In a study in western Norway, Calopteryx virgo were found to be infected by the eugregarine protozoan parasite Hoplorhynchus oligacanthus, with females more heavily infected than males (Abro 1996)
Svensson and Friberg (2007) studied the relative effects of predation by birds (wagtails, Motacilla spp.) on wing morphology of Calopteryx virga and C. splendens in sympatry in Sweden. Predation risk was almost three times higher for C. virgo (which has a much greater degree of wing melanization) than it was for the less extensively melanized C. splendens. The almost entirely black wings of C. virgo presumably make males of this species conspicuous to visual predators such as birds, thereby increasing male mortality rate. Wagtails appear to be driving natural selection favoring smaller wingpatch size in male C. virgo, i.e., a phenotype that is more similar to C. splendens. In addition to possibly influencing the evolution of wingpatch size in C. virgo, wagtail predation may directly benefit C. splendens. Because C. virgo is competitively superior to C. splendens in interspecific territorial interactions (Tynkkynen et al. 2005), selective predation on C. virgo by wagtails may have an indirect positive effect on C. splendens. (Svensson and Friberg 2007)
Koskimaki et al. (2004) carried out experiments with Calopteryx virgo to test the common hypothesis in behavioral ecology that the ability to defend a resource provides an indication of a potential mate's quality. Calopteryx virgo males defend territories containing one or more oviposition sites (emergent aquatic vegetation) where pair formation and guarded oviposition (egg-laying) occur. Territory ownership is settled by aerial contests that can be intense and prolonged between closely matched contestants.
Koskimaki et al. found that in staged contests between males, winners of the contests showed higher immunocompetence (measured as encapsulation in response to insertion of a 1.7 to 1.8 mm piece of nylon monofilament) and greater fat reserves. They also examined 29 males that had not been used in staged contests, and confirmed that in these males, also, encapsulation response correlated positively with an individual’s fat reserves. Thus, both immunocompetence and resource holding potential seem to depend on energy reserves, suggesting a trade-off between parasite resistance and energetically costly territorial behavior. (Koskimaki et al. 2004)
Tynkkynen et al. (2004) studied the evolutionary effects of geographic overlap between Calopteryx virgo and C. splendens in Finland, reporting three key findings. First, C. splendens males, which have pigmented iridescent blue wing patches which exhibit a high degree of both local and geographic variation (Tynkkynen et al. 2004 and references therein), were found to have smaller dark pigmented wing patches in populations with a high relative frequency of C. virgo (which have almost entirely pigmented wings and resemble C. splendens males with the largest wing patches) than in populations where C. virgo was relatively rare. Second, C. virgo males responded more aggressively to C. splendens with large wing patches than to those with small wing patches. Third, in all interspecific territory disputes, C. virgo won. Based on these results, Tynkkynen et al. suggest that interspecific aggression may have caused character displacement (a reduction in C. splendens wing patch size where it occurs with C. virgo) to reduce attacks by C. virgo males. This hypothesis is supported by experiments in which C. virgo were removed from some populations (Tynkkynen et al. 2005). Evidence suggests that mistaken species recognition may account for the interspecific territorial behavior observed in these two species (Tynkkynen et al. 2004, 2006).
The flight of C. virgo is butterfly-like, though heavier than that of C. splendens (Dijkstra and Lewington 2006).
The Beautiful Demoiselle (Calopteryx virgo) is a large, dark damselfly, with a very wide geographic distribution across Europe. It is typically found along small, clean, rapidly flowing forest streams, sometimes in large numbers, where it flutters about with a butterfly-like flight, settling frequently on trees and bushes along the stream border. (Askew 2004; Dijkstra and Lewington 2006)
Calopteryx virgo is found from western Europe east to Japan (although it is possible the Japanese form represents a distinct species) (Misof et al. 2000).
Askew (2004) gives the distribution of C. virgo as extending from the west of Scotland, Ireland, and Scandinavia south to North Africa, with the species (or superspecies) extending across Asia to Japan. Askew notes that the Japanese subspecies might better be recognized as a distinct species, C. japonica (Askew 2004 and references therein).
Dijkstra and Lewington (2006) state that C. virgo is locally common east to the Urals, but is absent from large areas in the south, such as on many islands, and in Anatolia it is mainly limited to coastal areas, rare on the plateau.
Dijkstra and Lewington (2006) report the flight season for C. virgo as May to late September.
Askew (2004) writes that in northern Europe C. virgo flies mainly from June and July until early August, but that in southern Europe it appears in May (or even late April) and may be seen until early September.
Calopteryx virgo prefers cooler running waters than other European Calopteryx, these streams being typically smaller, more shaded, or at higher latitudes. It is clasically found around small forest streams. Where streams broaden or open up, it may be replaced by C. splendens (with which it sometimes hybridizes). (Dijkstra and Lewington 2006) Calopteryx virgo flies slowly and settles frequently on trees and bushes bordering streams and rivers with clean, rather rapidly flowing water (Askew 2004).
Several forms of Calopteryx virgo are distinguished by wing color and are usually treated as subspecies, but in general this is the largest and darkest Calopteryx in Europe (Dijkstra and Lewington 2006).
Like other Odonata (dragonflies and damselflies), Calopteryx virgo has an unusual mode of reproduction involving indirect insemination and (like many insects and other animals) delayed fertilization. Sperm is transferred by the male from the tip of his abdomen (where it is produced) to secondary genitalia at the base of his abdomen, from which it is passed to the female during an acrobatic copulation in which the mating pair forms a "copulation wheel". Eggs are not fertilized until just before they are laid. (Dijkstra and Lewington 2006)
Wellenreuther et al. (2010) investigated possible impacts of climate change on hybridization rates between Calopteryx virgo and C. splendens. In some regions these two species are sympatric (i.e., they are both present), whereas in other regions only one or the other is present (i.e., they are allopatric). It is expected that as the climate warms, C. splendens will extend its range northward, eventually overlapping with C. virgo in northern Scandinavia. Wellenreuther et al. studied courtship responses of male C. virgo toward female C. splendens from sympatric populations with various proportions of C. virgo, as well as from allopatric populations. Male courtship responses of C. virgo toward conspecific females showed moderate geographic variation, but courtship attempts toward heterospecific C. splendens females increased significantly from sympatry to allopatry. The authors suggest that allopatric C. virgo males have partly lost their ability to discriminate against heterospecific females. Given this apparently reduced premating isolation in allopatry relative to sympatry, as ranges shift in response to climate change, bringing once allopatric populations into sympatry, an increase in hybridization (heterospecific mating) may result. (Wellenreuther et al. 2010)
Work by Tynkkynen et al. (2008) suggests that the majority of copulations between C. virgo and C. splendens (which appears to be regular, if not common, events) may be forced by males, or possibly be the result of female avoidance of harassment arising from persistent courtship displays of heterospecific males.
Cordoba-Aguilar (2002) and Rivera et al. (2004) discuss the ability of C. virgo males to displace the sperm of rival males from a female's sperm storage organs, including the limitations of this ability (males can remove rival sperm from the bursa copulatrix, the temporary sperm storage organ in the female, but sperm become inaccessible to the male once they have moved into the spermatheca).
