“…It has long been considered as a complex of species because of differences in morphology, haemolymph pigments and response to photoperiod, and of results of cross-breeding experiments (Bund & Helle, 1960;Parr & Hussey, 1960;Boudreaux, 1963;Veerman, 1970Veerman, , 1974. Partial incompatibilities between closely adjacent populations were found in agricultural as well as in natural environments (Helle & Pieterse, 1965;De Boer, 1985), and might be related to the presence of Wolbachia (Tsagkarakou et al, 1996), an endosymbiont which is involved in cytoplasmic incompatibilities (Barr, 1982) and may be associated with genetic and phenotypic variation. Studies of nuclear gene polymorphisms at a restricted geographical scale have revealed patterns of isolation by distance and sometimes by host plant (Tsagkarakou et al, 1997(Tsagkarakou et al, , 1998.…”