Pre-tandem and in-tandem courtship in Libellulidae (Anisoptera)

Two types of courtship can be distinguished in odonates: pretandem courtship which is common in several families of Zygoptera, and in-tandem courtship which is a feature of some Zygoptera and occurs in at least a few Libellulidae. In both types the female has the option of refusing or accepting copulation, and even after copulation she has in theory a further option on the use of a particular male’s sperm. Among Anisoptera, pre-tandem courtship has been described in at most five species of libellulids. Observations on pretandem courtship in Palpopleura lucia lucia and Brachythemis lacustris, made in Zimbabwe, are described here. In both species, courtship may enable males to distinguish receptive from non-receptive females. In B. lacustris, feeding and reproductive behaviour both occur late in the day at the same sites over water, and sexually active males thus encounter numerous immature and unreceptive females as well as receptive females near their territories. Courting males induce receptive females to enter their territories and then hover low over potential oviposition sites before being accepted. B. leucosticta has been observed to be sexually active at the same time and in some of the same places as B. lacustris, but it shows no courtship. This may reflect the fact that, unlike B. lacustris, it does not feed over water. During in-tandem courtship in Zygoptera, the male issues “copulatory invitations” by wing waving and abdominal flexing movements. In some libellulids, for example Orthetrum coerulescens, in-tandem courtship may also occur when a pair makes repeated dipping movements down towards the water, some females perhaps accepting copulation only after they have inspected potential oviposition sites in this way.