because the small number of observations made the chi-squared test unstable. Wind speed (logistic, -0.204, z=-0.823, p=0.410), temperature (logistic, -0.05, z=-0.133, p=0.894), cloud cover (logistic, 0.008, z=1.008, p=0.313), and precipitation (ANOVA, df=1, F=1.071, p=0.306) did not explain variance in the butterfly’s occurrences. The low number of Monarchs observed limited our statistical power to detect differences among variables.

Discussion

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We observed Regal Fritillary and Monarch butterflies from the northern to the southern borders of eastern Wyoming. We observed fewer Regal Fritillaries in eastern Wyoming than Monarchs. Before our surveys, four observations of Regal Fritillaries (observation dates unknown) were known in Wyoming; one each in Platte, Goshen, Crook, and Laramie counties (BAMONA, 2019; Selby, 2007). We discovered the Regal Fritillary in two additional counties, Campbell and Niobrara, during our surveys in 2019. Fifteen Monarchs were reported due to the Monarchs and Milkweeds citizen science program statewide between 2014 and 2019 in Goshen, Crook, Laramie, Sweetwater, Albany, Fremont, and Park counties (D. Tuthill, personal communication) and one observation in Sublette County was reported in 2018 (BANOMA 2019). Our surveys in eastern Wyoming discovered Monarchs in two additional counties, Campbell and Weston. The difference in Regal Fritillary and Monarch sightings may in part be due to the predicted limited range of the Regal Fritillary in Wyoming. The western edge of the Regal Fritillary’s range was reported near the eastern border of Wyoming (Kaufman 2003); however, few butterflies studies surveyed eastern Wyoming so the extent to which Regal Fritillaries used Wyoming in the past is not well- established. On the other hand, Monarchs occur across the entire state of Wyoming and likely includes individuals migrating on the western and eastern sides of the Rockies; however, Wyoming is not in the main flyway for either population. Overall, Regal Fritillary and Monarch populations overlapped in eastern Wyoming, and we observed both species at two sites.

Too few observations limited our ability to predict potential Regal Fritillary habitat in Wyoming. Other studies in the midwestern United States reported that Regal Fritillary abundance was positively associated with forbs (Moranz et al., 2014; Caven et al., 2017) and negatively related to shrub cover (Caven et al., 2017; McCullough et al., 2019). We observed the butterfly near Sweet (Melilotus officinalis), Thistle (Cirsium, Onopordum, and Carduus sp.), and (Medicago sativa); however, we did not observe Regal Fritillaries with their larval host plants, Violets. Reports of Regal Fritillary associations with their host plant vary from not dependent (Kopper et al., 2000, 2001; Swengel, 2015) to reliance on Violets. For example, Regal Fritillary were reported to be more reliant on large tracts of grasslands and topographic diversity (e.g. dry mesic grassland and wet mesic grassland; Swengel, 2015), but the top predictors of Regal Fritillary habitat in a random forest model were the presence of Violets, percent forb cover, and habitat isolation (distance/permeability) along the Platte River in Nebraska (Caven et al., 2017). In our study, all sightings of Regal Fritillaries were in August when fewer forbs were flowering and nectar was likely scarcer. Most Regal Fritillary populations peak in July. For example, in Nebraska, 31% of observations were in June, 45% were in July, and 22% of observations were in August (iNaturalist.org, accessed 25 June 2020). We were surprised we did not observe Regal Fritillaries earlier in the summer; however, Wyoming has the second highest mean elevation of any state in the United States (2040 m) which may delay their life cycle. Moreover, we may have observed female Regal Fritillaries traveling through habitats with limited resources because females are more active during late summer (Kopper et al., 2001). Eastern Wyoming is classified as short- grass prairie at the edge of their known range and we observed Regal Fritillaries in low numbers here.

