Geographic origin of a factitious host shapes parasitoid performance in Trichogramma chilonis–Antheraea pernyi systems

Geographical variation can profoundly influence host-parasitoid compatibility and mass-rearing performance in biological control programs. We assessed how the geographical origin of the Chinese oak silkworm (Antheraea pernyi) affects the reproductive performance of the egg parasitoid Trichogramma chilonis. Two A. pernyi populations from Jilin (JCOS) and Guizhou (GCOS) provinces, and two T. chilonis populations from the same regions (JL-TC and GZ-TC), were reciprocally tested to evaluate host suitability. Morphometric analyses revealed that JCOS exhibited a larger body size, a longer wingspan, and thicker eggshells than GCOS, indicating regional morphological differentiation. Parasitism and emergence rates were significantly higher on GCOS eggs (82–86% and 67–76%, respectively) than on JCOS eggs (70–75% and 41–47%), primarily because their thinner eggshells facilitated oviposition and adult emergence. Development duration was shorter on GCOS eggs, while the proportion of female progeny remained consistently high (> 85%) across treatments. Although T. chilonis populations showed comparable parasitism levels, the JL-TC strain produced slightly more female offspring than GZ-TC, suggesting minor adaptive divergence. Regression analyses demonstrated a strong negative correlation between eggshell thickness and parasitoid emergence, confirming eggshell structure as a critical determinant of host suitability. These findings highlight that the geographical origin and morphological traits of A. pernyi influence the reproductive success of T. chilonis. Selecting optimal host populations, such as GCOS, can enhance parasitoid production efficiency and reliability, improving the sustainability of mass-rearing systems and biological control programs.