Endangered Oarisma poweshiek butterfly larval foraging and adult habitat interactions in Manitoba, Canada

Abstract

The Poweshiek skipperling (Oarisma poweshiek) is endemic to the tall grass prairie in North America, and is now critically endangered globally. Existing populations are scattered amongst tall grass prairie remnants. However, the host food plants eaten by Poweshiek skipperling larvae, the vegetative and microclimatic descriptions of immature and adult microhabitats as well as O. poweshiek behaviour in Manitoba are unknown. I observed the foraging behaviour of larval O. poweshiek in natural habitat to determine the plant species that they consume and document their development. I also followed adults in prairie patches to identify locations in which various activities, such as egg laying or nectar feeding, were facilitated by the habitat. I measured vegetative, structural and microclimatic attributes of microhabitats to determine potential characteristics which facilitate various adult activities and larval development. Larvae appeared to navigate microhabitats to locate host food plant species, alternating between shoots of various species throughout their development. Adults flew almost exclusively in the prairie plant community, rarely flew in shrub or ephemeral wetland communities and were never observed flying in wetland or forest communities. Adult activities appeared to be distributed along a soil moisture gradient, with egg laying associated with the mesic section of the moisture gradient, resting and/or basking associated with the drier section and nectar feeding generally associated with sections throughout the moisture gradient. My research contributes knowledge about larval O. poweshiek foraging and adult habitat interactions in prairies in Manitoba, Canada. Discoveries from my research may guide habitat stewardship to ensure that high quality habitat is available for every life stage and inform reintroduction activities to ensure potential release locations contain required habitat features. Novel descriptions of locations which facilitate larval development and various adult activities may inform provincial and federal recovery strategies to increase the chances of O. poweshiek’s survival. My findings may also initiate further research about the Poweshiek skippering and possibly guide the strategies to recover other Lepidopterans-at-risk. Now with a greater understanding of larval foraging and adult interactions, we may hopefully generate potential causes which explain O. poweshiek’s decline and identify possible solutions to facilitate its successful recovery!

Egg Laying Behaviour and Larval Shelter-Construction Patterns of the Endangered Mottled Duskywing (Erynnis martialis) Butterfly's Western Population in Canada

“…The estimated area of host plants with eggs did not appear to be different than plants without. Multiple Lepidopterans have been reported laying eggs on larger host plants (Robakiewicz & Robbins 2001, Lund et al 2019, possibly to support immediate aspects of their biology (for example, specific microclimates for egg development) while relying on larvae to locate suitable development locations on the host plant (Wiklund 1984, Kopper et al 2000, Henault 2021). We also observed multiple eggs deposited close to one other, perhaps due to multiple females similarly recognizing optimal characteristics for development (P. alcon in Osváth-Ferencz et al 2016 andVilbas et al 2016).…”

“…Adults consumed nectar of several species (most new records in Manitoba), including the larval host plant. Oarisma poweshiek (Parker, 1870) (Hesperiidae, Hesperiinae) nectar feed opportunistically and conduct activities (nectar feed, lay eggs, rest) within prairie areas but not adjacent wetlands or forests (Henault 2021). Similarly, E. martialis may also take advantage of available nectar sources nearby C. herbaceus but not within forest stands.…”

Management practices benefit endangered Poweshiek skipperling (Oarisma poweshiek) in Manitoba tall grass prairie

“…Poweshiek skipperling are prairie specialists that rely on native wet-mesic and dry prairie habitat (Catling and Lafontaine 1986;Selby 2005), with adults feeding on forb species primarily associated with dry prairie and larvae feeding on graminoid species primarily associated with wet prairie (Henault and Westwood 2019). They are rarely found in non-native vegetation (Swengel and Swengel 1999;Henault and Westwood 2022;Henault and Westwood 2023).…”

“…The timing of life cycle stages varies across the species' range and between years depending on weather (Selby 2005). In Manitoba, the brief adult flight period occurs from late June to late July, during which time eggs are laid on host plant leaves (Henault and Westwood 2019;Henault and Westwood 2022). Host plants in Manitoba include grasses such as big bluestem (Andropogon gerardii Vitman), mat muhly (Muhlenbergia richardsonis (Trin.)…”

“…Gray) B. Boivin) have been the primary nectar plants of adults in Manitoba (Catling and Lafontaine 1986;Semmler 2010;Dupont Morozoff 2013;Westwood et al 2020), though Poweshiek skipperling have recently been observed nectaring on other species (Henault 2021). Catling and Lafontaine (1986) observed the highest Poweshiek skipperling densities in areas with high pale-spiked lobelia densities, but pale-spiked lobelia was not present during Semmler (2010) and Dupont Morozoff's (2013) studies and was also scarce in Henault's (2021) study. In Michigan, Poweshiek skipperling are more likely to be found in areas with high numbers of their preferred nectar plants (Belitz et al 2019).…”