Bacterial Symbionts play an important biological role in their host. G. lineatum harbor bacterial symbiont in the enclosed crypts of the midgut. It seems that the bacterial symbiont play important role in the insect. Therefore, in this study, the role of bacterial symbiont in the shield bug, Graphosoma lineatum (Heteroptera, Pentatomidae) was investigated. To do this symbiont elimination was performed using surface sterilization of the eggs. Then, we utilized age-stage, two-sex life table analysis to confirm the biological importance of bacterial symbiont in G. lineatum. According to our results symbiont removal had a significantly negative effect on the biology of the insect. These results clearly indicate this symbiont is essential for normal growth and reproduction.

Life table parameters

The age-stage specific survival rate (s_xj); the age stage specific fecundity (f_xj); the age-specific survival rate (l_x); the age-specific fecundity (m_x); and the population growth parameters the intrinsic rate of increase (r); the finite rate of increase (λ); the gross reproductive rate (GRR); the net reproductive rate (R₀) and the mean generation time (T) are calculated as mentioned in (Chi & Liu, 1985; Fathipour & Maleknia, 2016).

 The comparison of APOP and TPOP parameters was made by t- test using SPSS. To compute the population parameters (r, λ, GRR, R₀ and T), we utilized the TWOSEX-MSChart program (Chi, 2016). Moreover, the means and standard errors of the population parameters were calculated by using the paired-bootstrap (with 40000 resampling).