Similarly, too few observations limited our ability to predict potential Monarch habitat in Wyoming. Monarch habitat is primary explained by the presence of Milkweeds (e.g. Pleasants & Oberhauser, 2013; Zalucki & Lammers, 2010; Zaya, Pearse, & Spyreas, 2017); however, we only observed Monarchs with Milkweeds at 8% of sites we saw them. Milkweeds grow in many

7 habitats, including rangeland, agricultural areas, wetlands, prairies, meadows, open-forests, woodlands, and along roadsides (Jepsen et al., 2015; Kasten et al., 2016). Currently, there are 13 species of Milkweed in Wyoming and over 1,000 occurrences in eastern Wyoming (Rocky Mountain Herbarium, 2008), offering opportunities for Monarch’s to lay eggs and travel across the state during their breeding and migrating season. Our infrequent sightings of Monarchs with Milkweeds may be because Monarchs were migrating, only stopping at Milkweeds to feed and lay eggs. Along with the Monarch’s larval host plant, these butterflies require additional resources, such as adequate amounts of nectar for migration (Alonso-Mejia et al., 1997). We observed Monarchs near Sweet Clover, Alfalfa, Gumweed (Grindelia sp.), and Sunflowers (Helianthus spp. and Helianthella spp.), and the butterflies likely used these plants as nectar resources. Furthermore, Monarchs were often observed in habitats with streams, ponds, or wet meadows (55%). Wyoming has Milkweed and nectar resources for the Monarch to breed and migrate, but Wyoming is not in the main migration routes of this iconic butterfly.

In our study, ~60% of Regal Fritillary and Monarch observations were on lands used for livestock grazing. Previous studies reported positive (Swengle and Swengle 2001), neutral (McCullough et al., 2019) and negative (Moranz et al., 2014; Leone et al., 2019) effects of grazing on Regal Fritillary and Monarch abundance. The various effects of grazing on grasslands is well-studied (e.g., Schönbach et al. 2011; McGranahan et al. 2012; Bakker, Blair, and Knapp 2003) and depend on many variables such as productivity (e.g., Olff and Ritchie, 1998), livestock species (e.g, Stewart and Pullin 2008), timing (DeBano et al., 2016) and intensity (e.g., Schönbach et al., 2011; Tadey 2015; Sara et al., 2019). No wonder such varied effects of grazing are reported for Regal Fritillary abundance with so many variables to consider. In general, butterflies are often more abundant and more diverse in areas with more flowers (e.g., Ries et al., 2001; Kurylo et al., 2020) and grazing can increase forb abundance in some situations (Stahlheber and D’Antonio 2013). Most sites we surveyed were on public lands and very few had high grazing intensities. Most observations of Regal Fritillaries and Monarchs were on grazed lands; however, the small number of observations limited our inference. Well-managed rangelands may offer suitable habitat for Regal Fritillary and Monarch butterflies in eastern Wyoming.

Wyoming is home to 238 butterfly species and we encountered ~22% of those species while conducting our surveys in the eastern portion of the state. Out of the 76 genera that reside in the state, we identified 28 genera (37%). The smaller proportion of diversity in our surveys may in part be due to only sampling the eastern part of the state and focusing on prairie habitats. The ecoregions in eastern Wyoming include the High Plains, the Northwestern Great Plains, and the Wyoming Basin (UWYO Extensions, 2020). These features translate to mostly lower elevations ranging from 1,400 to 1,700 m (Knight et al., 2014). Major vegetation types we sampled included sagebrush shrubland and grasslands. In contrast, western and central Wyoming is higher in elevation (mean 2,000 to 2,300 m) and has more mountainous terrain consisting of coniferous forests and alpine tundra in addition to grasslands and shrublands. Because of our focused surveys, we likely encountered fewer butterfly species. Moreover, we started our surveys in mid-June to target the Regal Fritillary’s life cycle and may have missed butterflies that are active in early spring, such as the Mourning Cloak (Nymphalis antiopa). We are not aware of any studies that estimated the abundance and richness of butterflies in eastern Wyoming. A literature review revealed eight journal articles that reported information on butterflies in Wyoming (Web of Science, searched Wyoming and butterfl* or ; access 12 July 2020). Of these articles,

8 four studied genetics, and all studied either one or two species and were on species in mountainous areas (Owen and Wiegert 1985; Debinski 1994; Britten et al., 1994; Bowers and Williams 1995; Auckland et al. 2004; DeChaine and Martine 2005; McCoy et al., 2014; Szcodronski et al., 2018). Therefore, more baseline information on the butterfly communities of prairie habitats in Wyoming are needed to assess change.

