Facultative and Obligatory Diapause Responses in Three Species of Burnet Moth: A Characterization of Life-Cycle Phenologies by Field Observations and Laboratory Experiments

Abstract

In temperate climates, phases of growth and dormancy of insect species must cope with the annually fluctuating weather conditions. Instead of quiescence, a prospective and hormonally controlled diapause prevents insect development outside of the season, even when environmental conditions are still advantageous. The induction, maintenance and termination of diapause as well as the resulting adaptive significance of various life-cycle strategies have been studied in detailed ecophysiological analyses (for recent reviews, see Danks 1987; Tauber et al. 1986; Zaslavski 1988). Many lepidopterous species respond to environmental factors during their larval instars, sometimes far in advance of the beginning of their diapause. Other species seem to develop independently of external cues (Friedrich 1983). Both extrinsic and intrinsic factors can regulate the life-cycles of these animals regardless of whether they are polycyclic species, with at least two generations within 1 year, or monocyclic species, with a single reproduction period every year (see e.g. Tauber and Tauber 1973).