Butterfly Migrations in Florida: Seasonal Patterns and Long-Term Changes

Abstract

Flight traps at Gainesville, in north-central Florida, operating from 1984 to spring 2000, separated butterflies migrating into the Florida peninsula (SSE ± 90°) from those migrating out of the Florida peninsula (NNW ± 90°). Five species flew southward in the fall and northward in the spring: Phoebis sennae (L.), Agraulis vanillae (L.), Junonia coenia (Hübner), Urbanus proteus (L.), and Eurema lisa (Boisduval & LeConte). Five species had significant northward flights in spring but no significant migration in fall: Pieris rapae (L.), Vanessa virginiensis (Drury), Vanessa atalanta (L.), Eurytides marcellus (Cramer), and Libytheana bachmanii (Kirtland). Danaus plexippus (L.) had a southward flight in fall but no significant migration in spring. Eurema daira (Godart) switched from a net movement northward in early fall to a net movement southward in late fall, whereas Eurema nicippe (Cramer) maintained a net movement northward throughout the fall. The major migrants differed significantly in the seasonal timing and duration of peak migration. When the numbers trapped were greatest, the proportion of those flying in the migratory direction was greatest. The numbers of spring migrants of A. vanillae increased during the course of the study, whereas both the spring and fall migrations of J. coenia declined. The fall migrations of P. sennae and U. proteus declined sharply. In 1990–1999, the fall migrations of P. sennae and U. proteus averaged only 37 and 15% of what they had averaged in 1984–1989. Reduced planting of soybeans in source areas for migrants probably contributed to these steep declines.