High Variability in Pre-Oviposition Time Independent of Diet Available at Eclosion: A key Reproductive Trait in the Ladybird Beetle Harmonia axyridis (Coleoptera: Coccinellidae) in Its Native Range

Simple Summary Insect predators need high-quality food to reach sexual maturity and reproduce. Nonetheless, just emerged adults may face starvation when prey are missing, notably in agroecosystems. This study conducted in laboratory conditions explores whether the type of diet (flower food, prey food or no food) available just after adult eclosion is of critical importance for the future fecundity of adult ladybird beetles. Diet readily available just after emergence did not affect the fecundity and egg viability of Harmonia axyridis. Time from eclosion to first egg laying (called pre-oviposition time) of H. axyridis was highly variable and negatively related to fecundity and egg viability. This study clarifies that the food readily available at adult eclosion does not affect the capacity of H. axyridis to reproduce, provided that adults find prey within a few days. It is concluded that the reproductive strategy of H. axyridis allows this ladybird beetle species to be highly adapted to heterogenous environments in its native range, highlighting the importance of diversifying agroecosystems to enhance biological regulation of pests. While insect predators need high-quality food to reach sexual maturity and reproduce, starvation following adult eclosion may occur when prey are missing in agroecosystems. This study explores whether the type of diet available at eclosion determines the future fecundity of newly emerged adult predators. In a laboratory experiment, three different diets (i.e., flowers of Perilla frutescens (L.) Britton, eggs of Ephestia kuehniella Zeller as prey, or no food) were offered to adult females of the ladybird beetle Harmonia axyridis Pallas during their first three days after adult eclosion. On the fourth day, each female was paired with a prey-fed male and the pair was subsequently fed with prey. Diet at eclosion did not affect pre-oviposition time, the number of eggs oviposited daily, or the viability of egg batches. High variability in pre-oviposition time among females was observed for all diets. Significant negative linear relationships were found between pre-oviposition time and both the number of eggs oviposited daily and the viability of egg batches. This study clarifies that the food readily available at adult eclosion does not affect the capacity of H. axyridis to reproduce, provided that adults find prey within a few days. More generally, it shows that the reproductive traits of H. axyridis allow this generalist predator to be highly adapted to heterogenous environments in its native range. It is concluded that the variety of habitats offered by diversified agroecosystems may highly benefit the ladybird beetle H. axyridis, and potentially enhance its ability to biologically regulate crop pests.

Automated summary

The type of diet readily available after adult eclosion does not significantly affect the future fecundity of adult ladybird beetles, as long as they find prey within a few days. High variability in pre-oviposition time was observed among females, and significant negative relationships were found between pre-oviposition time and both the number of eggs oviposited daily and the viability of egg batches.