ORIGINAL CONTRIBUTION The effects of habitat, density, gender and duration on overwin- tering success in Bembidion lampros (Coleoptera: Carabidae) M. Knapp 1 & P. Saska 2 1 Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Prague, Czech Republic 2 Crop Research Institute, Prague, Czech Republic Introduction In temperate climates, winter is a period of increased risk to the survival of arthropods. These animals must cope with hostile abiotic conditions, particu- larly low temperatures. Low temperatures not only directly cause death to species with a lower ‘cold- hardiness’ (Sinclair et al. 2003) but also modulate predator–prey dynamics (Korenko et al. 2010). Win- ter mortality may reach up to 90% in many arthro- pod species (Leather et al. 1993), making overwintering a key phase in their life cycles. Arthropods have developed a range of behavioural mechanisms to cope with harsh winter conditions. They increase their chances of successful overwinter- ing by occupying suitable microhabitats (Dennis et al. 1994; Pywell et al. 2005) that buffer tempera- ture fluctuations, avoid extreme minimum tempera- tures (Luff 1965, 1966) and reduce the risk of flooding and the risk of predation (Korenko and Pekar 2010). Some arthropods lower their tempera- ture thresholds for activity so that they can search for prey under conditions at which other species have become inactive (Korenko et al. 2010). Studies have shown that many generalist preda- tors inhabiting arable fields (e.g. carabid beetles) strongly prefer overwintering sites that are outside of the fields (Dennis et al. 1994; Andersen 1997; Collins et al. 2003a). However, the intensively man- aged agricultural landscapes of many European Keywords body condition, fitness, ground beetles, intraguild predation, longevity, survival Correspondence Michal Knapp (corresponding author), Department of Ecology, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamycka 129, Praha 6 – Suchdol, 165 21, Czech Republic. E-mail: kapon@atlas.cz Received: January 25, 2011; accepted: April 27, 2011. doi: 10.1111/j.1439-0418.2011.01643.x Abstract In temperate climates, winter mortality is a key factor influencing insect survival. In Bembidion lampros (Coleoptera: Carabidae), an abundant polyphagous predator in arable farmland, we investigated how habitat, population density, gender and duration of overwintering affect the winter mortality and body condition of survivors. In a field experiment, we introduced beetles at two population densities into isolators placed either in the interior of the field or in the grassy boundary. Half of the isolators were collected in mid-March, and the remaining half were col- lected in mid-April. Across all treatments, 44–92% of the beetles sur- vived until spring. Survival was significantly higher in the field interior than in the boundary. The longevity of individuals starved after over- wintering was higher in females than in males and was positively related to the length of time spent at the overwintering site. Population density was positively related to percentage survival but did not affect body condition. Our results suggest that biotic factors such as population density and predation, though little studied, may have a similar signifi- cance as abiotic factors. Even ubiquitous carabid species inhabiting agro- ecosystems have specific requirements for overwintering. Understanding these requirements is useful for developing techniques to support their overwintering success. J. Appl. Entomol. J. Appl. Entomol. 136 (2012) 225–233 ª 2011 Blackwell Verlag, GmbH 225