Estimation of the Annual Number of Generations of the Rice Bug, Leptocorisa chinensis Dallas (Hemiptera: Alydidae), Using the Development of Gonads and Formation of Endocuticle Layers after Adult Emergence

Abstract

Abstract:To clarify the timing of the appearance of overwintered and diapausing adults of the rice bug, Leptocorisa chinensis, under natural condition, we adopted two criteria, the developmental stages of gonads and the number of endocuticle layers in the cuticle of the hind-leg femur. Development of gonads after emergence was promoted in adults reared under a long-day photoperiodic condition, but suppressed under a short-day condition. The deposition rate of endocuticle layers was not influenced by the photoperiod but depended on age. These criteria were applied to estimate the annual number of generations of this species in Yamatsuri, Fukushima Prefecture, in 2006. According to these criteria, adults caught in early August, late August and early September were identified as an overwintered, newly-emerged and diapausing individuals, respectively. These data show that L. chinensis has mainly a univoltine life cycle in this region.

Diurnal locomotion activity of adult rice bug, Leptocorisa chinensis (Hemiptera: Alydidae), at different ages, measured by actograph and video camera

“…In the milkweed bug, it is reported that flight is depressed and feeding activity frequent during the teneral period, in which the cuticle layer hardens after adult molt and reaches full growth at 9-10 days (Dingle 1965;Caldwell and Rankin 1974). In L. chinensis, the teneral period is 7 days after adult molt (Matsuki et al 2010). It is possible that L. chinensis may also suppress locomotion activity and spend time feeding during this 7 days of the teneral stage, which corresponds to the duration of the ''settling mode''.…”