none. Palexorista laxa; HYMENOPTERAN-PARASITES; Tetrastichus howardi; Facultative hyperparasitism; HYPERPARASITISM-; Facultative hyperparasitism by Tetrastichus (Hymenoptera); Host preference, influencing factors Chilo partellus; Helicoverpa armigera; HYMENOPTERAN-PARASITES; Tetrastichus howardi; Preference over parasitism of Xanthopimpla & dipteran host, influences Tetrastichus howardi; DIPTERAN-HOSTS; Palexorista laxa; HYMENOPTERAN-HOSTS; Xanthopimpla stemmator; Facultative hyperparasitism; LEPIDOPTERAN-HOSTS; Chilo partellus & Helicoverpa armigera; Preference over parasitism of Xanthopimpla & dipteran host; HYPERPARASITISM-; Facultative, assessment of host preference, influences Xanthopimpla stemmator; HYMENOPTERAN-PARASITES; Tetrastichus howardi; Facultative hyperparasitism, assessment of host preference, influences Tetrastichus howardi (Olliff) preferred the lepidopteran hosts, Chilo partellus (Swinhoe) (Pyralidae) and Helicoverpa armigera (Hubner) (Noctuidae) to their parasitoids, Xanthopimpla stemmator (Thunberg) (Hymenoptera: Ichneumonidae) and Palexorista laxa (Curran) (Diptera: Tachinidae). If T. howardi had previously experienced parasitising a certain host, its preference for that host increased, but not significantly. When reared on a certain host, the preference for that host increased. T. howardi showed no preference to any particular age of its hosts. T. howardi was able to discriminate between parasitised and unparasitised hosts, initially preferring parasitised hosts, but two days later preferring unparasitised hosts.