European Journal of Entomology

The winter survival of three closely related univoltine heteropterans that overwinter as adults, Nabis rugosus, N. ericetorum and N. pseudoferus was investigated. After 150 days of low temperature treatment (3–5°C, 16L : 8D, r.h. 70–80%) more males than females died. The mortality rate ranged from 88.8 to 93.8% in males and from 54.2 to 60.7% in females. However, these sexual differences in mortality did not differ significantly across the three species and populations of different geographic origin. It remains a general question whether this considerable evolutionary stability in the sex-specific investment into reproduction and survival phylogenetically conserved or frequently evolves anew to similar levels in separated populations and species. In Nabis rugosus, the relative loss of body mass during overwintering was up to 37.8%. This reflects dramatic somatic costs of adult overwintering and indirectly supports the hypothesis that food supply during overwintering is important for some heteropteran predators. However, body mass before overwintering did not significantly explain the survival pattern in N. rugosus in either sex. The similar sex-specific survival rate of overwintering adult nabids regardless of species and geographic origin can be useful for studies on population dynamics of nabids in agroecosystems and biocontrol.

Address
Department of Biology, Ecological and Environmental Change Research Group, University of Bergen, Postbox 7800, N-5020 Bergen, Norway; e-mail: steffen.roth@macnews.de

Keywords
Winter survival, overwintering, low temperature experiment, sexual dimorphism, Nabidae, Heteroptera, Nabis rugosus, N. ericetorum. N. pseudoferus