The holomediterranean speciesBacillus rossiusincludes many subspecific taxa, which can be characterized both on the basis of electrophoretic allozyme frequencies and egg chorionic pattern. At present, 8 subspecies have been identified; they are, following a clock‐wise direction from the south‐eastern to the north‐western:B.r. tripolitanusA,B.r. tripolitanusB,B.r. lobipes, B.r. montalentii, B.r. medeae, B.r. catalauniae, B.r. rossius,and B.r.redtenbacheri.Opercular details do not unequivocally specify intraspecific taxa, however these taxa sea can be clearly recognized from the fine chorionic SEM patterns of eggs laid by field collected females.B.r. tripolitanusA andB.r. tripolitanusB show a pattern of single small mamelons, while all the others have a ribbon design, more often with a lace‐net distribution. InB.r. redtenbacherisuch a pattern breaks down to give strings of different size mamelons. It would seem that the lace‐net ribbon pattern, owing to its frequent occurence and geographically wide distribution, is the ancestral one for the species. This also appears to be supported by comparative findings in related species such asB. grandiiand all the easternBacillusspecies. The ootaxonomical observations confirm electrophoretic evidence demonstrating that inB. rossiusparthenogenesis has arisen several times, independently in different areas of the species’ range.