Seven general kinds of life cycles are known among crickets; they differ chiefly in overwintering (diapause) stage and number of generations per season, or diapauses per generation. Some species with broad north-south ranges vary in these respects, spannig wholly or in part certain of the gaps between cycles and suggesting how some of the differences orgininated. Species with a particular cycle have predictable responses to photoperiod and temperature regimes that affect behavior, development time, wing length, boyd size, and other characteristics. Some polymorphic tendencies also correlate with habitat permanence, and some are influenced by population density. Genera and subfamilies with several kinds of life cycles usually have proportionately more species in temperate regions than those with but one or two cycles, although numbers of species in all widely distributed groups diminish toward the higher latitudes. The tendency of various field cricket species to become double-cycled at certain latitudes appears to have resulted in speciation without geographic isolation in at least one case. Intermediate steps in this allochronic speciation process are illustrated by North American and Japanese species; the possibility that this process has also occurred in others kinds of temperate insects is discussed.
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Richard D. Alexander (1968) studied this question.