The genus Velia belongs to the family Veliidae, a group of predatory true bugs within the infraorder Gerromorpha, the so-called semi-aquatic Heteroptera. These insects are medium sized, measuring between 4.2 and 9.4 millimeters for European species, and they possess a striking appearance: a dark blackish to reddish ground color, silver patches on the pronotum, and vivid orange to red patches on the abdomen. They are typical inhabitants of shaded stretches of small to medium rivers, where they can be observed from sea level up into mountainous areas, roaming across the water surface in search of prey. Despite their visibility in the environment, the genus attracted little taxonomic interest until Adriano Tamanini revised it in 1947, clarifying the identity of Velia currens and describing several other species, including all the congeners occurring in central Europe.

Before this new study, the Swiss fauna of aquatic and semi-aquatic Heteroptera was considered quite well-known. The collections of the main Swiss natural history museums had been revised, with particular emphasis on historically important holdings such as that of Nestor Cerutti, who collected between 1886 and 1940. A total of 60 species were recorded in Switzerland, although some were considered doubtful and in need of confirmation. Among the genus Velia, three species were listed for the country: Velia caprai and Velia saulii, both widespread in Europe and widely distributed in Switzerland, and Velia currens, which has a much more restricted distribution and had only been reported from the southern canton of Ticino.

The research emerged from an ongoing national project to map the aquatic beetles of Switzerland, which involves both field sampling throughout the country and the revision of museum holdings to verify the identity of historical records. While searching for beetles, the first author opportunistically collected specimens of Velia with a net and retained them for study. In parallel, material held in various museums, mainly in Switzerland but also in Italy, was examined. The institutions consulted included the Natural History Museum of Geneva, the Natural History Museum Bern, the Cantonal Museum of Natural History in Lugano, and the Kosmos Natural History Museum of the University of Pavia.

The results are remarkable on two fronts. First, the status of Velia gridellii in Switzerland has been brought up to date: recent collecting produced this species in four localities in southern Ticino, in the region known as the Sottoceneri, and it was even found in sympatry with Velia currens at Alto Malcantone. No historical specimen of Velia gridellii was found in any of the collections consulted, which strongly suggests that the species was simply overlooked in Switzerland rather than being a recent arrival. Second, the first record of Velia currens in Switzerland, published by De Carlini in 1887 based on material from Lugano and Ligornetto, has been revised and confirmed after the study of the original specimen collected in 1886.

That historical confirmation is a story in itself. The record by De Carlini predates Tamanini’s 1947 revision, meaning the identity of the specimens cited could not be verified at the time, and the record was overlooked by later reviewers of the Swiss fauna. The specimens cited by De Carlini may even have referred to another congener, potentially Velia gridellii. A single female collected by Pavesi in 1886, bearing the label Ligornetto Pavesi 86, was presumed to correspond to the specimen reported by De Carlini and was located in the entomological collection of the Natural History Museum of Pavia. When the second author revised this specimen, it did indeed belong to Velia currens, confirming a Swiss record that had waited nearly 140 years for validation.

Both Velia currens and Velia gridellii are considered Alpine-Apenninic Italian sub-endemic species. They are distributed mainly in Italy but also occur in neighboring countries such as Switzerland. Most records of both species lie in the Alpine and Apennine chains, although they can sometimes occur in areas close to the sea, for example where the Apennines reach the coast in Liguria and Calabria. More sporadically, they have been found in continental lowlands, but in these cases it cannot be excluded that specimens were carried down watercourses from higher ground. Velia currens pushes further north into the Alpine valleys and reaches higher altitudes, giving it a more montane distribution than Velia gridellii, which also occurs on Elba Island. In the Apennines, Velia gridellii already exceeds 1750 meters above sea level, and in the Alps it is generally found at lower elevations but may be expected to climb increasingly higher as climate change warms mountain habitats.

The Swiss distribution of the two species fits this pattern. Velia currens is found in Ticino and has so far only been recorded in the Sottoceneri, the southern part of the canton. The presence of Velia currens in the Aosta Valley suggests, as already noted by earlier researchers, that Velia gridellii could be present in the southern Valais near Simplon, in the Gondo region, as well as in parts of the Sopraceneri, the northern part of Ticino. The discovery of Velia gridellii in Ticino is not surprising, since the species has already been recorded in all the Italian Alpine foothills, including those near the Swiss-Italian border. The new data do not necessarily indicate a recent arrival driven by climate change, but it is likely that the species will expand its range northward in the coming years due to warming. Surveys in Italy have shown that adults of Velia gridellii are mainly active between June and November, and the individuals collected in Switzerland were found at the beginning of June and at the end of October, matching the reported start and end of adult activity.

Identifying these species requires technical skill, and in an intriguing twist, females of some Velia species are often easier to identify than males using external morphological features. Females of Velia gridellii are easily distinguished from the other Velia found in Switzerland by several features: the abdomen, in lateral view, is strongly upwardly directed with a typical saber shape; the ninth tergite, observed from behind, is semicircular rather than trapezoidal as in Velia currens; and the seventh connexivial segment is truncated. Males of Velia gridellii can be separated from those of Velia currens without difficulty, since the latter species has a trapezoidal ninth tergite whose truncated, non-circular terminal part is observable in dorsal view even without extracting the tergite. However, distinguishing the males of Velia gridellii from those of Velia caprai and Velia saulii is more challenging, because these species share a similar shape of the ninth tergite. The observation of the first tergites and the abdominal pattern can help, but the only certain features are the internal sclerites of the endophallus and the parameres. Species of this genus are also well characterized molecularly and by their DNA barcodes, offering an additional layer of confidence for future identifications.

The project on the faunistics of aquatic beetles in Switzerland, combining field sampling with museum revision, has thus yielded unexpected dividends for semi-aquatic bugs as well. The number of known Alpine-Apenninic Velia specimens increased by 85 percent, and new records grew by 75 percent. Even though specimens of Velia are very visible in the environment, they have not been the subject of extensive research: only a limited number of historic specimens collected in Ticino were deposited in the examined collections, and among the Alpine-Apenninic material, all belonged to Velia currens — no Velia gridellii had been collected in Switzerland before this study. With the discovery of Velia gridellii in Ticino, 61 species of aquatic and semi-aquatic Heteroptera are now recorded for Switzerland: 37 species of Nepomorpha and 22 species of Gerromorpha, with the addition of two species that still need to be confirmed, one for each infraorder. The authors hope that faunistic research on aquatic bugs will be encouraged by these results, proving once again that even in a densely studied country like Switzerland, careful fieldwork and patient museum detective work can still rewrite the map of life.

Subject of Research: The Alpine-Apenninic species of Velia Latreille, 1804: V. currens (Fabricius, 1794) and V. gridellii Tamanini, 1947 ( Gerromorpha , Veliidae ) in Switzerland

Article Title: The Alpine-Apenninic species of Velia Latreille, 1804: V. currens (Fabricius, 1794) and V. gridellii Tamanini, 1947 ( Gerromorpha , Veliidae ) in Switzerland

Article References: Cosandey, V., & Cianferoni, F. (2025). The Alpine-Apenninic species of Velia Latreille, 1804: V. currens (Fabricius, 1794) and V. gridellii Tamanini, 1947 (Gerromorpha, Veliidae) in Switzerland. Alpine Entomology, 9, 73-77. https://doi.org/10.3897/alpento.9.166667

Image Credits: AI Generated

DOI: 10.3897/alpento.9.166667

Keywords: Alpine-Apenninic, species, Velia, Latreille, currens, Fabricius, gridellii, Tamanini, Gerromorpha, Veliidae, Switzerland, scientific research