Elimination of faecal bacteria by autoclaving: effects on insect attraction and development of their progeny in cattle (Bovidae) dung

Abstract Bacteria play a fundamental but often overlooked role in shaping insect communities in cattle (Bovidae) dung. To direct attention to this role, three experiments were performed with cattle dung autoclaved to reduce bacterial activity and the associated release of volatile organic compounds (VOCs) that attract coprophilous insects to deposits. In the first experiment, and consistent with expectations, fewer insects were recovered in pitfall traps baited with autoclaved versus control dung. In the second experiment, there was generally lower recovery of insects developing in autoclaved versus control pats colonised in the field. This result was attributed to reduced oviposition and lower survival of immature insects in the autoclaved pats. In the third experiment, no effect of autoclaved versus control dung was detected on the reproductive success of the dung beetle Onthophagus taurus (Linnaeus) (Coleoptera: Scarabaeidae), possibly because adults carry with them the requisite bacteria for larval development. In summary, faecal bacteria produce VOCs to directly affect the composition of the insect species that colonise and oviposit in cattle dung. The survival of their progeny is affected by faecal bacteria that provide a source of nutrients or may be pathogenic.