Response of the green June beetle and its gut microbiome to RDX and phenanthrene

Green June beetles are a cosmopolitan pest in the United States. Adults are voracious consumers of tree and vine fruit, while their larvae can dam-age and inadvertently consume root systems, particularly those of grasses, as they move through the soil and forage for detritus. Larvae ingest and process large volumes of soil while in the process of feeding. Due to their intimate contact with the soil it was hypothesized that soil contaminants that are known animal toxins would perturb the larval and affect their overall health and survival. Studies of this kind are important contribu-tions to the development of new model organisms and our understanding of interactions between the environment, contaminants, gut microbiome, and animal development, health, and survival. It is important to continue to develop relevant model organisms for monitoring toxicity as regulations for working with vertebrates becomes more prohibitive. In this study green June beetle larvae were exposed to RDX and phenanthrene through-out their entire soil-bound development, starting within the first few days of hatching through to their emergence as adults. The overall findings included that even at high concentrations, RDX and phenanthrene (25 ppm) exerted no significant effect on body weight or survival. Also, there was lit-tle apparent effect of RDX and phenanthrene on the bacterial microbiome, and no statistical association with measurable health effects. Nevertheless, the green June beetle is an interesting model for soil toxicity experiments in the future as is it easy to collect, house, and handle.

Scarabaeid Pests: Subfamily Cetoniinae

This chapter discusses the green June beetle, which is a member of the order Coleoptera, family Scarabaeidae, subfamily Cetoniinae. Adults of this subfamily have the epimeron of the mesothorax visible from above. This beetle feeds on ripe, thin-skinned fruits. Another closely related species, C. mutabilis, is called the figeater and is sometimes confused with the green June beetle. Historically, the green June beetle was considered a turfgrass pest of regional importance, but activity of this species has increased on turfgrass throughout the eastern United States. Turf damage by this insect primarily is mechanical rather than being caused by feeding; the large (third-instar) grubs disrupt the soil surface by burrowing in the soil and producing mounds. This activity makes mowing difficult and, by exposing and damaging turf roots, can lead to turf loss caused by desiccation and disease.