none The effect of temperature on developmental time of the palaearctic biotype of the solitary larval parasitoid, Apanteles rubecula Marsh., its longevity, parasitization rate and preference for larval instars of the host, Pieris rapae (L.) were studied in the laboratory. The duration of the internal development of A. rubecula from egg to cocoon lasted longer than the external pupal stage at all temperatures (15 degree , 20 degree , 25 degree C). The development from egg to adult emergence required 46.8 days at 15 degree C and 17 days at 25 degree C. The cocoon weight was highest at 20 degree C (5.8 mg) and only at 25 degree C differed between females and males. Female A. rubecula lived significantly longer (16.5 days) than males (6.1 days). There was no distinct preoviposition period and the oviposition period lasted about 17 days. In general parasitization was rather low, since at maximum 2.5 host larvae were parasitized per day. Only the first three larval instars of P. rapae were parasitized with the highest parasitization rate of 57% in the first and the lowest of 10% in the third larval instar.