# Effects of Corcyra cephalonica Egg Consumption on Population Fitness and Reproduction of the Whitefly Predator Serangium japonicum (Coleoptera: Coccinellidae)

## TL;DR

Feeding a ladybird beetle an alternative diet of rice moth eggs extends its lifespan but reduces its reproductive ability, which is important for mass production in pest control.

## Contribution

Identifies the physiological and molecular mechanisms behind the reproduction-lifespan trade-off in S. japonicum when fed Corcyra cephalonica eggs.

## Key findings

- Feeding on C. cephalonica eggs extends the lifespan of S. japonicum without affecting offspring quality.
- The alternative diet impairs reproduction by delaying ovarian development and altering key gene expressions.
- C. cephalonica eggs are a viable supplementary diet but unsuitable as a sole diet for mass-rearing.

## Abstract

Ladybird beetle, Serangium japonicum, is an effective natural enemy of whiteflies in China. Serangium japonicum has shown promising results in field, but its mass-production needs a suitable and affordable artificial diet. This study investigates the feasibility of using rice moth (Corcyra cephalonica) as an alternative food source for S. japonicum adults. We found that while this diet allowed the beetles to develop normally with longer life periods, it significantly reduced their ability to reproduce by delaying ovary development as well as affecting the activity of key reproduction related genes. Our findings explain the trade-off between a longer life period and lower reproduction when feeding on this alternative diet. These findings provide crucial information for optimizing the mass production of this natural enemy for effective and sustainable pest control.

Ladybird beetle, Serangium japonicum (Coleoptera: Coccinellidae), is an important predatory natural enemy of whiteflies, and its mass rearing is crucial for biological control. This study evaluated the suitability of Corcyra cephalonica (Lepidoptera: Pyralidae) eggs as an alternative diet for adult S. japonicum by directly comparing it to the natural prey, Bemisia tabaci (Hemiptera: Aleyrodidae) nymphs. Results showed that, compared to a B. tabaci diet, feeding on C. cephalonica eggs supported normal development and significantly extended the lifespan of adult S. japonicum, without compromising offspring quality (hatching rate, development, survival, or predatory capacity). However, the moth egg diet significantly impaired reproduction, causing delayed ovarian development, reduced vitellogenesis, and altered gene expression: downregulation of methoprene-tolerant, Juvenile hormone acid O-methyltransferase, Vitellogenin, and Vitellogenin receptor, and upregulation of Juvenile hormone esterase and Copper/zinc superoxide dismutase. Practically, this work defines C. cephalonica eggs as a suboptimal but viable supplementary diet for colony maintenance, but unsuitable as a sole diet for mass-rearing reproductively robust populations. Our findings explain the physiological and molecular mechanisms underlying the “reproduction–lifespan trade-off” in S. japonicum induced by feeding on C. cephalonica eggs, providing a mechanistic basis for its rational application in the mass production of natural enemies.