Ouden, A. den & J. van Roosmalen, 2011. Favorite hibernating spots of Sympecma fusca. Brachytron 14(1): 28-39. In the period between 2006 and 2011, hibernating Sympecma fusca have been studied at several sites in the Dutch provinces of Noord-Brabant, Limburg, Gelderland and Noord-Holland. Observations have been made on habitat preference and weather-driven behaviour of the species in winter. Furthermore, experience on the best search strategy was gained. Most hibernating damselflies of the inland populations were found in bushes of Calluna vulgaris or, less often, tussocks of Molinia caerulea. Most hibernating damselflies of the coastal dunes population were found on branches of Salix repens. All locations had a southward exposure in common, offering sunny conditions. They were all shielded from the wind by surrounding forest edges. The damselflies were most easily found during bleak weather conditions, when they are unable to turn away from the observer. The light-colored thorax and globular eyes are the features easiest to spot. During cold periods the damselflies choose lower positions in the vegetation compared to warmer periods. During snowfall they are often completely buried. Survival has been reported afternight temperatures down to -18 °C. The results of this study show many similarities with previous studies on hibernating Sympecma paedisca, although the latter species has been found to hibernate on locations much further away from suitable reproduction waters. Further study is required to obtain more information on hibernating Sympecma species and might help to explain the changing distribution patterns of these species in The Netherlands.

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André den Ouden, & John A.M. van Roosmalen. (2011). Favoriete overwinteringsplaatsen van Bruine winterjuffers (Sympecma fusca). Brachytron, 14(1), 28–39.