none The host plant affinities and allozyme variation of the gall wasp Diplolepis mayri (Schlechtendal 1877) in S Sweden are investigated and comparisons to the parthenogenetic D. rosae (Linnaeus 1758) are made. 2 electrophoretically distinct types of D. mayri , both clearly separated from D. rosae , were detected; a N' type which parasitizes Rosa majalis and R. villosa , and a S' type confined to R. rubiginosa . The systematic relationship between the 3 forms as indicated by the electrophoretic data differs from that implied by host plant specificity, parasitoids, and gall structure. Biochemistry; Proteins; Reproduction; Reproductive productivity; Genetics; Population genetics; Evolution; Variation; Associations; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Host parasite relationships Orthopelma mediator (Ichneumonidae); Hymenopteran hosts; Diplolepis mayri; Parasite occurrence in relation to plant host specificity Diplolepis mayri (Cynipidae); Enzymes; Hatching success; Plant host specificity relationships; Genetics of polymorphism and variation; Biochemical variation; Genetic variation; Allozyme variation in relation to plant host specificity; Mutualism; Periclistus brandtii & P. caninae; Inquilinism in relation to plant host specificity; Hymenopteran parasites; Orthopelma mediator; Parasite occurrence in relation to plant host specificity; Plant hosts; Rosa (roses); Host specificity in relation to allozyme variation; Host specificity; Rosa (plant); Allozyme variation relationships Diplolepis rosae (Cynipidae); Enzymes; Hatching success; Plant host specificity relationships; Genetics of polymorphism and variation; Biochemical variation; Genetic variation; Allozyme variation in relation to plant host specificity; Plant hosts; Rosa (roses); Host specificity in relation to allozyme variation; Host specificity; Rosa (plant); Allozyme variation relationships