Plant resources mediate reproduction, flight, and body condition in a specialized aphid predator, Hippodamia convergens (Coleoptera: Coccinellidae)

Adult aphid predators disperse across the landscape seasonally in search of patchily distributed and temporally available prey aggregations. However, flight is energetically costly and consumes resources that could be subsequently invested in reproduction. Hippodamia convergens is an important aphid predator that utilizes floral resources to increase its fitness and improve survival during periods of prey scarcity via body size, fecundity, and dispersal. We tested how adult consumption of floral resources interacts with body size to influence reproduction, flight behavior, and physiological condition. Two beetle sizes were produced by manipulating larval access to food – 3h daily access produced small beetles; ad libitum access produced large beetles. We tracked same-sized adult pairs’ reproduction for 18 days, and female flight was assayed via 3h tethered flight bouts. Physiological condition was sampled throughout the experiment to assess how macronutrient ratios in body composition fluctuate in response to flight and reproduction. Beetles fed ad libitum developed faster and grew larger than beetles on restricted diets. Omnivorous adults showed higher fecundity than prey-only diets; but egg fertility was unaffected. Adult size affected fecundity only slightly, but significantly altered oviposition patterns, with smaller beetles laying smaller, but more numerous clutches. Diet and size interacted to influence preoviposition period with larger prey-only treatments delaying oviposition the longest. Size and reproduction marginally influenced flight behavior in adult beetles only interactively. Thus, supplementary dietary plant resources can increase reproductive success and alter oviposition patterns in H. convergens, but effects on flight and physiology varied among adult sizes and diet.