Non-consumptive killing of distasteful pests: Are spiders engaging in superfluous killing of stink bugs?

The brown marmorated stink bug (Halyomorpha halys) (Hemiptera: Pentatomidae) is rapidly becoming an economic and nuisance pest in the eastern United States. With the desire to develop natural biological control options, there is a need to identify key natural enemies of these stink bugs to develop viable control options. Spiders are known predators of other stink bugs, including Oxyopes salticus (Araneae: Oxyopidae) which routinely consume stink bugs and is common in agricultural ecosystems. Despite the plethora of studies confirming the existence of this trophic pathway, it is unclear if spiders are having any discernible impact on stink bug populations. Molecular gut-content analysis revealed a small percentage of spiders were feeding on stink bugs but superfluous killing and partial consumption could further aid pest control and over 80% of spider limiting effects on prey can be attributed to predator-induced effects and superfluous killing. To test the effect of spiders on stink bug populations, field cage studies were conducted. Results showed a significant reduction in stink bug populations after field-cages containing spiders, revealing that the presence of spiders  can provide a valuable biological control service of stink bugs. This contrasts to the molecular gut-content results that indicate negligible consumption rates, suggesting that superfluous killing is the likely causative factor responsible for spiders reducing stink bug populations.