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

Abstract

Adult aphid predators disperse across the landscape seasonally in search of prey aggregations that are patchily distributed and temporally variable. However, flight is energetically costly and consumes resources that could be invested in reproduction. Hippodamia convergens is an important aphid predator in North American cereal crops and other agricultural systems. Consumption of floral resources can enhance adult survival during periods of low prey availability and may improve reproductive success. We tested how an omnivorous adult diet containing floral resources (diluted honey and pulverized bee pollen) interacts with body size to influence reproduction and flight behavior compared to a prey-only diet. Two sizes of beetles were produced by controlling larval access to food—3 h daily access produced small beetles; ad libitum access produced large beetles with faster development. Reproductive performance was tracked for 18 days, and female flight activity was assayed via 3 h bouts of tethered flight. Diet composition and body size interacted to influence preoviposition period, with large females in prey-only treatments delaying oviposition the longest. The omnivorous adult diet improved 18-day fecundity relative to a prey-only diet, but egg fertility was unaffected. Adult size affected oviposition pattern, with small beetles laying smaller, but more numerous, clutches. Females flew up to 7 km in 6 h, but neither body size nor adult diet influenced flight distance, suggesting that all diet treatments generated energy reserves sufficient to power flights of short duration. However, pre-reproductive females flew > 60% further than they did post-reproduction, likely due to the energetic costs of oviposition. Thus, access to pollen and nectar increased reproductive success and altered oviposition patterns in H. convergens, indicating the importance of floral resources in the agricultural landscape to conservation of this predator and its biological control services.

Response of the Coccinellidae Community within Sustainable Vineyards to the Surrounding Landscape

“…These species are common in other Portuguese crops, such as chestnut, almond, or olive groves [31,43,72]. Scymnus apetzi and S. interruptus were also frequent species in Portuguese citrus groves [45], preying mainly on aphids [27,39,41]. Their high abundance in olive and citrus groves suggested that they probably feed on the black scale, S. oleae, a frequent coccid pest in both crops, as well as other coccids and pseudococcids [31,44].…”

“…This tribe is mainly composed by predators of aphids [74], psyllids, and Chrysomelidae [27]. It includes C. septempunctata, the third more abundant species in the study, which besides aphids [39], feed on pollen [27]. In Portugal, this species is frequent in chestnuts [43], citrus groves [45], and almond trees [42].…”

“…Coccinellidae are widely known for their predatory feeding habits [35], but can supplement their most common diet with non-prey supplementary foods, such as pollen, nectar, or insect honeydew [36], and even rely on them when food is scarce [29,37]. Moreover, both preys and supplementary foods (e.g., flowers) occur seasonally and patchily across the landscape where predators disperse, searching for food [38,39]. The effect of the landscape on Coccinellidae within vineyards was demonstrated in some cases.…”

Agriculturally Intensified Landscapes Are Associated With Reduced Body Condition of Lady Beetles

“…Corn and soybean fields can be heavily colonized by aphids and thus provide abundant prey for lady beetles, but this is only the case during limited time periods; over long periods such fields are characterized by resource scarcity, e.g., before crop emergence, after crop maturity, or after pesticide application (Rand et al 2006;Schellhorn et al 2014;Iuliano and Gratton 2020). In landscapes that are strongly dominated by a few crop monocultures, these periods are synchronized over large areas and habitat patches with alternative food sources are often far away and only accessible at high energetic costs (Bonte et al 2012;Stowe et al 2021b).…”

Canola bee pollen is an effective artificial diet additive for improving larval development of predatory coccinellids: a lesson from Harmonia axyridis

“…The omnivorous behavior of predatory ladybird beetles is mainly driven by an appetite for nutrients, such as sterols found in the foliage 5–7 . Consequently, supplementary consumption of plant‐derived foods is therefore often necessary for the beetles to achieve maximal fitness 2,8,9 . For example, a significantly reduced preoviposition period and a substantial increase in 21‐day fecundities were observed in Hippodamia convergens Guérin‐Méneville (Coleoptera: Coccinellidae) when eating an omnivorous diet consisting of sugars, pollen, seedling wheat leaves, and eggs of Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) compared to feeding solely on the monotypic aphid prey, Schizaphis graminum (Rondani) (Hemiptera: Aphididae) 9 .…”