Transmission of the internal microbiota of cotton field-collected bollworms (Lepidoptera: Noctuidae), from larvae to pupae and adults

Caterpillar pests and their microbiota are of growing interest in relation to pest control, including any future use of living wild-type or genetically modified microbes for pest suppression and risk assessment. This study investigated whether bacteria associated with field-collected larval bollworms, Helicoverpa zea, persist through metamorphosis to the adult, potentially enabling the insects to transport microbes over long distances as the moths disperse. Fifth stadium, fully fed larvae were collected from non-Bt cotton in the field and allowed to pupate without additional feeding and emerge as adults in the laboratory. Bacterial community composition and diversity were assessed at each stage using Illumina sequencing of the 16S rRNA gene. Analysis of the internal bacterial communities revealed that alpha and beta diversity differed significantly between larvae, pupae, and adults. Despite this difference, 79 amplicon sequence variants were retained from the larval to the adult stage. The 5 most abundant taxa shared between larvae, pupae, and adults were Enterobacter, Klebsiella, an undefined Enterobacteriaceae species, Enterococcus casseliflavus, and Klebsiella oxytoca. Some of these bacteria are typical gut microbes. Further research is needed to characterize the composition and functional roles of these bacteria in H. zea, to evaluate their influence across generations, and to determine whether bacteria can be acquired by the larvae from their environment and persist into the adult stage. The role of the caterpillar microbiome in the context of modern cotton agroecosystems remains a largely understudied area of insect-microbe ecology.