Developmental parameters and photoperiodism in Trigonotylus tenuis (Reuter) (Heteroptera: Miridae)

Abstract

Developmental parameters and photoperiodism in Trigonotylus tenuis (Reuter) (Heteroptera: Miridae) were examined using wheat seedlings as food. The thermal threshold and effective cumulative temperature were 12.5°C and 91.9 day-degrees in the egg stage, 12.7°C and 155.8 day-degrees in the nymphal stage, and 11.7°C and 49.7 day-degrees in the preoviposition stage. Mean longevity of female and male adults at 25°C was 18.4 and 22.8 days, respectively, and a female adult laid 203 eggs on average. A temperature-dependent long-day photoperiodic response was observed in the maternal induction of egg diapause. At 17.5, 20 and 22.5°C, females showed a clear response to the photoperiod with a critical daylength of around 12.5 h/day; females reared under short-day conditions laid diapause eggs whereas those reared under long-day conditions laid nondiapause eggs. At higher temperatures (25, 27.5 and 30°C), however, females responded little to the photoperiod, irrespective of which they laid a high percentage of nondiapause eggs. Based on comparisons with T. caelestialium, a species closely related to T. tenuis, this photoperiodism is considered to be an adaptation to southern climates.