Population phenology of whitefringed weevil, Graphognathus leucoloma (Coleoptera: Curculionidae), in pasture in a Mediterranean-climate region of Australia

Abstract

AbstractIn undisturbed annual pasture in a Mediterranean-climate region of Australia adults of the whitefringed weevil, Graphognathus leucoloma (Boheman), were present from summer to early winter (December–June), with upsurge in numbers of first instar larvae only occurring after the rains began in April. The G. leucoloma population was predominantly first instar larvae in high abundance throughout the winter period (May–August). Larval growth, with high mortality, occurred in the spring period (September–January). The survival of eggs during the dry summer when adults were most abundant, although only at times of unseasonal rainfall, indicated that low larval recruitment at that time resulted primarily from the absence of high-quality legume food essential for oogenesis. It was inferred that most larvae arose from heavy oviposition by the few adults present in autumn when rainfall germinated annual legumes. A steady year-round abundance of late-instar larvae indicated that not all individuals completed their development in the one year.