Orientation and reproductive condition of migrating dragonflies (Anisoptera)

From equatorial Uganda and southern Canada the behaviour and reproductive condition of migrating Anisoptera are described. In neither situation was sexual activity seen among migrating adults. In Uganda, a very large Bight of Anisoptera, predominantly Hemianax ephippiger, descended at sunset from a great height, roosted overnight and then left at sunrise. Females among these H. ephippiger were unmated, very immature reproductivcly, and richly endowed with abdominal fat. They, and 2 other spp. accompanying them, probably began migrating in the early post-teneral stage. In Canada, aggregations of Anisoptera. mainly Anax Junius, were observed as they roosted in Aug. and Sept, on their way south. Adult A. junius roost on west-facing vegetation but exhibit a brief, pre-sunrise adjustment flight by which they move to east-facing perches that relatively quickly become warm. It is suggested that not only migrants may benefit from such a translocation early in the morning; moreover it may be useful for orientation during migration, whether or not it is necessitated by low ambient temperature. All (female) Tramea lacerata. ulmost all A. junius and most Pantala flavescens examined from these aggregations were immature reproductively and almost all Sympetrum vicinum were mature. Abdominal fat correlates moderately well with ovarian immaturity in A. iuniux but not in the .1 other spp, examined.