North American Range
The North American subspecies is Vanessa atalanta rubria (Fruhstorfer, 1909). The original common name in English was “Red Admirable”. Fast, erratic fliers, these butterflies are known to engage in periodic mass migrations north in the spring and early summer, but the huge migrations are often followed by population crashes. Males perch on ridge and hill tops in the afternoon to wait for females, who lay eggs singly on the tops of hostplant leaves. Young caterpillars live within a shelter of folded leaves; older caterpillars make a nest of leaves tied together with silk. Because they are not tolerant of cold, most of North America must be recolonized each year from the south.
Upperside is black with white spots near the apex; forewing with red median band, hindwing with red marginal band. The winter form is smaller and duller, summer form larger and brighter with an interrupted forewing band.
In late April migrant adults from southern populations (approximately North Carolina southward) first arrived in Vermont. Adults from the spring brood begin to appear in late June producing a third generation of adult butterflies that flies from late August into October. At least some individuals from this fall generation probably migrate south. Extreme dates: 20 April 2002 in Plainfield (B. Pfeiffer), 20 April 2003 in Berlin (A. Shambaugh), 27 October 1996 in Woodstock (K.P. McFarland), 19 November 1998 in Grand Isle (A. Horvath).
Distribution and Habitat
Because it is a migratory species, its annual abundance in the state fluctuated widely during VBS. Two years were particularly high, with 2003 reporting 23% and 2007 with 57% of the 1,550 Red Admirals reported for VBS. Over the entire survey period, observers reported them from across Vermont. Larval hostplants are in the nettle family and include Stinging Nettle (Urtica dioica), Wood Nettle (Laportea canadensis), and False Nettle (Boehmeria cylindrical). Adults will nectar, but prefer tree sap, fermenting fruit and bird droppings.