## 4 Discussion  
The results of this present study showed that the coexistence can affect the progeny production by the two _Sitophilus_ species that share the same cereal. The number of progeny production of both species was negatively affected by the presence of a competitor from the same genus. In an earlier study, [PERSON] et al. [12] examined different Pospoctera species of the family Liposcelididae, e.g., _Liposcelis bostrychophila_ ([PERSON]), _Liposcelis decolor_ ([PERSON]), and _Liposcelis paeta_ [PERSON] (Psocoptera: Liposcelididae) and showed that the presence of _L. bostrychophila_ has reduced the population growth of the other species at all temperature levels tested, suggesting a vigorous displacement. Moreover, [PERSON] et al. [2] recorded a lower number of adults when _S. oryzae_ and _S. granarius_ were combined, as compared with the occurrence of only one species for both rice and maize, while _S. oryzae_ was the species that produced the higher number of offspring. In a similar work, [PERSON] [26] tested the competition between _S. oryzae_ and _S. granarius_ in different commodities and underlined that _S. oryzae_ was, in all combinations, the dominant species. In our study on wheat, progeny production of _S. oryzae_ was higher than that of _S. granarius_, regardless of the simultaneous presence of both species in the same vial, which is in accordance with the previous reports. Moreover, we have found that the simultaneous presence of _S. oryzae_ had a negative effect on the progeny production of _S. granarius_ in terms of adult emergence from the grain kernels. This is partially due to the fact that _S. oryzae_ is able to produce more progeny than _S. granarius_ when the prevailing conditions are favorable [2]. At the same time, at the temperature range tested here, _S. oryzae_ was able to complete its life cycle faster than its conspecific [27], which played an important role in the timing of adult emergence that will subsequently cause grain damage. The shorter developmental range and higher progeny production capacity may be also the reasons why _S. oryzae_ was able to produce more progeny than _S. zemais_ in a similar series of experiments in both rice and maize [12], although the difference in offspring emergence between these two species was much narrower than the one recorded here. Nevertheless, at 120 days of incubation and at 25 \({}^{\circ}\)C, we noticed that on barley progeny production of _S. granarius_ was high. In this context, taking into account longer incubation periods, the latter species may have higher population growth, especially at 25 \({}^{\circ}\)C, which is closer to its optimum developmental threshold, which is much lower than that of _S. oryzae_ or _S. zemais_[28]. It is generally expected that the incubation period is critical for progeny production of different stored product species as it is related to the development rate and the succession of more than one generation that boosts population growth [23; 29; 30]. In our case, the increase in the incubation period to 120 days showed an increase in progeny production in some combinations when species were alone, but this trend was not expressed that vigorously when the two species were combined together, suggesting that competition might have \"concealed\" these trends. Paradoxically, we found that progeny production in relation to the incubation period was commodity mediated, as there were cases where progeny production was higher on barley at the 65-day interval compared to the 120-day one, with the opposite being recorded for wheat. Still, the commodity may not be the determinative factor here, as we have observed fungal development in some of the vials, which might have caused a detrimental effect on the population growth of both species. [PERSON] et al. [31], testing the competition between _P. truncatus_ and _S. zemais_ on maize, also found a wide range of fungal species after the incubation period, especially in the vials that contained the latter species. Previous studies have documented that _S. oryzae_, _S.