Wing Damage in Overwintering Populations of Monarch Butterfly at Two California Sites

Abstract

Overwintering monarch butterflies collected from two California sites did not show a progressive wing deterioration. Butterflies collected earlier in the season showed magnitude of wing area loss (≈2%) similar to that in butterflies collected later in the season. Wing damage frequencies attributed to wing area loss among males increased significantly in March and were associated with mating activity. Females did not show this increase in wing damage frequency but had a significantly greater total wing area loss than males. Although hind wings were damaged more frequently than forewings, the amount of missing wing area was not significantly different.