An alvar race of the couperi subspecies of the Silvery Blue (Glaucopsyche lygdamus couperi) in southeastern Ontario?


  • Paul M. Catling Agriculture and Agri-Food Canada, Environmental Health, Biodiversity, Saunders Building, Central Experimental Farm, Ottawa, Ontario K1A 0C6
  • Ross A. Layberry 6124 Carp Road, Kinburn, Ontario K0A 2H0



Silvery Blue, Glaucopsyche lygdamus, Glaucopsyche lygdamus couperi, Glaucopsyche lygdamus lygdamus, alvar, Ottawa valley, Neglected Milk-Vetch, Astragalus neglectus, host plant, food plant, distribution, ecology, subspecies, southern Ontario


The couperi subspecies of the Silvery Blue (Glaucopsyche lygdamus couperi) has expanded its range southward in northeastern North America using introduced legumes and open anthropogenic habitats. The discovery of a population of the Silvery Blue (Glaucopsyche lygdamus) in an eastern Ontario alvar woodland in 2011 suggests that the Silvery Blue may have been long established (although restricted) in southern Ontario. Three larvae from this population were reared from eggs deposited on native Neglected Milk-Vetch (Astragalus neglectus) by free-flying females in 2012. The three larvae, pupae, and single reared adult, as well as other adults from the alvar woodland, are described and compared with specimens associated with open anthropogenic habitat and introduced legumes. The alvar woodland specimens were closer to the northern Ontario subsp. couperi than to the subsp. lygdamus of the eastern United States. Although the alvar woodland larvae were darker green than subsp. couperi and the spots on the adults were on average larger than in subsp. couperi, the alvar woodland Silvery Blues could not be definitively distinguished from subsp. couperi, including specimens from northern Ontario and those from southern Ontario associated with open habitats. Nevertheless, there is a possibility that the alvar woodland population of the Silvery Blue dates from early postglacial times and represents a distinct race separate from the Silvery Blue of open habitats.