Seasonal and Latitudinal Adaptations in the Life Cycles of Crickets

Abstract

In the temperate regions, crickets usually have well-defined seasonal life cycles. Their developmental stages occur every year in a regular sequence in relation to the seasonal changes, and the individual life cycles in each species are more or less synchronized. Among those species inhabiting the main part of the Japanese islands to the north of 30° N, only Gryllodes sigillatus and Myrmeeophilus sapporoensis can be found at various stages throughout the year. The fact that these exceptional species are confined to special habitats protected from violent fluctuations of weather conditions, houses and ant nests, respectively, suggests that adaptation to temperate climates requires a definite pattern of seasonal life cycle. The latter is, of course, due to the existence in the life cycle of a particular stage highly resistant to a long period of arrested development. Adaptation to wide seasonal fluctuations in the environment is therefore not attained by a general increase in the tolerance range, but by the physiological division of the developmental cycle into the active and diapause phases with different optima of temperature, roughly corresponding to the summer and winter conditions, respectively (Browning, 1952a,b; Hogan, 1960a,b; Masaki, 1960, 1962, 1963, 1965; Rakshpal, 1962a,b,c, 1964).