Courtship behaviour of the polyphagous ectoparasitoid Lariophagus distinguendus Först. (Hymenoptera, Pteromalidae) was studied. The initial behavioural element of the courtship sequence is a characteristic wing fanning shown by the males at encounters with females. Wing fanning and arrestment of the males was elicited by paper discs treated with dichloromethane extracts from virgin females showing the existence of a female-derived sex pheromone. The pheromone is only active at a distance between 0-5 mm suggesting low volatility of the active compound(s). Females mate only once, and the pheromone is still perceived by males at least 5 days after female mating. Males exposed to dissected female heads, thoraces and abdomens, showed wing fanning towards all segments. However, extracts from female abdomens were significantly more active than those from heads or thoraces suggesting the pheromone source to be located in the abdomen.

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