Structure and biomechanics of the antennal grooming mechanism in the southern green stink bug Nezara viridula

Abstract

Insects devote a large amount of time to self-groom to remove foreign material, especially from their sensory appendages. Using various microscopy techniques and behavioural experiments on intact and ablated insects, the present study investigates the antennal grooming of the southern green stinkbug Nezara viridula, which represents a serious pest of different crops in most areas of the world. The antennal grooming behaviour encompasses an action of scraping involving the tibial comb complex (tibial comb + fossula) of both forelegs, generally followed by the tibial comb complex grooming of one leg using the tarsal hairy adhesive pad of the opposite leg (rubbing). From our observations, we can exclude a role in the antennal grooming of other structures such as the foretibial apparatus, while we show an involvement of this last structure in repositioning the stylets inside the labium. The external and internal morphology (cryo-scanning and transmission electron microscopy) and the evidence for the presence of large proportions of the elastic protein resilin (confocal laser scanning microscopy) in some parts of both the tibial comb complex and the foretibial apparatus are shown, and their functional roles are discussed. For the first time we demonstrated here the multipurpose role of the basitarsal hairy adhesive pad that is involved in both antennal grooming and adhesion to the substrate.