none no species Of 146 Sitobion avenae (F.) clones, collected in the surroundings of Kiel (Schleswig-Holstein, northern FRG) and exposed to artificial short day/low temperature conditions, 73% proved to be holocyclic, 3% paracyclic, 4% androcyclic and 20% anholocyclic. The relative amount of anholocycly differed between years (1985-87) and seasons: clones sampled in autumn showed a higher anholocyclic response than summer clones. Survival of anholocyclic S. avenae under outdoor conditions succeeded only during the mild winter 1987/88. High degrees of primary parasitism were recorded from S. avenae collected in volunteer cereals and early-sown winter barley fields between late summer and late autumn, whereas secondary parasitism remained unimportant. Aphidius picipes (Nees) was the dominant primary parasitoid, but other species of the same genus were also common. Aphidius spp. successfully parasitized both oviparae and males. Whole animal physiology; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Host parasite relationships; Abiotic factors; Physical factors; Land and freshwater zones; Palaearctic region; Europe Aphidius (Braconidae); Hemipteran hosts; Sitobion avenae; Parasite prevalence in autumn, implications; Prevalence; Sitobion avenae (Hemiptera) hosts; Season; Autumn, prevalence in hemipteran hosts; Germany; Kiel; Parasitism of Hemiptera, autumn prevalence Sitobion avenae (Aphidoidea); Dormancy; Overwintering strategies; Hymenopteran parasites; Aphidius; Prevalence in autumn, implications; Prevalence; Aphidius (Hymenoptera) parasites in autumn; Season; Autumn, hymenopteran parasite prevalence; Germany; Kiel; Overwintering & hymenopterous parasitism in autumn