Physiological benefits of nectar feeding by a predatory beetle

Abstract

Extrafloral nectar is an important food source for many animals, including predatory lady beetles (Coleoptera: Coccinellidae), although the physiological benefits of nectar consumption are poorly understood for most consumers. Under laboratory conditions, we confined new females of Coleomegilla maculata, a North American lady beetle, to Vicia faba plants with or without extrafloral nectaries for 10 days; after this, the beetles were moved onto a high-quality diet for an additional 15 days. Survival, fecundity, and oocyte size and development before and after consuming a high-quality diet were compared between treatments. Colorimetric assays were used to quantify the glycogen and lipid reserves of the beetles before and after exposure to a high-quality diet. Extrafloral nectar increased the survival of C. maculata by 50%, and increased fecundity by 30%, over starved individuals. Oocytes prior to and following exposure to a high-quality diet were significantly larger in females fed nectar than in females that were not fed nectar. Finally, glycogen reserves were higher following the prey-free period in the nectar-fed treatment than the starved treatment, but this deficiency did not persist once a high-quality diet was provided. We conclude that nectar improves the survival and nutrient reserves of predators during periods of prey scarcity, and that the availability of nectar during these periods improves the long-term reproductive capacity of predators.

Herbivores, saprovores and natural enemies respond differently to within-field plant characteristics of wheat fields

“…We also observed a positive correlation between the number of predators and legume cover. This supports existing evidence that consuming flowers and extrafloral nectaries improves the survival and nutrient reserves of predators during periods of prey scarcity, and that the availability of nectar during these periods improves the long-term reproductive capacity of predators (Hodek and Honek 1996;Norris and Kogan 2000;Isaacs et al 2009;Lundgren and Seagraves 2011;Amaral et al 2013).…”

Effects of floral and extrafloral resource diversity on the fitness of an omnivorous bug, Orius insidiosus

“…In contrast, covering the pollen and nectar sources did not produce different levels of glycogen or lipids in the bugs. Other recent work, however, has shown that while access to nectar greatly improved the levels of glycogen in a predatory beetle, the lipid contents were similar when they were compared with no access to nectar (Lundgren & Seagraves, ). Access to sugar sources also increased the glycogen levels, but not the lipids on a female parasitoid species when it was compared with starved insects (Olson et al., ).…”

“…On the contrary, females on the covered treatments, lacking these nutritional resources may have had more incentive to find or create escape routes from the arena (no corpses were found of the missing individuals, reducing the likelihood of cannibalism in the covered treatment). In many other studies, access to sugar sources has improved the survival of predators (Lundgren & Seagraves, ; Portillo et al., ) and parasitoids (Olson et al., ; Lee et al., ). We found that O. insidiosus females laid more eggs when offered nectar and pollen than when these resources were restricted on three of the four flowering plants, although the greatest benefit of floral resources was observed in chamomile, which had low levels of aphids near the flowers.…”

“…As a result, the provision of flowering plants can enhance the effectiveness of natural enemies by increasing their longevity, fecundity, and predation or parasitism rates (Berndt & Wratten, ; Begum et al., ; Lee & Heimpel, ). Specifically, sugar feeding improves the fitness and performance, and affects the nutrient status in parasitoids (Olson et al., ; Lee et al., ; Chen & Fadamiro, ; Nafziger & Fadamiro, ) and predators (Lundgren & Seagraves, ; Seagraves et al., ). Research has long supported the importance of nectar feeding for parasitoid life histories, but nectar resources for predators have received less attention until recently.…”

“…Although plants are known to be important food sources for predators, the physiological benefits and metabolic uses of the different plant subsidies are still poorly understood. Some authors have observed that restricting the access of predators to nectar can reduce their survival and fitness considerably (Lundgren & Seagraves, ; Portillo et al., ).…”