Butterflies require plant resources from their larval stage through adulthood. Adult butterflies feed on plant sap, fruit juices, and nectar, though most adults prefer nectar from flowering plants (Willmer, 2011). Butterflies and nectar resources are positively related (Curtis et al., 2015) as we observed in eastern Wyoming. Moreover, butterflies are weak fliers and tend to land and feed on large flowers or flowers in a group (Corbet, 2000). Therefore, as flower density increases, butterflies have more opportunities to land and feed. Larval host plants can often predict the presence of butterfly species with diet restrictions, low mobility, or habitat specialization (Curtis et al., 2015). However, Regal Fritillary presence is not typically dependent on Violets (Kopper et al., 2000, 2001) because they do not use the presence of Violets to lay eggs and we never observed them together. Regal Fritillaries can feed on nectar from a variety of plants, and Thistles and Milkweed were the mostly commonly used nectar sources (Selby 2007). Conversely, Monarchs are specialist because they only lay eggs on Milkweeds and primarily feed on Milkweed as caterpillars. Therefore, the presence of Monarchs is usually associated with these plants (Pocius et al., 2017); however, adults can use nectar from a variety of blooming plants. The abundance and richness of butterflies in Wyoming may be heavily dependent on the presence of adequate floral resources. Wyoming’s abundant grasslands may provide suitable habitat for many butterflies.

All butterflies are active during the day and prefer mild weather conditions (Willmer, 2011). Most of our sampling occurred on clear days with no precipitation because butterflies are known to be highly sensitive to weather and climate conditions (Dennis, 1993); however, we sampled during various wind speeds, cloud coverage, and temperatures. We observed fewer Fritillaries and butterfly species at higher wind speeds as has been reported in other areas (Brattström et al., 2008). Wyoming is the 4th windiest state in the United States (mean 9.3 m/s; World Media Group n.d.) so surveying during low wind conditions can be difficult. Larger butterflies, such as Fritillaries, are probably more affected by the wind than smaller species because of their larger wings. Cloud coverage can reduce butterfly flight (Cormont et al., 2011), and we found more Fritillary butterflies when cloud cover was low, perhaps because mild weather conditions are often associated with clear skies. The Regal Fritillary and the Monarch were observed at a variety of temperatures, but most observations occurred during relatively low wind speeds (most <1.3 m/s). Although we did not find a relationship between butterfly abundance and temperature, butterflies are typically more active and fly longer distances as temperature increases (Cormont et al., 2011; Delattre et al., 2013). Therefore, all butterfly sampling efforts should focus on warm, still days with no precipitation.

Butterflies have infrequently been surveyed in eastern Wyoming and historic data is largely lacking to compare to present surveys. We collected data on the butterfly community as well as two species of management concern to estimate the status and distribution in eastern Wyoming. Monarchs and especially Regal Fritillaries were observed later in the summer. Well-managed rangelands in Wyoming may offer diverse floral resources for butterflies, including Regal Fritillaries and Monarchs, to feed on. We observed few Regal Fritillary and Monarch butterflies

9 in eastern Wyoming and interestingly, we noted nearly 4x more Monarchs than Regal Fritillaries throughout our surveys. Regal Fritillaries are far more abundant in the midwestern United States and Wyoming is at the edge of the butterfly’s range. Conducting surveys at the edge of a species range is vital because changes in their populations may occur there first or indicate a range shift. We are not aware of any previous studies of Regal Fritillaries in Wyoming likely explaining why the edge of their range varies among sources. We observed Regal Fritillaries ~180 km west of the Nebraska and South Dakota borders. The main flyways of Monarchs are west and east of Wyoming and these butterflies do not appear to be numerous in eastern Wyoming; however, they are present throughout the state. Butterflies should continue to be monitored in Wyoming to further estimate their abundance, suitable habitat and range to create baseline information for future comparisons as well as inform land management decisions.

