Pre-copulatory guarding and other aspects of reproductive behaviour in Sympetrum depressiusculum (Selys) at rice fields in southern France (Anisoptera: Libellulidae)

Sexually mature male and female S. depressiusculum were observed in large swarms throughout the day at or near rice fields in the Camargue, southern France, in July, 1983. Males became active 19 min before sunrise when they formed tandems with roosting females. Tandem pairs remained perching on rice plants and adjacent grass with only occasional changes of position for 2'/,-3 hours, after which copulation and oviposition commenced. No territorial behaviour or other interaction between single males was observed, but on a few occasions single males were seen unsuccessfully to attempt to seize females in tandem. Many further pairs in tandem flew into the rice fields from neighbouring meadows throughout the morning; they either rested or commenced to copulate and oviposit soon after arrival. Copulations were commonly preceded by dipping movements which resembled aerial oviposition in other species but were without egg release. Dipping may enable females to verify the presence of an oviposition site, before accepting copulation. Unsuccessful attempts to copulate were frequently followed by further dipping. Postcopulatory dipping may represent attempts by the male to initiate oviposition. After about 13:30 h, little or no reproductive activity was seen and both sexes joined in the immense feeding swarms which built up over the rice fields until dusk. Intense competition for females may explain the prolonged phase of pre-copulatory guarding (tandem formation) in a species in which both sexes remain abundant at or near the oviposition sites throughout the day. but in which females are willing to oviposit only during the later part of the morning.