The Benefits of Omnivory for Reproduction and Life History of a Specialized Aphid Predator,Hippodamia convergens(Coleoptera: Coccinellidae)

Abstract

The convergent lady beetle, Hippodamia convergens Guerin-Meneville, is a specialized predator of cereal aphids on the High Plains, completing its first generation each year in winter wheat, the resulting adults dispersing into summer crops and producing additional generations, contingent on the availability of aphids. In the present study, we tested the collective value of supplementary plant resources (sugars, pollen, and seedling wheat leaves), and small amounts of alternative prey, eggs of Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae), all provided together, for improving beetle life history and reproductive success even when suitable prey, Schizaphis graminum (Rondani) (Hemiptera: Aphididae), were provided ad libitum. Although a monotypic diet of S. graminum yielded slightly faster larval development and heavier adults than the omnivorous diet, preoviposition periods were extended and 21-d fecundities greatly reduced when this diet was continued through adult life, largely due to fewer oviposition days, although egg fertility was unaffected. The results highlight the critical importance of plant-derived resources even when suitable prey are not limiting. However, monotypic diet beetles that diapaused for 21 d in the presence of supplementary plant resources, plus moth eggs, achieved the same reproductive success as those reared on the omnivorous diet, with or without diapause, demonstrating that access to these resources post-emergence was sufficient to compensate for their absence during development. The diapause treatment itself had no impact on the fitness of beetles reared on the omnivorous diet, likely because neither its duration, nor the caloric restriction imposed, were sufficient to diminish reproductive effort.

Effect of Sinapis alba L. as an Insectary Plant on the Occurrence of Aphis fabae Scop., Coccinellidae and Syrphidae in Broad Bean

“…This fact may be explained by an easier access to food sources (flower pollen and aphids) with lower plant density. Although for lady beetles the main attractant is the presence of aphids, the supplementary plant resources (such as pollen) may be of key significance for reproduction and life history even when suitable prey are not limiting [42]. In our experiment there was no significant effect of thinning on aphids abundance.…”

Floral Resources Enhance Fecundity, but Not Flight Activity, in a Specialized Aphid Predator, Hippodamia convergens (Coleoptera: Coccinellidae)

“…The omnivorous adult diet resulted in greater female fecundity than did the prey-only diet, supporting our initial hypothesis, and confirming that floral resources complement the nutrition provided by prey, and are essential to maximal reproductive success in this species. Previous studies have similarly concluded that plant-derived foods generally enhance the performance of predatory coccinellids relative to prey-only diets (Lundgren, 2009), including H. convergens (Stowe et al, 2021). Supplemental (plant-derived) foods have long been recognized for their importance to coccinellid survival during periods of prey scarcity (Hodek, 1996;Michaud and Qureshi, 2005), but may also provide phytosterols, key requirements for development and reproduction that insects are unable to synthesize endogenously (Levinson, 1962;Behmer and Nes, 2003;Pilorget et al, 2010).…”

“…Supplemental foods of plant origin not only support the survival of predaceous coccinellids in the absence of animal prey (Hodek, 1996;Hatt and Osawa, 2019) they are often necessary for the beetles to achieve maximal fitness (Lundgren, 2009;Michaud, 2018;Stowe et al, 2021). Consequently, these resources are also consumed during periods of prey abundance (Berkvens et al, 2010;Hodek and Evans, 2012;Choate and Lundgren, 2013;Ugine et al, 2019), and may be selectively consumed when particular nutrients are lacking in the diet (Schuldiner-Harpaz and Coll, 2017).…”

Resource amount and discontinuity influence flight and reproduction in Hippodamia convergens (Coleoptera: Coccinellidae)

“…This result could reflect reduced egg or sperm viability due to nutrient limitation. Although differences in food quantity or quality do not always affect egg fertility in H. convergens (e.g., Stowe et al, 2021;Vargas et al, 2012a), effects can appear over longer observational periods, as egg fertility declines as a function of maternal age in both very large and very small females, and eggs get progressively smaller with age in the case of the latter (Vargas et al, 2012a(Vargas et al, , 2012b. Any reduction in egg fertility may also improve the survival of siblings, given that cannibalism of infertile eggs within hatching clusters provides a valuable food source for eclosing larvae within hatching clusters (Michaud & Grant, 2004;Osawa, 1992).…”