Acknowledgements We thank Kamaile DeLong, Ryan Burns, Bryan Tronstad, Tresize Tronstad, Joy Handley, Tighe Jones and Katrina Cook for performing surveys for butterflies. Joy Handley, Christy Bell, Kamaile DeLong and Katrina Cook provided comments that improved the manuscripts. We thank the Wyoming State office of the Bureau of Land Management, US Forest Service, Wyoming State Trust Land and private landowners for allowing us to survey on their lands making this study possible. The Wyoming Governor’s Office funded the project.

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References

Alonso-Mejia, A., Rendon-Salinas, E., Montesinos-Patino, E., and Brower, L.P. (1997), Use of lipid reserves by Monarch butterflies overwintering in Mexico: implications for conservation, Ecological Applications, Vol. 7 No. 3, pp 934-947. Auckland, J. N., Debinski, D. M., & Clark, W. R. (2004). "Survival, movement, and resource use of the butterfly Parnassius clodius". Ecological Entomology, 29(2), 139-149. doi:10.1111/j.0307-6946.2004.00581.x Bakker, C., Blair, J.M. and Knapp, A.K. (2003), “Does resource availability, resource heterogeneity or species turnover mediate changes in plant species richness in grazed grasslands?”, Oecologia, Vol. 137 No. 3, pp. 385–391. BAMONA. (2019), “Butterflies and Moths of North America”, available at: https://www.butterfliesandmoths.org (accessed 8 May 2020). Bowers, M. D., & Williams, E. H. (1995). "Variable chemical defense in the checkerspot butterfly Euphydryas gillettii (Lepidoptera, Nymphalidae)". Ecological Entomology, 20(3), 208-212. doi:10.1111/j.1365-2311.1995.tb00449.x Brattström, O., Kjellén, N., Alerstam, T. and Åkesson, S. (2008), “Effects of wind and weather on red admiral, Vanessa atalanta, migration at a coastal site in southern Sweden”, Behaviour, Vol. 76 No. 2, pp. 335–344. Britten, H. B., Brussard, P. F., & Murphy, D. D. (1994). "The pending extinction of the uncompahgre fritillary butterfly". , 8(1), 86-94. doi:10.1046/j.1523- 1739.1994.08010086.x Brower, L.P. (1996), orientation: missing pieces of the magnifient puzzle. Journal of Experimental Biology, Vol. 199, pp. 93-103. Caven, A.J., King, K.C., Wiese, J.D. and Brinley Buckley, E.M. (2017), “A descriptive analysis of Regal Fritillary (Speyeria idalia) habitat utilizing biological monitoring data along the big bend of the Platte River, NE”, Journal of Insect Conservation, Springer International Publishing, Vol. 21 No. 2, pp. 183–205. Corbet, S.A. (2000), “What kinds of flowers do butterflies visist?”, Entomologia Experimentalis et Applicata, Vol. 96, pp. 289–298. Cormont, A., Malinowska, A.H., Kostenko, O., Radchuk, V., Hemerik, L., WallisDeVries, M.F. and Verboom, J. (2011), “Effect of local weather on butterfly flight behaviour, movement, and colonization: Significance for dispersal under climate change”, Biodiversity and Conservation, Vol. 20 No. 3, pp. 483–503. Crone, E.E., Pelton, E.M., Brown, L.M., Thomas, C.C. and Schultz, C.B. (2019), Why are monarch butterflies declining in the West? Understanding the importance of multiple correlated drivers. Ecological Applications, Vol. 29 No. 7, e01975. Curtis, R.J., Brereton, T.M., Dennis, R.L.H., Carbone, C. and Isaac, N.J.B. (2015), “Butterfly abundance is determined by food availability and is mediated by species traits”, Journal of Applied Ecology, Vol. 52 No. 6, pp. 1676–1684. DeBano, S. J., Roof, S. M., Rowland, M. M., & Smith, L. A. (2016). Diet Overlap of Mammalian Herbivores and Native Bees: Implications for Managing Co-occurring Grazers and Pollinators. Natural Areas Journal, 36(4), 458-477. doi:10.3375/043.036.0412

