Reproductive behavior of two Argia spp. (Odonata: Coenagrionidae) at an Arizona stream

Abstract

Here we provide a first report on the reproductive behavior of Argia sabino Garrison and Argia pima Garrison from observations at Sabino Creek, Arizona. Both species reproduce in autumn (September-October) following late summer rainstorms. Tandem pairs of A. sabino submerge to oviposit on rock substrates. The oviposition substrate is abundant and widespread. Male A. sabino defend mate-encounter territories in the morning at boulder fields or rock outcrops away from the stream. Copulation may last 30 minutes or more. Ovipositing females submerge in tandem with males, typically to depths of 10-30 cm, and pairs may remain submerged for over 30 minutes. Male submergence with females can be interpreted as contact mate guarding promoted by sperm competition and/or as a male investment in the female’s survival and oviposition success. We discuss evidence for both possibilities based on field observations. Whereas ovipositional resources for A. sabino are ubiquitous at Sabino Creek, A. pima uses patchily distributed, discrete ovipositional habitats (wetted rootlets of riparian trees at waterfalls and riffles). Males of A. pima employ a mixture of contact and noncontact mate-attendance strategies. Females occasionally submerge to oviposit. Often they oviposit along the margins of torrential cascades. Male A. pima have been observed to release submerging mates just before their own wings become wetted, and to monitor submerged ovipositing females from a nearby perch thereafter.

Keywords: Argia, Odonata, dragonfly, reproduction, North America

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