Termination of reproductive diapause in the rice water weevil with particular reference to the effects of temperature

Abstract

The period of diapause termination in adults (collected in Yueqing 120.94°E, 28.14°N, Zhejiang) of the rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), were determined by initially exposing diapausing adults to various constant temperatures (25-5°C) as well as to room temperatures (33-Ϫ1°C), and then transferring them at intervals to a climatically controlled chamber (26Ϯ1°C, using rice seedlings as adult hosts) where the dynamics of oviposition onset and the numbers of eggs deposited were observed. Under room temperature, the diapause in 1st-and 2nd-generation adults terminated around late September and early December, respectively, i.e. at ca. 2.5 and 2.0 months after collection. Diapause in both 1st-and 2nd-generation adults was significantly affected by temperature. When exposed to 10, 15 and 20°C, the diapause in most 1st-generation adults terminated after 75, 25 and 50 days, respectively, while in 2nd-generation adults it terminated after 50 days at each of these temperatures. The associated adaptive significance and geographical variation of diapause termination in this insect are discussed.

Oogenesis in summer females of the rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), in southern Zhejiang, China

“…Summer females could lay 60 eggs after they previously experienced 15 °C for 50 d (Jiang et al, 2004b). Compared with these females, the fecundity of summer females is apparently much lower, and they appear to be in a "transitional" state between diapause and reproduction.…”

Silvicultural treatment effects on oak seed production and predation by acorn weevils in southeastern Ohio

“…We also must consider that it is unlikely for weevil populations to remain stable through time. A number of studies have demonstrated variability in weevil diapause based on yearly changes in environmental conditions (Jiang et al, 2004;Higaki, 2006;Spurgeon and Raulston, 2006), and this could reduce the effectiveness of masting as a method for predator avoidance by circumventing the population reduction expected to occur during the lean period between mast years.…”

Japonica cultivars' susceptibility to the rice water weevil Lissorhoptrus oryzophilus (Coleoptera: Curculionoidea: Brachyceridae)

“…The insect's success in many different countries is attributed to its ability to undergo an adult reproductive diapause in cold winters (Jiang et al. ). Thus, it overwinters as an adult in or near rice fields, and after emergence in the spring begins feeding first on wild plants and then on rice.…”

“…The RWW has separate sexes only in its area of origin in North America; in California, Asia, and Europe, it is a parthenogenetic species (Saito et al 2005;Lupi et al 2007aLupi et al , 2010. The insect's success in many different countries is attributed to its ability to undergo an adult reproductive diapause in cold winters (Jiang et al 2004). Thus, it overwinters as an adult in or near rice fields, and after emergence in the spring begins feeding first on wild plants and then on rice.…”