MASSIVE SWARM MIGRATIONS OF DRAGONFLIES (ODONATA) IN EASTERN NORTH-AMERICA

We describe massive autumn migrations of dragonflies (Odonata) which o ccurred at Chicago, Illinois (14 September 1978), Cape May, New Jersey (ll September 1992), and Crescent Beach, Florida (3-5 September 1993) . Estimated numbers of migrant dragonflies involved in these flights w ere approximately 1.2 million, >400,000, and 200,000, respectively We also document other recent observations of large swarm migrations of d ragonflies in eastern North America, review previous reports of this p henomenon, and compare these events to the flights at Chicago, Cape Ma y and Crescent Beach. Records of large drag onfly migrations show seve ral distinct patterns: (1) all reports fell between late July and mid- October, with a peak in September; (2) most of the large flights occur red along topographic leading lines such as coastlines and lakeshores; (3) massive swarm migrations generally followed the passage of synopt ic-scale cold fronts; and (4) the common green darner (Anax junius) wa s the principal species involved in the majority of these flights. Str iking parallels between the patterns of seasonal timing, geographical distribution, and meteorological context of dragonfly migrations and t hose of birds suggest that similar causal factors are involved.