Consumption of nectar-like sugar solutions promotes longevity and fecundity in the ladybird beetles Harmonia axyridis and Hippodamia convergens

Abstract

Coccinellids (Coccinellidae, commonly referred to as ladybeetles, ladybugs, or ladybirds) are predatory insects that often contribute to the biological control of crop pests. Especially when prey is limited, ladybirds have been reported to consume plant resources such as nectar. However, the importance of nectar consumption to ladybird fitness is not well understood. We performed artificial feeder experiments confirming ladybird consumption of a sugar solution with carbohydrate ratios similar to nectar. Both Harmonia axyridis (harlequin ladybird) and Hippodamia convergens (convergent ladybird) depleted sugar solution in 100% of trials. We also tested the effects of aphid and sugar solution availability on longevity and fecundity of these species. Ladybirds generally died within 10 days if no food was provided but survived for 10 days when either aphids or sugar solution were available. Aphids were required for oviposition. However, when aphids were available, oviposition was 36–90% higher when sugar solution was available as well. We conclude that nectar availability has significant potential to increase ladybird fitness, so may be worth considering in the design of conservation biological control programs.