Cheilomenes sexmaculata (Coccinellidae: Coleoptera) as a potential biocontrol agent for aphids based on age-stage, two-sex life table

Chemotaxis response and age-stage, two-sex life table of the Cheilomenes sexmaculata (Fabricius) (Coccinellidae: Coleoptera) against different aphid species

The Cheilomenes sexmaculata (Fabricius) (Coleoptera: Coccinellidae), is one of the most beneficial and identifiable predators of numerous soft-bodied and sucking insect pests of several crops. Biological parameters and olfactory response of C. sexmaculata were investigated under laboratory conditions by providing three different aphid species i.e., mustard aphid (Lipaphis erysimi Kaltenbach), citrus black aphid (Toxoptera citricida Kirkaldy), and peach aphid (Diuraphis noxia Kurdjumov) as a food source. The developmental period of immature stages of C. sexmaculata was shorter on D. noxia as compared to other aphid species. The adult longevities were longer on D. noxia and T. citricida while shorter on L. erysimi. Female fecundity was highest on D. noxia while lowest on L. erysimi. Life table parameters i.e., intrinsic rate of increase (r), finite rate of increase (λ), net reproductive rate (Ro), and gross reproductive rate (GRR) were maximum on D. noxia while minimum on L. erysimi. The mean generation time C. sexmaculata was 20.90, 23.69, and 26.2 days on D. noxia, L. erysimi, T. and citricida, respectively. These findings were further confirmed from the olfactory experiment where D. noxia proved to be the most preferred prey. This study provides necessary information for mass-rearing of C. sexmaculata.

Larval and/or Adult Exposure to Intraguild Predator Harmonia axyridis Alters Reproductive Allocation Decisions and Offspring Growth in Menochilus sexmaculatus

Maternal effects can reduce offspring susceptibility to predators by altering resource allocation to young and reproducing larger offspring. While the perception of predation risk can vary according to a prey's life stage, it is unclear whether maternally experienced intraguild predation (IGP) risk during different life stages influences the maternal effects of predatory insects. We investigated the influence of exposure to intraguild predators (Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae)) during the larval and/or adult stages on reproductive decisions and offspring growth in Menochilus sexmaculatus (Fabricius). Independent of the life stage, when M. sexmaculatus females experienced IGP risk, their body weight and fecundity decreased, but the proportion of trophic eggs produced increased. However, egg mass, egg clutch number, and egg clutch size were not influenced by the treatment. Next, when offspring encountered H. axyridis, mothers experiencing IGP risk during the larval and/or adult stages could increase their offspring's weight. Moreover, offspring in IGP environments reached a similar size as those with no-IGP environments when mothers experienced IGP risk during the larval and/or adult stages. Overall, M. sexmaculatus larval and/or adult exposure to IGP risk had no influence on egg size, but increased offspring body size when faced with H. axyridis. Additionally, mothers experiencing IGP risk during different life stages showed increased production of trophic eggs. Because IGP is frequently observed on M. sexmaculatus and favours relatively larger individuals, different stages of M. sexmaculatus express threat-sensitively to IGP risk; inducing maternal effects can be an adaptive survival strategy to defend against H. axyridis.