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Article Title

Large-Scale Migrations of the Painted Lady Butterfly, Vanessa cardui (Lepidoptera: Nymphalidae), in Inyo County, California, during 1991

Volume

94

Issue

2

First Page

149

Last Page

168

Abstract

Detailed observations on significantly large migrations of Vanessa car- dui during 1991 in Inyo County, California, are presented, with special emphasis on their complex behavioral activities. The build up and mass exodus at a pop- ulation center near Bishop are chronicled and provide insights into why some butterflies migrate. A directional shift from northward to southward migration occurred during the summer. The migration phenomenon in this species appears to be dependent upon larval stress subsequently influencing adult juvenile hor- mone levels. This behavior likely evolved during the Upper Miocene as an ad- aptation to avoid seasonally unfavorable arid conditions.