Eastern persius duskywing: COSEWIC assessment and status report: chapter 8
Biology
Erynnis p. persiusis a univoltine skipper, although rarely individuals may eclose out of season (NatureServe Explorer 2001). Females oviposit directly on host plants, with single eggs laid on the underside of leaves (Mo Nielsen, pers. comm., 2002). After larvae hatch, they feed exclusively on the host plant and construct rolled-leaf nests for protection while they eat, like other Erynnis species. Feeding ends in July and the late-instar larvae remain in diapause until the following spring, when they pupate (NatureServe Explorer 2001). Adults fly during May and early June, exhibiting the quick flight typical of Erynnis skippers (Mo Nielsen, pers. comm., 2002). Apparently, adults hilltop (i.e., fly up-slope to converge at the top of a hill or ridge to facilitate pairing and mating) (Kirk 1996).
Very little is known regarding the reproduction of this species. Females lay single eggs on host plants. Nothing is reported regarding the species’ fecundity or the survivorship or special requirements of the eggs, besides presence of host plants. Sex ratios in collections are biased toward males, probably reflecting the habits of males vs. females and the ease with which males are captured and identified, rather than true sex ratios. Matt Holder knows of no reports of breeding behaviour, copulation or oviposition in Ontario.
Nothing is known regarding the survivorship of E. p. persius, or its minimum viable population size. Based on the life history of the species, zero recruitment for even one year would have dire consequences for a local population. Populations would be extirpated with any, even short-term, catastrophic event unless they could be rescued by dispersal (the extent of which is unknown) from source populations. In the past, the presence and abundance of host plants in an area largely dictated the health of the population and its recruitment. Other factors, such as weather, fire or disturbance, could have devastating effects. Fire is recognized as especially destructive to E. p. persius populations because of the species’ life history (Kirk 1996); however burned areas can create favourable conditions for recolonization (Maxwell and Ferge 1994). Burns that are of high intensity and over a large scale could be detrimental to this species, while lower intensity burns over a smaller scale could be beneficial to E. p. persius.
This taxon enters diapause as a mature larva in the leaf litter. The temperature and other environmental requirements are unknown, although mature larvae were apparently able to withstand the cold winter temperatures normal for southern Ontario. No studies on the physiology of E. p. persius have been conducted to date.
Very little is known regarding this taxon’s movements. However, specimens have been collected “far” from known lupine or indigo locations (NatureServe Explorer 2001), indicating that the species may be able to disperse to some degree. Kons and Borth (1997) found individuals eight kilometres from the closest known lupine population. Considering the dynamic nature of oak savannah and prairie habitat, E. p. persius is expected to be able to disperse from altered and temporally unsuitable areas and repopulate newly suitable habitats. A spatially structured population or a metapopulation structure is probably the norm for this species (Givnish et al. 1988). However, the spatial scale at which populations link is unknown. Schweitzer (2001) believes this taxon is a “fairly good short range colonizer.”
Although closed forest does not appear to provide a barrier to dispersal, it is unknown what effect urbanization may have on the dispersal of individuals. It is very unlikely extant populations in the United States could become natural sources for Canadian populations. Erynnis p. persius has been found as close as Monroe and Wayne Counties in Michigan, and Genesee County in New York. The closest extant populations of E. p. persius are in Wayne County, Michigan, approximately 150 km from The Pinery Provincial Park (Mo Nielsen, pers.comm., 2005).
Larval E. p. persius are host-specific to wild lupines (L. perennis) and to wild indigo (B. tinctoria) plants, although the former plant is likely its predominant host (Mo Nielsen, pers. comm., 2002). Dale Schweitzer (pers. comm., 2002) believes a third unknown plant is also utilized by E. p. persius because of the skipper's existence at some sites where neither of the two known host species occurs. Although E. p. persius occupies the same habitat as other lupine-feeders, such as L. m. samuelis, and is expected to compete for food with these other species, nothing is known regarding interspecific competition. Adult E. p. persius are generalists with respect to feeding as they nectar at many different flower species. From a herbivory perspective, white-tailed deer may be considered to be a competitor because of this mammal’s preference for eating lupines in spring.
Little is known about the behaviour of E. p. persius. Hilltopping is reported as the skipper’s reproductive strategy (D. Schweitzer, pers. comm., 2002), but no details have been provided. Erynnis. p. persius appears to be restricted in its larval host species (which are themselves rare), and is likely very susceptible to any habitat changes that affect host plant populations. Inappropriate fire regimes may have caused population declines (NatureServe Explorer 2001).
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