Parental Photoperiod Affects Egg Diapause in a Montane Population of Mormon Crickets (Orthoptera: Tettigoniidae).

Abstract

Insect diapause is a state of arrested development persisting when conditions are favorable for growth. Prolonged diapause, which occurs when insects remain in diapause for multiple years, is uncommon. Mormon crickets Anabrus simplex Haldane, a katydid and pest of rangeland forage and crops, were thought to be biennial in the Bighorn Mountains of Wyoming, but they are able to prolong diapause in the egg stage for multiple years. To test whether parental photoperiod serves as a cue to prolong diapause, mating pairs from the Bighorn Mountains were set in the same daily temperature and humidity profiles with 20 pairs on short daylength (12:12 [L:D] h) and 20 on long daylength (15:9 [L:D] h). Almost every parental pair had some undeveloped eggs after two warm periods. Females in short daylength were not more likely to have eggs with a biennial life cycle, but they were more likely than those in long daylength to lay eggs with multi-annual life cycles. Parents on short daylength were more likely to lay inviable eggs. Other fitness measures, such as hatchling mass, nymphal survivorship, and adult mass were not different between parental treatments. Diapause termination distributed over multiple years probably constitutes a bet-hedging strategy in an unpredictable environment.