Effects of parental photoperiod and elevation on egg diapause, mortality, and synchronous hatching of Mormon crickets Anabrus simplex

Authors: Srygley, Robert

Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/31/2025
Publication Date: 8/4/2025
Citation: Srygley, R.B. 2025. Effects of parental photoperiod and elevation on egg diapause, mortality, and synchronous hatching of Mormon crickets Anabrus simplex. Journal of Insect Physiology. 165.104866. https://doi.org/10.1016/j.jinsphys.2025.104866.
DOI: https://doi.org/10.1016/j.jinsphys.2025.104866

Interpretive Summary: Mormon cricket eggs are unusual in that they can arrest development (diapause) and remain in the soil for multiple years without forming an embryo. Females are hypothesized to play a large role in determining the duration of egg diapause through adult photoperiod and selection of the egg laying environment, but no comparison of the effects of the parental and egg environment on diapause have been made. ARS scientists manipulated presented a mid-summer and late-summer light environment to the parents and buried eggs from these two genetic stocks at high (8,000 ft), mid (5,000 ft), and low (4,000 ft) elevations in the Bighorn Mountains. At high elevation, Mormon cricket eggs required six to eight years for 50% of them to develop and hatch, whereas the same genetic stock only required two to three years on average at the low elevation sites. Consequently, soil temperature is a critical factor in determining the persistence of Mormon cricket eggs in egg banks. Photoperiod, in contrast, only affected egg diapause at lower elevations with the eggs from late-summer parents developing faster than those of the mid-summer parents. Egg mortality was greater in eggs from late-summer parents at all sites, whereas fungal infection of eggs was only observed at high elevations. Because mountains provide a patchy thermal environment, multiple generations of eggs are likely to be banked in the soil in these regions, but egg banking at high elevations came at a cost of greater egg mortality. This research improves forecasting of Mormon cricket outbreaks to assist land managers in preparations for control efforts. It also points to the need to find new methods to locate and control Mormon cricket populations in egg banks to reduce the risk of synchronous hatching and migration of nymphs to arable lands.

Technical Abstract: Some katydid species remain in the egg stage for multiple years in prolonged diapause. Because the egg has yet to develop a nervous system, the parental generation is believed to play a large role in determining the duration of egg diapause through adult photoperiod and selection of the egg laying environment. However, little evidence exists that compares the relative influences of parental photoperiod and the egg environment on diapause. I investigated the relative effects of parental photoperiod and egg environment on diapause by burying two genetic stocks of Mormon cricket Anabrus simplex eggs, one from long-day parents and the other from short-day parents, at seven sites on an elevational gradient (1200-2800 m). As predicted, the effect of parental photoperiod on the diapause duration of the offspring was more pronounced at lower elevations than at high elevation sites. Contrary to results from a laboratory experiment, offspring of short-day parents developed faster. The field experiment confirmed that for Mormon crickets, parental photoperiod is a soft cue for prolonged diapause, especially when compared with the effects of the environment on egg diapause. Median hatching time ranged from two to eight years, depending on the elevation and microhabitat. Soil temperature was a critical factor in determining the persistence of Mormon cricket eggs in egg banks. Moreover, mortality was greater for the short-day photoperiod, particularly at higher elevations where the eggs were in the soil longer. At high elevation sites, the season for embryonic development is short and embryonic growth can only occur when the soil heats up during the day. Hence, multi-year diapause and slow embryonic development is a natural consequence of temperatures at high elevation. Mountains and canyons provide a patchy thermal environment where multiple generations of eggs are likely to be banked in the soil by which favorable environmental conditions can lead to developmental synchronization, hatching, and outbreaks.