<div>Background: The coconut black-headed caterpillar, Opisina arenosella Walker (Lepidoptera: Xyloryctidae) has been a serious defoliator of coconut plants in many coconut producing countries including Vietnam. Trichospilus pupivorus Ferri&egrave;re (Hymenoptera: Eulophidae) is pupal endo-parasitoid of O. arenosella with high percent parasitism and abundance in the coconut fields and appears to be a good biological control agent against the coconut black-headed caterpillar in Vietnam. The objective of this study was to investigate the developmental biology of T. pupivorus on O. arenosella. 
 
Methods: The experiment was carried out at the Faculty of Agronomy, Nong Lam University, Viet Nam during 2020 and 2021. The developmental biology of T. pupivorus on O. arenosella was studied in the laboratory at a constant temperature of 28&deg;C and a photoperiod of 12L: 8D.&nbsp; 
 
Result: Total developmental time from egg to adult emergence was 14.0 days. The females laid a mean of 124.2 eggs during an average lifespan of 9.4 days. The number of progenies emergence from a single pupa of O. arenosella was 103.8. The offspring sex ratio was female-biased (8.0%). The results would contribute to the knowledge of the biology of this parasitoid to optimize a mass rearing system for a biological control program against O. arenosella.</div>

Developmental Biology of Trichospilus pupivorus Ferri&egrave;re (Hymenoptera: Eulophidae), a Pupal Parasitoid of the Coconut Black-headed Caterpillar, Opisina arenosella Walker (Lepidoptera: Xyloryctidae)