Acrosternum hilare (Say) and Murgantia histrionica (Hahn) (Hemiptera, Pentatomidae) have vertically transmitted Erwinia-like bacterial symbionts in the posterior region of their midgut. We determined the impact of temperature (25°C and 30°C) on the biology of both insects and their symbionts. A. hilare showed higher mortality in the 1^st and 5^th instars at 30°C (26% and 6%, respectively) when compared with 1^st and 5^th at 25°C (12% and 2%, respectively); its developmental time was not affected by the temperature. Egg masses, 5^th instars and adults of A. hilare were symbiont-positive at 25°C, but those at 30°C were symbiont-negative from the 2^nd instar on. M. histrionica had similar developmental time at both temperatures, but 2^nd instar's mortality at 25°C (14%) was higher than at 30°C (8.7%). M. histrionica had 73.3% of 5^th instars positive for their gut symbiont at 25°C, but all were negative at 30°C. Our results show that 30°C affected the maintenance of this symbiosis in both insects. M. histrionica increased mortality at 25°C suggests that this association may be pathogenic and have a fitness cost. In summary, our data show that increased temperature cleared two pentatomid species of gut-associated symbionts and differentially affected their fitness.