The Pentatomidae is one of the largest families within the suborder Heteroptera (order Hemiptera), with over 4000 described species within eight subfamilies. Stink bugs are major pests of economically important crops worldwide including soybeans, rice, pecan, cocoa and macadamia nuts. Relationships between microorganisms and insects have been previously studied, but the majority of these associations remain poorly understood. In this book, I present molecular data showing that Nezara viridula, Acrosternum hilare, Murgantia histrionica, Euschistus heros, Chlorochroa ligata, Chlorochroa sayi, Chlorochroa uhleri, Plautia stali and Thyanta pallidovirens harbor a common dominant caecum-associated bacterial symbiont in their midgut. I also show that oral rather than transovarial transmission occurs by detecting the symbiont on eggshells after nymphs had hatched, instead of detecting symbionts in female ovarioles. Additionally, I demonstrated that these symbionts are polyphyletic suggesting that replacement of the symbiont may occur over time. Using a demographic approach I analyzed the effect of egg masses surface sterilization and temperature on the symbiont maintenance and on insect development of the pentatomids N. viridula, A. hilare and M. histrionica. Here I demonstrate that maintenance of the symbiont was affected by high temperature and egg mass surface sterilization for the species N. viridula, A. hilare and M. histrionica. N. viridula’s reproduction parameters were not significantly different between the surface sterilized and control treatments at three temperatures, however no reproduction was observed at 20ºC of the surface sterilized treatment. Survivorship and reproductive parameters for A. hilare were negatively affected by surface sterilization of egg masses and for higher temperatures. Conversely, no effect was observed for M. histrionica. Here I suggest that the degree of mutualism of this association for pentatomid species is variable, given the fact that A. hilare requires its symbiont for adequate development, while M. histrionica’s symbiont may not be significant in development of the host insect and N. viridula is not affected by deprivation of its gut-associated symbiont.