Emergence of the damselflies, Coenagrion mercuriale and Ceriagrion tenellum (Odonata: Coenagrionidae), at their northern range margins, in Britain

Abstract

Abstract. Emergence of Coenagrion mercuriale and Ceriagrion tenellum was examined in a mixed population at their northern range margin in Britain. Mortality at emergence was quantified in C. mercuriale. Consistent with their larval diapause characteristics, both species had an asynchronous emergence pattern, typical of "summer" species. Daily emergence of C. mercu riale was positively correlated with the duration of sunlight on the previous day (controlling for season) and its emergence period was found to be shorter than that observed in its core populations in Central and Mediterranean Europe. No differences were found between the patterns of emergence of the sexes in either species. Sex ratio at emergence differed significantly from 1:1 (at 1.35 : 1 -males : females) in C. mercuriale but not in Ceriagrion tenellum (at 1.04 : 1). Body size at emergence declined more steeply with time in females than in males of C. mercuriale because large size may confer a greater reproductive advantage in females (larger females may be more fecund) than males in non-territorial odonates. Percentage mortality of C. mercuriale at emergence was low (4.9% including deformed individuals), the main cause of mortality being deformity.

Strong cascading effect of weather conditions on prey availability and annual breeding performance in European bee-eaters Merops apiaster

“…In central Europe the majority of the preferred prey species of bee-eaters (Hymenoptera and Odonata, Krebs and Avery 1985;Arbeiter et al 2014) generally emerge from March onwards and reach their maximum abundances in mid-July until mid-August (e.g., Purse and Thompson 2003;Oertli et al 2005). Our study during this peak time revealed no temporal variation in insect availability during the months of high summer season (May-July) but spatial differences among habitat types with higher counts at the hedgerow and arable land (Fig.…”

“…However, there is no clear evidence for an adjustment of reproduction to the peak food abundance (Dunn et al 2011), probably due to unpredictable food supply during the nestling period (Cucco and Malacarne 1996b;Dunn et al 2011). Beeeaters cannot adjust laying in prospects of more favourable weather, because insect abundance can vary from day to day and will seasonally decrease in August (Purse and Thompson 2003;Oertli et al 2005). In addition, the late arrival and long nestling period allows only raising a single clutch per season (Lessells and Avery 1989).…”

Does Wind Affect Emergence Site Selection in Odonata?

“…Jakob & Suhling (1999) have shown that strong wind can damage dragonflies during emer-gence. Deformity of soft wings condemns odonates to death or to lower reproductive success (Purse & Thompson 2003). One idea is that the level of wind disturbance in certain forest (similar to wetlands) would be heterogeneous, i.e.…”

Emergence ecology ofOrthetrum cancellatum: temporal pattern and microhabitat selection (Odonata: Libellulidae)

“…The question of whether habitat selection at emergence differs between sexes has been raised in this study. One unusual finding is that body size increased with the emergence season; a result that is rarely found in previous studies (Banks & Thompson 1985;Inden-Lohmar 1997;Purse & Thompson 2003). Sugimura (1983) showed an increasing trend in body size in Deiela phaon from Japan; however, the sample size was too small.…”