11

Debinski, D. M. (1994). "Genetic diversity assessment in a metapopulation of the butterfly Euphydryas gillettii". Biological Conservation, 70(1), 25-31. doi:10.1016/0006- 3207(94)90295-x DeChaine, E. G., & Martin, A. P. (2005). "Historical biogeography of two alpine butterflies in the Rocky Mountains: broad-scale concordance and local-scale discordance". Journal of Biogeography, 32(11), 1943-1956. doi:10.1111/j.1365-2699.2005.01356.x Delattre, T., Baguette, M., Burel, F., Stevens, V.M., Quénol, H. and Vernon, P. (2013), “Interactive effects of landscape and weather on dispersal”, Oikos, Vol. 122 No. 11, pp. 1576–1585. Dennis, R.L.H. (1993), Butterflies and Climate Change, Manchester University Press. Dingle, H., Zalucki, M.P., Rochester, W.A. and Armijo-Prewitt, T. (2005), “Distribution of the monarch butterfly, Danaus plexippus (L.) (Lepidoptera: Nymphalidae), in western North America”, Biological Journal of the Linnean Society, Vol. 85 No. 4, pp. 491–500. Ehrenreich, J.H. and Aikman, J.M. (1963), “An Ecological Study of the Effect of Certain Management Practices on Native Prairie in Iowa”, Ecological Monographs, Vol. 33 No. 2, pp. 113–130. Henderson, R.A., Meunier, J. and Holoubek, N.S. (2018), “Disentangling effects of fire, habitat, and climate on an endangered prairie-specialist butterfly”, Biological Conservation, Vol. 218 No. October 2017, pp. 41–48. Jepsen, S., Schweitzer, D.F., Young, B. and Sears, N. (2015), “Conservation Status and Ecology of the Monarch Butterfly in the United States”, The Xerces Society for Intvertebrate Conservation, available at: https://www.xerces.org/wp- content/uploads/2015/03/NatureServe-Xerces_monarchs_USFS-final.pdf. Kasten, K., Stenoien, C., Caldwell, W. and Oberhauser, K.S. (2016), “Can roadside habitat lead monarchs on a route to recovery?”, Journal of Insect Conservation, Springer International Publishing, Vol. 20 No. 6, pp. 1047–1057. Kaufman, K. and Brock, J.P. (2003), Field Guide to Butterflies of North America, Houghton Mifflin Harcourt Publishing Company, New York. Knight, D.H., Jones, G.P., Reiners, W.A. and Romme, W.H. (2014), Mountains and Plains: The Ecology of Wyoming Landscapes, Second., Yale University Press, New Haven and London. Kopper, B.J., Charlton, R.E. and Margolies, D.C. (2000), “Oviposition site selection by the regal fritillary, Speyeria idalia, as affected by proximity of violet host plants”, Journal of Insect Behavior, Vol. 13 No. 5, pp. 651–665. Kopper, B.J., Margolies, D.C. and Charlton, R.E. (2001), “Life History Notes on the Regal Fritillary , Speyeria idalia ( Drury ) ( Lepidoptera : Nymphalidae ), in Kansas Tallgrass Prairie”, Journal of the Kansas Entomological Society, Vol. 74 No. 3, pp. 172–177. Kurylo, J. S., Threlfall, C. G., Parris, K. M., Ossola, A., Williams, N. S. G., & Evans, K. L. "Butterfly richness and abundance along a gradient of imperviousness and the importance of matrix quality". Ecological Applications. doi:10.1002/eap.2144 Lebuhn, G., Droege, S., Connor, E.F., Gemmill-Herren, B., Potts, S.G., Minckley, R.L., Griswold, T., et al. (2013), “Detecting Insect Pollinator Declines on Regional and Global Scales”, Conservation Biology, Vol. 27 No. 1, pp. 113–120. Leone, J.B., Larson, D.L., Larson, J.L., Pennarola, N. and Oberhauser, K. (2019), “Adult Monarch (Danaus plexippus) Abundance Is Higher in Burned Sites Than in Grazed Sites”, Frontiers in Ecology and , Vol. 7 No. November, pp. 1–13.

