Thermoperiodic control of diapause in two species of green lacewings (Neuroptera, Chrysopidae): comparative effect of sharp and smooth changes in temperature

摘要

Experiments conducted in Belgorod Province (50 deg N) with local populations of Chrysopa carnea and Ch. perla L. demonstrated that, in the dark, natural fluctuations in temperature induce diapause in all prepupae. In Ch. pallens, different artificial thermorhythms exert different effects on the incidence of diapause. When larvae are exposed to smooth thermorhythms with slow decrease and increase in temperature (same as under natural conditions) 100 percent of prepupae diapause independently of thecryophase and thermophase duration and amplitude (28-20 or 27-13 deg C). At 28-20 deg C sharp thermoperiod of the square-wave type, long cryophase induces diapause, and short cryophase causes active development. In Ch. perla, "long-day-type" thermoperiodic response is manifested both at sharp and smooth thermorhythm with amplitude of 28-12 deg C. However, smooth thermorhythm produces a weaker diapause-preventing effect. The role of the thermoperiodic reaction in the control of seasonal development in insects is discussed.