In Wisconsin during 1987-1999, we recorded elfin (Callophrys) individuals on 154 of 254 observation dates between 2 April and 11 July. The frosted elfin (C. irus) occurred only in central Wisconsin; brown (C. augustinus), hoary (C. polios), and Henry's (c. henrici) elfins in central and northern Wisconsin; and eastern pine elfin (C. niphon) from southern to northern Wisconsin. Most individuals were eastern pine elfins, which occurred at the most sites, while Henry's elfin had the fewest individuals and sites. All five elfins occurred in the most frequently visited subregion (central Wisconsin), where they all had similar median and mean observation dates for all study years pooled. For most elfins, the number of individuals observed per year covaried significantly with the span of days between first and last observation dates that year. Within species, mean and median observation dates in the earliest year(s) always occurred before the first observation date in the latest year(s). We compared the phenology of the frosted elfin flight period to the timing of olympia marble (Euchloe olympia) adults and spring Karner blue (Lycaeides melissa samuelis) larvae and adults. The least variable relationship was the date of first mature Karner larva (typically before first frosted elfin adult, and bracketing that date by only 8 days). Only the frosted elfin showed a significant influence of weather (temperature only) on observed density, while most elfins significantly increased the nearer to noontime. We recorded elfins in broad ranges of weather conditions and daily timing. Elfin abundance fluctuated markedly among years based on the mean of peak survey totals at the same monitoring sites in central Wisconsin each year from 1992 or 1993 to 1999. One "outlier" site each for frosted and eastern pine elfins had much higher peak survey totals than the other sites. Abundance fluctuations in the outlier and other sites did not correlate significantly for either species. For most elfins, the percent sites where the species was recorded as present each year covaried significantly with that year's annual mean of peak survey totals. This indicates that the ability to document presence of an elfin relates to the species' abundance that year. Since elfin abundance and flight timing and length varied considerably among years, the appropriate time for elfin detection must be determined individually for each year and assessments of an elfin's status and abundance cannot be reliably based on surveys at only a few sites or in a few years.
Swengel, Ann B. and Swengel, Scott R.
"Variation in Timing and Abundance of Elfins (Callophrys) (Lepidoptera: Lycaenidae) in Wisconsin During 1987-1999,"
The Great Lakes Entomologist, vol 33
Available at: https://scholar.valpo.edu/tgle/vol33/iss1/9