12

Maes, D. and Van Dyck, H. (2001), “Butterfly diversity loss in Flanders (north Belgium): Europe’s worst case scenario?”, Biological Conservation, Vol. 99 No. 3, pp. 263–276. Maxwell, S.L., Fuller, R.A., Brooks, T.M. and Watson, J.E.M. (2016), “Biodiversity: The ravages of guns, nets and bulldozers”, Nature, Vol. 536 No. 7615, pp. 143–145. McCoy, R. C., Garud, N. R., Kelley, J. L., Boggs, C. L., & Petrov, D. A. (2014). "Genomic inference accurately predicts the timing and severity of a recent bottleneck in a nonmodel insect population". Molecular Ecology, 23(1), 136-150. doi:10.1111/mec.12591 McCullough, K., Albanese, G., Haukos, D. A., Ricketts, A. M., & Stratton, S. (2019). Management regime and habitat response influence abundance of regal fritillary (Speyeria idalia) in tallgrass prairie. EcoSphere, 10(8). doi:10.1002/ecs2.2845 McGranahan, D.A., Engle, D.M., Wilsey, B.J., Fuhlendorf, S.D., Miller, J.R. and Debinski, D.M. (2012), “Grazing and an invasive grass confound spatial pattern of exotic and native grassland plant species richness”, Basic and Applied Ecology, Elsevier, Vol. 13 No. 8, pp. 654–662. Moranz, R.A., Fuhlendorf, S.D. and Engle, D.M. (2014), “Making sense of a prairie butterfly paradox: The effects of grazing, time since fire, and sampling period on regal fritillary abundance”, Biological Conservation, Elsevier, Vol. 173, pp. 32–41. NatureServe Explorer. (2020), “Version 2”, available at: NatureServe Explorer (accessed 5 May 2020). Olff, H. and Ritchie, M.E. (1998), “Effects of herbivores on grassland plant diversity”, Trends in Ecology and Evolution, Vol. 13 No. 7, pp. 261–265. Owen, D. F., & Wiegert, R. G. (1985). "A southward movement of the painted lady butterfly in Wyoming". Southwestern Naturalist, 30(1), 158-159. doi:10.2307/3670675 Pleasants, J.M. and Oberhauser, K.S. (2013), “Milkweed loss in agricultural fields because of herbicide use: Effect on the monarch butterfly population”, Insect Conservation and Diversity, Vol. 6 No. 2, pp. 135–144. Pocius, V.M., Debinski, D.M., Pleasants, J.M., Bidne, K.G., Hellmich, R.L. and Brower, L.P. (2017), “Milkweed matters: Monarch butterfly (Lepidoptera: Nymphalidae) survival and development on nine midwestern milkweed species”, Environmental Entomology, Vol. 46 No. 5, pp. 1098–1105. Rendón-Salinas, E., Fajardo-Arroyo, A. and Avera-Alonso, G. (2015), “Forest surface occupied by monarch butterfly hibernation colonies in December 2014”, World Wildlife Fund Report, pp. 1–4. Ries, L., Debinski, D.M. and Wieland, M.L. (2001), “Value of Roadside Prairie Restoration to Butterfly Communities”, Society for Conservation Biology Conservation, Vol. 15 No. 2, pp. 401–411. Rocky Mountain Herbarium. (2008), “RM Herbarium Specimen Database”, available at: https://rmh.uwyo.edu/data/search.php (accessed 14 May 2020). Sánchez-Bayo, F. and Wyckhuys, K.A.G. (2019), “Worldwide decline of the entomofauna: A review of its drivers”, Biological Conservation, Vol. 232, pp. 8–27. Schönbach, P., Wan, H., Gierus, M., Bai, Y., Müller, K., Lin, L., Susenbeth, A., et al. (2011), “Grassland responses to grazing: Effects of grazing intensity and management system in an Inner Mongolian steppe ecosystem”, Plant and Soil, Vol. 340 No. 1, pp. 103–115. Selby, G. (2007), Regal Fritillary (Speyeria Idalia Drury): A Technical Conservation Assessment, available at: http://www.fs.fed.us/r2/projects/scp/assessments/regalfritillary.pdf.

