Physiological Entomology (2010) 35, 128–133 DOI: 10.1111/j.1365-3032.2009.00719.x Mating experience weakens starvation tolerance in the seed bug Togo hemipterus (Heteroptera: Lygaeidae) CHIHIRO HIMURO ∗ and K E N J I F U J I S A K I Laboratory of Insect Ecology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan Abstract. Organisms are exposed to various stresses caused by environmental fluctuations. One of the most common stresses is the shortage of food. Individuals of many species must survive periods of starvation. There appears to be a trade-off between reproduction and survival. When residual reproductive value declines for an individual, life-history theory predicts an increase in current reproductive investment. Current reproductive investment differs between virgin and mated individuals. It is likely that mating experience influences starvation tolerance. However, few studies have investigated sex differences in the effect of mating experience on starvation tolerance or clarified the causes of reductions in starvation tolerance in both sexes. In the present study, these questions are investigated using the seed bug Togo hemipterus (Heteroptera: Lygaeidae).The results of the present study demonstrate that mating is costly for both sexes. Mated males show very short survival times and a daily reduction in weight, and daily energy expenditures are significantly greater in mated males than in virgin males. It is possible that starvation increases the mating effort of males, such as behavioural activities and the amount of time spent searching for females. A trade-off between survival duration and lifetime fecundity is found in virgin females. However, there is no trade-off in mated females, which have very short survival times. Whether male seminal substances contribute to the short survival times of mated females is considered. This is the first report demonstrating the influence of sex and mating experience on starvation tolerance. Sex-specific causes for reductions in starvation tolerance are discussed. Key words. Mating effort, mating experience, seminal fluid, sexual difference, starvation tolerance, Togo hemipterus. Introduction Natural environments change frequently and organisms are exposed to various stresses, such as desiccation, high humidity, high or low temperatures and starvation, as a result of environmental fluctuations (Hoffmann & Parsons, 1991). These stresses influence individual survival and can reduce fitness Correspondence: Chihiro Himuro, Laboratory of Insect Ecology, Graduate School of Agriculture, Kyoto University, Oiwakechou, Kitashirakawa, Sakyo-ku, Kyoto, 606-8502, Japan. Tel.: +81 75 753 6147; fax: +81 75 753 6474; e-mail: chimuro@kais.kyoto-u.ac.jp *Present address: Laboratory of Insect Ecology, Graduate School of Environmental Science, Okayama University, 1-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan (Koehn & Bayne, 1989). Insects have evolved elaborate behavioural and physiological responses as adaptations to stresses. Some species migrate to new habitats and others develop tolerance behaviours, such as diapause and quiescence (Hoffmann & Parsons, 1991). One of the most common stresses experienced by animals is the shortage or suboptimal quality of food. Individuals of many species must survive periods of starvation or exposure to suboptimal diets. Starvation tolerance is reported for many arthropod species, such as spiders (Anderson, 1974; Tanaka et al., 1985), mantises (Moran & Hurd, 1997), water striders (Rowe et al., 1994) and Drosophila (Hoffmann & Parsons, 1991; Djawdan et al., 1997; Karan et al., 1998). Individu- als reduce their metabolic rate and reduce egg production as adaptations to starvation (Juliano, 1986; Djawdan et al., 1997).  2010 The Authors 128 Journal compilation  2010 The Royal Entomological Society