Bacterial Communities Associated with Whole Eggs and Gut Tissues of Heortia vitessoides Moore (Lepidoptera: Crambidae) Across Developmental Stages and Sexes

Bacterial communities may affect insect nutrition and development, but their variation across complete metamorphosis remains poorly understood in many forest lepidopteran pests. Heortia vitessoides is an important defoliator of Aquilaria trees, which produce agarwood. In this study, we used 16S rRNA gene sequencing to characterize bacteria associated with whole eggs and gut tissues from larvae, pupae, and adults of H. vitessoides. Whole egg and larval gut samples generally showed higher bacterial richness and diversity than pupal and adult gut samples. Bacterial community composition differed among the six groups examined, including whole eggs, larval guts, male pupal guts, female pupal guts, male adult guts, and female adult guts; a separate analysis of gut samples also indicated differences among larval, pupal, and adult gut communities. Proteobacteria, especially Acinetobacter, were abundant in whole egg and larval gut samples, whereas adult gut samples were dominated by Firmicutes, particularly Enterococcus. Sex-related differences were mainly observed in pupae, with Methylobacterium and Pseudomonas showing higher relative abundances in female pupae. PICRUSt2 predicted functional categories mainly related to nutrient metabolism and membrane transport. In a preliminary egg surface sterilization assay, larvae from treated eggs showed longer larval and total developmental durations than controls. Overall, these results provide baseline information on bacteria associated with whole eggs and gut tissues of H. vitessoides and identify candidate taxa for future functional studies.