13

Stewart, G. B., & Pullin, A. S. (2008). The relative importance of grazing stock type and grazing intensity for conservation of mesotrophic 'old meadow' pasture. Journal for Nature Conservation, 16(3), 175-185. doi:10.1016/j.jnc.2008.09.005 Stenoien, C., Nail, K.R., Zalucki, J.M., Parry, H., Oberhauser, K.S., and Zalucki, M.P. (2018), Monarch in decline: a collateral landscape-level effect of modern agriculture. Insect Science, Vol. 25, pp. 528-541. Swengel, A. (2015), Comments to USFWS on Petition to List Regal Fritillary Federally. Swengel, A.B. (1998), “Effects of management on butterfly abundance in tallgrass prairie and pine barrens”, Biological Conservation, Vol. 83 No. 1, pp. 77–89. Swengel, S.R., Schlicht, D., Olsen, F. and Swengel, A.B. (2011), “Declines of prairie butterflies in the midwestern USA”, Journal of Insect Conservation, Vol. 15 No. 1, pp. 327–339. Swengel, A. B. (2001). A literature review of insect responses to fire, compared to other conservation managements of open habitat. Biodiversity and Conservation, 10(7), 1141- 1169. doi:10.1023/a:1016683807033 Szcodronski, K. E., Debinski, D. M., & Klaver, R. W. (2018). "Occupancy modeling of Parnassius clodius butterfly populations in Grand Teton National Park, Wyoming". Journal of Insect Conservation, 22(2), 267-276. doi:10.1007/s10841-018-0060-1 Tadey, M. (2015). "Indirect effects of grazing intensity on pollinators and floral visitation". Ecological Entomology, 40(4), 451-460. doi:10.1111/een.12209 The Center for Biological Diversity, Center for Food Safety, The Xerces Society and Brower, L. (2014), Petition to Protect the Monarch Butterfly (Danaus Plexippus Plexippus). The Xerces Society. (2020), “Xerces Society for Insect Conservation”, available at: https://xerces.org (accessed 8 May 2020). Thomas, J.A., Telfer, M.G., Roy, D.B., Preston, C.D., Greenwood, J.J.D., Asher, J., Fox, R., et al. (2004), “Comparative Losses of British Butterflies, Birds, and Plants and the Global Extinction Crisis”, Science, Vol. 303 No. 5665, pp. 1879–1881. U.S. Fish and Wildlife Service. (2013), Species Assessment for Regal Fritillary. U.S. Fish and Wildlife Service. (2014), Endangered and Threatened Wildlife and Plants; 90-Day Findings on Two Petitions, Federal Register, Vol. 75, available at:https://doi.org/10.1016/0196-335x(80)90058-8. U.S. Fish and Wildlife Service. (2015), Endangered and Threatened Wildlife and Plants; 90-Day Findings on 25 Petitions, Federal Register, Vol. 80, available at:https://doi.org/10.1016/0196-335x(80)90058-8. UWYO Extensions. (2020), “Wyoming Rangelands”, Wyoming Ecoregions, available at: https://uwyoextension.org/uwrange/rangeland-resources/wyoming-ecoregions/ (accessed 14 May 2020). Wickham, H. (2011), “The Split-Apply-Combine Strategy for Data Analysis”, Journal of Statistical Software, Vol. 40 No. 1, pp. 1–29. WildEarth Guardians. (2013), Petition to List the Regal Fritillary (Speyeria Idalia) Under the Endangered Species Act. Willmer, P. (2011), “Pollination by Butterflies and Moths”, Pollination and Floral Ecology, Princeton University Press, Princeton, pp. 322–331. World Media Group. (2020), “U.S. Average Wind Speed State Rank”, available at: http://www.usa.com/rank/us--average-wind-speed--state-rank.htm (accessed 15 May 2020). Zalucki, M.P. and Lammers, J.H. (2010), “Dispersal and egg shortfall in Monarch butterflies:

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What happens when the matrix is cleaned up?”, Ecological Entomology, Vol. 35 No. 1, pp. 84–91. Zaya, D.N., Pearse, I.S. and Spyreas, G. (2017), “Long-term trends in midwestern milkweed abundances and their relevance to monarch butterfly declines”, BioScience, Vol. 67 No. 4, pp. 343–356.

