# Comparing the Developmental Biology and Brood Size of Four Sclerodermus Species (Hymenoptera: Bethylidae)

## TL;DR

This study compares the development and reproduction of four wasp species used to control forest pests in China.

## Contribution

The study reveals specific biological differences in developmental stages and offspring numbers among four Sclerodermus species.

## Key findings

- Sclerodermus alternatusi has fewer female offspring and more winged females compared to other species.
- Sclerodermus guani has the largest brood size and highest number of female offspring.
- All species showed similar survival rates after 120 days at 12°C.

## Abstract

Four species of Sclerodermus, which are important parasitoids of long-horned beetles in China, have been widely used to control forest trunk-boring pests for over 40 years. However, little is known about their developmental differences. This study aims to help determine the biological differences between the four wasp species and to improve the effectiveness of mass-rearing them for the biological control of forest pests. Sclerodermus alternatusi has a significantly larger number of F2 male offspring than the other three wasps and has a larger percentage of winged females. The brood size of Sclerodermus guani is largest.

Sclerodermus guani Xiao et Wu, Sclerodermus sichuanensis Xiao, Sclerodermus pupariae Yang et Yao, and Sclerodermus alternatusi Yang are four species of Sclerodermus that have been found in China on longhorn or buprestid beetle hosts. These parasitoids are of great importance to forest management because they control certain forest pests. Knowledge of their developmental differences is important for maximizing their use in bio-control programs, yet little about them is known. This study compared their number of offspring and developmental biology. There were significant differences in the four parasitoids’ egg, larval, pupal, and total developmental stages. The F2 male offspring of each parasitoid emerged approximately one day ahead of the female. Additionally, there were differences in the number of F2 male and female offspring, as well as in the sex percentage, among the four parasitoids. Compared to the other three wasps, S. alternatusi had a significantly lower F2 female percentage of 67.07%, which was notably less than that of the other wasps (over 90%). The total F2 offspring number and F2 female offspring number of S. guani were the greatest. Sclerodermus alteratusi produced a larger percentage of winged females (5.66%) compared to S. pupariae (3.98%), and no winged females developed from S. guani or S. sichuanensis. Almost all individuals survived the 30-day experiment, the survival rate decreased to about half after 120 days at 12 °C, and there was no difference between the species. The biological differences between the four wasp species analyzed in this study will help improve the effectiveness of mass-rearing them for the biological control of forest pests.