Abstract The egg parasitoid Mesocomys trabalae Yao, Yang, and Zhao is used as a biocontrol agent against the emerging defoliator pest Caligula japonica Moore in East Asia. It has been proven that the eggs of Antheraea pernyi Guérin-Méneville can be used as a factitious host for the mass production of M. trabalae. We examined the parasitic behavior and morphological characteristics of the developmental stages of M. trabalae reared on A. pernyi eggs. The parasitic behavior of M. trabalae encompasses 10 steps, involving searching, antennation, locating the oviposition site, drilling, probing, detecting, oviposition, host feeding, grooming, and resting, with the oviposition step further divided into 3 stages. We determined that the parasitoid released an egg during the second stage of the oviposition step, while her body remained in a relatively static state. Among all the steps in parasitic behavior, probing occupied the longest time, accounting for 26.33% of the entire parasitism process. It was followed by oviposition (15.88%), drilling (15.10%), antennation (13.09%), detecting (10.79%), host feeding (10.02%), and the remaining steps, each occupying less than 5.00% of the total time in steps. The pre-emergence of adult M. trabalae comprised of 4 stages: egg (0–1 day), larva (2–6 days), prepupa (7–11 days), pupa (12–20 days), followed by the development into an adult, and it usually took 20–22 days to develop from an egg into an adult at 25°C. This study advances our understanding of the biology of Mesocomys parasitoids and their mass-rearing for use in augmentation programs.