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Table 1: Butterflies collected in eastern Wyoming from mid-June through August 2019. We surveyed 90 sites and walked 408 km of transects.

Scientific Name Abundance Hesperiidae 98 Atalopedes 5 campestris 5 Epargyreus 2 clarus 2 Hesperia 7 juba 3 uncas 4 Pholisora 10 catullus 10 Pyrgus 70 communis 70 Lycaenidae 176 Glaucopsyche 1 lygdamus 1 Lycaena 13 dione 5 helloides 1 hyllus 7 Plebejus 155 acmon 1 icarioides 19 melissa 122 saepiolus 1 Strymon 5 melinus 5 Nymphalidae 425 Aglais 2 milberti 2 Cercyonis 75 oetus 11 pegala 64 Chlosyne 25 acastus 1 gorgone 24 Coenonympha 15 tullia 15 Danaus 26 plexippus 26 (not collected) Erebia 5 episodea 5 Euphydryas 13

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anicia 13 Euptoieta 47 claudia 47 Oeneis 2 uhleri 2 Phyciodes 111 cocyta 15 pulchella 3 tharos 88 Polygonia 1 gracilis 1 Speyeria 66 aphrodite 19 callippe 3 coronis 4 cybele 2 edwardsii 16 hesperis 21 idalia 7 (not collected) mormonia 1 Vanessa 53 atalanta 2 cardui 42 virginiensis 6 Papilionidae 19 Papilio 9 eurymedon 3 polyxenes 2 rutulus 4 Parnassius 10 smintheus 10 Pieridae 484 Colias 343 alexandra 9 eurytheme 66 philodice 268 Euchloe 1 olympia 1 3 rapae 3 Pontia 137 occidentalis 5 protodice 131

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Table 2. The number and percent of sites where Regal Fritillary (Regal) and Monarch butterflies were observed in different land uses compared to the percent of sites we surveyed in each category (all sites). Several sites had multiple uses and add up to greater than 100%. The number of observations does not add to the total observed if the categories were not assessed due to various reasons.

Land use Regal Monarch All sites Farming 1 (20%) 2 (14.3%) 2.8% Grazing 3 (60%) 8 (57.1%) 78.7% Recreation 0 3 (21.4%) 24.1% Resource extraction 1 (20%) 1 (7.1%) 13.0%

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Table 3. The number of transects and percent of transects where Regal Fritillary (Regal) and Monarch butterflies were observed in none, low, medium and high past and current grazing intensities compared to the percent of transects we surveyed in each category (all sites). The number of observations does not add to the total observed if the categories were not assessed due to various reasons.

Past grazing Regal Monarch All sites None 2 (50%) 6 (35.3%) 20.5% Low 1 (25%) 9 (53.0%) 36.5% Medium 0 (0%) 2 (11.7%) 33.3% High 1 (25%) 0 (0%) 9.6 Current grazing None 2 (40%) 13 (76.5%) 66.0% Low 2(40%) 3 (17.6%) 18.2% Medium 1 (20%) 1 (5.9%) 12.6% High 0 (0%) 0 (0%) 3.1%

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Figure Legends Figure 1: We visited 90 sites from mid-June to late August 2019 where two people walked transects to survey for butterflies. We observed 7 Regal Fritillaries at 6 sites and 26 Monarch butterflies at 17 sites.

Figure 2: (a) The abundance of butterflies/km was positively associated with blooms/m2 whereas the (b) abundance of Fritillaries/km was negatively associated with grass height. (c) More butterflies/km were observed on land without past grazing compared to moderately grazed sites.

Figure 3: (a) The abundance of Fritillaries/km and (b) the richness of butterflies/km was negatively related to wind speed. (c) We usually observed more Fritillaries on days with less cloud cover.

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Figures

Figure 1

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Figure 2

a b

c

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Figure 3

a b

c

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