In uence of constant temperatures (15, 20, 25 and 30 °C) and thermoperiods (daily alternation of high (25 or 30 °C) and low (15 or 20 °C) temperature periods) on the maternal induction of progeny diapause was studied in females of the egg parasitoid Trichogramma telengai Sor. (Hymenoptera, Trichogrammatidae) under laboratory conditions. Two variants of each thermoperiod were tested: “short-day” (both thermophase and cryophase durations were 12 h) and “long-day” (thermophase and cryophase durations were 18 and 6 h, correspondingly). In addition, constant temperatures equal to the means of all thermoperiods were tested. The experiments showed that thermoperiods as well as constant temperatures have a substantial impact on the maternal photoperiodic response both in the interaction with various photoperiods and under constant darkness. However, T. telengai are evidently not able to perceive thermoperiods as a source of information on day length (and thereby on time of year).