Sexual behaviour of the green capsid bug

The green capsid bug ( Lygocoris pabulinus (L.), Heteroptera; Miridae) is an unpredictable pest in fruit orchards in North-Western Europe, since it migrates twice a year. An efficient monitoring system to predict bug damage in an orchard may reduce the use of insectices. Such a monitoring system may be developed by exploiting the sex pheromone, as L. pabulinus males are attracted by virgin females. However, attempts to identify the pheromone in the past decade have failed, which may be due to a lack of understanding of their sexual behaviour as a whole. Therefore, the sexual behaviour of the green capsid bug was studied in detail. Males and females are sexually mature 4-5 days after the final moult. EAG-responses suggest that males are more sensitive to insect-produced pheromone-type compounds, whereas females are more sensitive to plant compounds. This correlates with their behaviour, as males are attracted to virgin and mated females at long range, with and without plants. The attraction is mediated by a sex pheromone, not an aggregation pheromone, since males are not attracted to males, and females are not attracted to either sex. Sex pheromone emission is inhibited by hexyl butanoate, the alarm pheromone of L. pabulinus. Females do not show a specific calling behaviour. At close range, males are attracted to female-specific, low volatile compounds, present on female legs. These compounds are also deposited on the substrate on which females walk. At long and close range, males vibrate with their abdomen when they perceive signals from females. Matings last only 1-2 minutes, during which a compartmentalized spermatophore is formed in the spermatheca of the female. A mating plug is part of the spermatophore, inducing a refractory period in females for about 24 hours. After 24 hours, sperm is released from the spermatophore and found throughout the spermatheca and the lateral oviduct. When males have mated, they do not respond to females for at least two hours. Multiply-mated females oviposit as many eggs and live as long as once-mated females. Virgin females also oviposit eggs, but these eggs do not hatch. Under summer conditions, females oviposit preferably in potato plants. This study shows that long-range mate location by means of a sex pheromone is only part of the sexual behaviour of the green capsid bug. For pest management, the alarm pheromone of L. pabulinus may be exploited to prevent bug damage in fruit orchards.