Determination of the variability in biological and behaviourial charactersin various populations of the three species of Sitophilus (Coleoptera : Curculionidae) living on stored cereals and their importance to characterize the species.

We have compared 38 different strains on wheat, from America, Europe, Asia and Africa, of the three Sitophilus species living on cereal grains or thei r by-products : S. granarius, S, oryzae and S. zeamais. Four biological cha racters were considered : weight of male and female, development time and f ertility, and three behavioural characters : the ability of male and female to fly, and the elimination of flour and feces out of the grains by the gr owing larvae. We also introduced aposymbiotic strains (6) in our analysis t o compare with the symbiotic ones. Multidimensional analysis placed these a posymbiotic strains, whatever their original species may be, in a same area , apart from the symbiotic strains. The three species granarius, oryzae and zeamais were clearly separated by the analysis with the used characters. N evertheless, if we consider the identification of a particular strain of Si tophilus, the risk of error is only 4,5 % between the two sibling species o ryzae and zeamais. Weight and flight were the two most important discrimina tion factors in this study. The variability was less important in strains b eing for a long time in the laboratory, than in "natural" strains. In zeama is and oryzae, we observed a negative relationship between weight and rapid ity of development. It was not possible to establish a clear relation betwe en the characteristics of strains and their geographical location. However, we observed some strains (Guadeloupe and Reunion) with intermediate charac ters between zeamais and oryzae.