Biology and Demographic Parameters of Rhyzobius lophanthae (Coleoptera: Coccinellidae) on Armored Scale Insects

Abstract

Rhyzobius lophanthae Blaisdell (Coleoptera: Coccinellidae) is a specialist predatory beetle of considerable biocontrol significance, widely recognized for its predatory efficacy against armored scale insects (Hemiptera: Diaspididae), which constitute a globally distributed and economically damaging pest complex infesting fruit trees, ornamental plants, and various perennial crops. Despite the established deployment of R. lophanthae in augmentative and classical biological control programs, a rigorous quantitative characterization of its developmental biology, reproductive performance, and demographic parameters across biologically relevant prey species and environmental conditions remains essential for optimizing mass-rearing efficiency and accurately predicting field suppression capacity against target diaspidid populations. This study investigated the biology and demographic parameters of R. lophanthae reared on armored scale insect prey under controlled laboratory conditions with standardized temperature, photoperiod, and relative humidity regimes. Duration of egg, larval instar, pupal, and adult developmental stages were recorded and analyzed alongside adult longevity, preoviposition period, oviposition rate, and total fecundity across the reproductive lifespan of female cohorts. Age-specific survival and fecundity data were incorporated into the age-stage, two-sex life table analytical framework to calculate key demographic indices including the net reproductive rate, intrinsic rate of natural increase, finite rate of increase, mean generation time, and population doubling time. Predation capacity of larval instars and adults was quantified through functional response experiments across a range of prey densities to assess foraging efficiency. Significant variation in developmental rate and reproductive output was detected in relation to prey species identity, highlighting the influence of prey nutritional quality on predator fitness parameters. These findings provide a comprehensive biological and demographic reference essential for mass-rearing program optimization, release rate determination, and the integration of R. lophanthae into evidence-based biological control strategies targeting armored scale insects in perennial crop production systems.