Field investigation of mating behaviour of Agrilus cyanescens and Agrilus subcinctus

We examined mate-finding behaviour in Agrilus subcinctus Gory (Coleoptera: Buprestidae) and Agrilus cyanescens Ratzeburg (Coleoptera: Buprestidae) in ash (Fraxinus L. (Oleaceae)) stands in the Great Lakes region of the United States of America. Dead specimens of both species were affixed to ash foliage to serve as models to test visual stimulation of aerial attraction of males. The models were washed in dichloromethane to remove cuticular lipids or were left unwashed, to test for the presence of close-range pheromonal cues. Males of both species located females via a visually guided aerial approach from up to 1 m above females, similar to the behaviour of Agrilus planipennis Fairmaire. When male A. subcinctus or A. cyanescens made contact with females, contact sex pheromones mediated subsequent copulation behaviour. During their visually mediated airborne descent and landing, male A. cyanescens landed directly on female models; whereas, male A. subcinctus landed significantly more often on the leaf surface supporting a model. Male A. subcintus performed precopulatory pounce behaviour on female models after assessing surface chemical cues with their antennae. Male A. cyanescens landed upon a variety of models, but after landing, rejected a significant proportion of models lacking female A. cyanescens cuticular lipids.