Karner Blue - Life History and Reproduction

Life History and Reproduction

Karner blue butterflies have two broods per year, following wild lupine (Lupinus perennis) phenology quite closely. Eggs laid by Karner blue butterflies in late summer overwinter and hatch in mid- to late April. Development from egg through four larval instars and pupation takes from 25 to 60 days. The average lifespan of adult Karner blue butterflies has been reported at between 3 and 5 days. The first Karner blue butterfly flight generally occurs sometime between mid-May and mid-June, with males typically appearing earlier than females. First flight females lay the vast majority of their eggs on wild lupine. These eggs develop into the adults of the second Karner blue butterfly flight, which generally occurs in July and August. Although always near a wild lupine plant, second brood females lay more eggs on grasses, other plants, and litter than 1st brood females. The 2nd flight is typically two to four times the size of the first flight. However, the first flight of Karner blue butterflies can be larger than the second. Timing and size of both flights can exhibit substantial variation, depending on local weather conditions among other factors.

A wide range of values related to Karner blue butterfly recruitment have been reported. Adult Karner blue sex ratios vary from 1 male to 1.44 females to 2 males to 1 female. Wild caught Karner blue butterfly females have been observed to lay from 7.7 to 83 eggs on average. Reported percentages of eggs that reach adulthood under controlled conditions vary from 21.4% to 75.2%. In the wild, loss of eggs may be substantial.

Karner blue butterflies do not typically move vary far, with males usually moving further than females, with most studies showing average distances moved by individual butterflies of well under 1,000 feet (300 m).