none CARABIDAE-; COCCINELLIDAE-; Chrysopa carnea; INSECT-PREY; Metopolophium dirhodum & Sitobion avenae (Hemiptera); Influence of prey prevalence on plant host; POPULATION-DYNAMICS; BELGIUM-; Seasonal abundance, influence of hemipteran prey prevalence on plant host Aphidius rhopalosiphi; Praon volucre; HEMIPTERAN-HOSTS; Metopolophium dirhodum & Sitobion avenae; Influence of host prevalence on plant host; BELGIUM-; Seasonal prevalence, influence of hemipteran prey prevalence on plant host Metopolophium dirhodum; HYMENOPTERAN-PARASITES; Aphidius rhopalosiphi & Praon volucre; Influence of host seasonal prevalence on plant host; PLANT-HOSTS; Maize; Prevalence, effect of host variety, effect on predator & parasite abundance; INSECT-PREDATORS; Coleoptera & Neuroptera; Predator abundance, influence of prey prevalence on plant host, Belgium Sitobion avenae; PLANT-HOSTS; Maize; Prevalence, effect of host variety, effect on predator & parasite abundance; BELGIUM-; Prevalence on plant host, predator & parasite abundance relationship