Pollen Feeding and Fitness in Praying Mantids: The Vegetarian Side of a Tritrophic Predator

Abstract

Although the importance of omnivory in food webs has been established, the community niche of generalist arthropod predators such as praying mantids is usually assumed to be at most bitrophic, feeding on herbivores and other carnivores. As with most predators, mantids often are food limited in nature. Flowering plants in their environment offer mantids an opportunity to obtain high-protein pollen, a potential vegetarian alternative to their normal arthropod prey. Although some arthropod predators have been shown to feed occasionally on pollen, the extent to which they gain fitness from this behavior is unclear, and often assumed to be minor. In replicated laboratory tests, Chinese mantids, Tenodera aridifolia sinensis (Saussure), actively fed on pollen just after hatching, and on pollen-laden insects as adults. Pollen feeding enhanced fitness of these mantids by: 1) preventing starvation of nymphs at egg hatch in the absence of normal insect prey; 2) increasing body mass of nymphs fed pollen in addition to normal prey; and 3) allowing adults that were fed both pollen and insects to maintain the same fecundity on fewer insect prey than those fed insects alone. These predators are therefore tritrophic because the extent of their omnivory includes a fitness-enhancing plant product in addition to herbivore and carnivore prey. Pollen feeding may explain higher fecundity of females located on flowers, and also may enable these and other generalist predators to maintain high population densities when animal prey are scarce, which has potential consequences for the rest of the community.