Timing of Karner Blue (Lepidoptera: Lycaenidae) Larvae in Spring and Adults in Spring and Summer in Wisconsin During 1991-1998

During 1991-1998, formal surveys and incidental observations of the Karner blue (Lycaeides melissa samuelis) (Lepidoptera: Lycaenidae) occurred on 2-8 dates each year for spring larvae and on 5-10 dates in each adult gen­ eration at 148 pine-oak barrens in ten counties of central and northwestern Wisconsin. A total of 493 spring larvae were recorded, as well as 16,039 adults (6755 in spring and 9284 in summer) in 375.5 hours of formal adult survey effort. Adult Karner blue timing varied among years by about 2-5 weeks in spring and 2.5-6 weeks in summer. The mean span between spring and summer adult generations was about 46 to 50 days for all sites pooled. In some years, Karner blue phenology appeared to "speed up" or "slow down" relative to this average span between generations. At six sites surveyed for spring and summer adults in the same 5 years, the mean date of maximum adults differed among sites by about 9.5 days in spring and 6 days in sum­ mer. These sites varied in the consistency of their relative phenology (early, average, or late) between spring and summer. Consistent sites changed rela­ tively little in shading from spring to summer because canopy was sparse or primarily evergreen. Variable sites changed in degree of insolation between spring and summer, because of the leafing out of deciduous canopy or the higher angle of the summer sun rising above the surrounding forest more. Four kinds of variability should be considered in assessments of Karner blue phenology: (1) intergenerational fluctuations in abundance, (2) phenological differences among years and (3) among sites, and (4) interannual variation in span between spring and summer generations. Restricted to eastern North America, the Karner blue (Lycaeides melissa samuelis Nabokov) is federally listed as endangered in the USA and consid­ ered extirpated in Canada. This butterfly has two complete life cycles per year, feeds only on wild lupine (Lupinus perennis L., Fabaceae) as a larva throughout its range, overwinters as an egg, and has a rather n rrow gener­ ally east-west historical range at the northern end oflupine range, from east­ ern Minnesota through the Great Lakes states and southern Ontario to New England (Iftner et al. 1992, Bleser 1993, Dirig 1994, Packer 1994, Savignano 1994). Surveying and monitoring are necessary components of conservation pro­ grams for rare or declining butterfly species (Pollard 1977, Thoma 1983, New 1993, Pollard and Yates 1993). As a result, much effort in the U.s.A. 1909 Birch Street, Baraboo, Wisconsin 53913 USA 1 Swengel and Swengel: Timing of Karner Blue (Lepidoptera: Lycaenidae) Larvae in Spring Published by ValpoScholar, 1999 80 THE GREAT LAKES ENTOMOLOGIST Vol. 32, No.1 & 2 and Canada is devoted to surveying and monitoring Karner blues (e.g., many chapters in Andow et a1. 1994, Brown and Boyce 1998). But depending on seasonal progress, the timing of butterfly life stages-and thus, appropriate timing for field surveys-may vary among years (Warren 1992, Glassberg 1993, Pollard and Yates 1993). In this paper, we analyze the date on which we observed various phenologi­ cal vents for Karner blue larvae in spring, and adults in spring and summer, for each year during 1991-1998 in Wisconsin. We provide the means and ranges for these dates as well as the means and ranges for the differences in days between pairs of these dates. We also identify patterns of variation in the timing of Karner blue generations. Such information should prove useful for designing survey procedures to monitor populations of this butterfly.