# Parasitic Recognition Behavior of Telenomus remus Nixon, an Important Egg Parasitoid of Spodoptera frugiperda (J. E. Smith)

## TL;DR

This paper studies how Telenomus remus, a parasitic wasp, identifies and avoids re-parasitizing eggs of the fall armyworm, offering insights for biological control strategies.

## Contribution

The study reveals how T. remus uses experience and environmental cues to avoid superparasitism, enhancing biological control applications.

## Key findings

- T. remus performs a distinctive '8'-shaped marking to deter conspecifics from parasitizing the same host.
- Experienced females can recognize marked eggs across a wide temperature range and time intervals.
- Parasitism rates increase with host density, and searching time decreases.

## Abstract

The fall armyworm, Spodoptera frugiperda, is a major pest of maize. Since its invasion of China in 2019, it has rapidly established itself and spread to most regions of the country. Its polyphagous feeding habits, high feeding capacity, rapid development cycle, robust reproductive potential, resistance to pesticides, and migratory tendencies pose significant challenges for its control. Utilizing natural enemies for biological control is therefore an essential strategy. The parasitoid, Telenomus remus, serves as an important egg parasitoid targeting various lepidopteran pests, and has demonstrated substantial efficacy against S. frugiperda. This study examined the host discrimination and marking behavior of T. remus, specifically assessing its ability to identify host eggs marked by itself or conspecific individuals under different temperature conditions and oviposition intervals. The results contribute to a deeper understanding of the parasitic behavioral traits of T. remus and offer an essential scientific foundation for its mass rearing and application in biological control programs.

T. remus is an important egg parasitoid of S. frugiperda, serving as a significant role in its biological control. This study systematically examined the host discrimination behavior of T. remus. The parasitic process comprises several distinct behavioral stages: host searching, antennal tapping and examination, ovipositor probing, “8”-shaped marking, and grooming. Following successful oviposition, females perform a characteristic “8”-shaped marking on the host egg surface with their ovipositor, which deters conspecific females from parasitizing the same host. T. remus exhibited a pronounced ability to discriminate parasitized hosts, utilizing both antennae and ovipositor to avoid superparasitism. As host density increased, the searching time of T. remus decreased while the parasitism rate increased, eventually stabilizing. Parasitic discrimination was significantly influenced by oviposition experience: experienced females effectively recognized marked host eggs across a temperature range of 16 to 36 °C and time intervals of 0 to 12 h post oviposition. In contrast, naive females exhibited discrimination ability only at lower temperature (16 °C) and immediately following oviposition (0 h). These findings deepen the understanding of the behavioral ecology of T. remus and provide a crucial theoretical basis for its efficient application in the biological control of S. frugiperda.