In Italy, the selenopid spider Selenops radiatus Latreille, 1819, was hitherto only known from the Aeolian Archipelago (northeastern Sicily), with a record from the island of Alicudi and plausible sightings from the island of Filicudi. In this paper, we present twenty-six new records from Sicily sensu stricto and its satellite islands, consisting of observations gathered from online naturalist networks and one adult specimen collected from the area where most observations were made. Nearly all records were made in buildings or similar artificial habitats, supporting the hypothesis that occurrences of S. radiatus are mainly limited to synanthropic environments in Sicily.
Selenops radiatus Latreille, 1819, ein Vertreter der Selenopidae, war bisher aus Italien nur von den Äolischen Inseln (nordöstliches Sizilien) belegt, mit einem Nachweis von der Insel Alicudi und plausiblen Beobachtungen von der Insel Filicudi. In dieser Arbeit werden 26 weitere Nachweise der Art von der Insel Sizilien wie auch umgebenden Inseln vorgestellt. Diese bestehen aus Beobachtungen, welche auf Online-Netzwerken zusammengetragen wurden sowie einem gesammelten Exemplar aus dem geografischen Bereich, woher die meisten Beobachtungen stammen. Nahezu alle Nachweise stammen aus Gebäuden oder ähnlichen künstlichen Lebensräumen. Dies unterstützt die Hypothese, dass Vorkommen von S. radiatus hauptsächlich auf synanthrope Lebensräume in Sizilien beschränkt sind.
The genus Selenops Latreille, 1819 (Araneae: Selenopidae) currently includes 132 species (World Spider Catalog 2024), most of them distributed in the tropical and subtropical regions of the world. For the Mediterranean region, only two species have been reported so far: Selenops bastet Zamani & Crews, 2019, recently described from Egypt and based only on females (Zamani & Crews 2019), and Selenops radiatus Latreille, 1819, the species examined in the present paper.
Selenops radiatus is distributed in Africa, the Middle East, India, Myanmar and China (World Spider Catalog 2024). It has been reported from the following countries of the Mediterranean basin: Egypt (Audouin 1826, El-Hennawy & Sallam 2019, Pickard-Cambridge 1876, Pavesi 1878, Simon 1899), Greece (Pavesi 1878, van Helsdingen 2023), Israel (Pickard-Cambridge 1872), Italy (only in Sicily) (Lo Cascio & Grita 2010), Lebanon (Simon 1884), Libya (Bosmans unpubl. in Nentwig et al. 2023), Spain including the Balearic Islands (Branco et al. 2019) and Türkiye (Kunt et al. 2011, Danışman et al. 2023). Here, we offer several new records of this species for Sicily (Fig. 1), including for the main island of Sicily based on a single collected specimen, and several additional observations by naturalists posted on various online platforms.
Material and methods
One specimen was collected by the author PG during field research activities. A Citizen Science approach was further used to gather all other data through photographic material kindly provided by the users of a zoology-oriented Facebook group, named “Fauna Siciliana” (hereafter FS, https://www.facebook.com/groups/faunasiciliana), managed by one of the authors (FPF).
The FS users provided data and locations of different S. radiatus individuals observed and photographed in Sicily. The present authors analysed every original picture, verifying the species identification and the locality provided, which were sometimes accompanied by further information about the surrounding habitat. Furthermore, observations available on the iNaturalist platform (hereafter iN; https://www.inaturalist.org/) were also gathered.
The specimen observed and subsequently collected by PG was examined under a stereomicroscope and preserved in a centrifuge tube fixed in 75% ethanol (Levi 1966). It is currently stored in the private collection of one of the authors (AD). It was photographed using a Sigma 105 mm f/2.8 Macro DG OS HSM Macro photo lens along with a Nikon D300s reflex camera and identified following Corronca (2002) and Nentwig et al. (2023). The only two Selenops species currently reported from the Mediterranean area are S. bastet Zamani & Crews, 2019 and S. radiatus Latreille, 1819. Given that S. bastet has only recently been described and it is only known from Egypt (Zamani & Crews 2019), while S. radiatus is known from the Aeolian Islands (Sicily), Iberian Peninsula, Greece and Türkiye (Nentwig et al. 2023), it is very unlikely that photographed selenopids in Sicily belong to a different species.
For the altitude, the mean (X), the standard deviation (SD) and the range (min–max) were calculated and reported as X ± SD (min–max). To avoid any confusion, for the main island of Sicily the term “Sicily sensu stricto (s. str.)” is used.
Material
ITALY: Sicily, Ragusa, Scicli, 36.7455°N, 14.7636°E, 120 m a.s.l., inside a rural warehouse surrounded by a dry and rocky habitat with low Mediterranean scrub vegetation and garrigue with Chamaerops humilis and Pistacia lentiscus on 18. May 2022, 1 ♀, P. Galasso leg.
Fig. 1:
Records of S. radiatus in Sicily (Italy). Localisation of Sicily south of the Italian Peninsula (a) and detail of Sicily (b): in yellow (circles), the first and only Italian records related to the Eolian Islands (Lo Cascio & Grita 2010); in red (circles), the new records found in Sicily; in green (triangle), location of the collected specimen. Maps by © d-maps.com, modified by means of ® Adobe Photoshop
All the other 26 new records were obtained as result of our analysis of photos provided by social networks (FS), inaturalist.org and personal communications by colleagues (Fig. 2), of which 16 (61.5%) are from locations in the province of Ragusa, south-eastern Sicily s. str. (see Fig. 1b). Five observations confirmed the presence of S. radiatus on Filicudi Island (see Lo Cascio & Grita 2010) and two of them, for the first time, prove its presence on the islands of Salina (Aeolian Archipelago; Fig. 3) and Pantelleria (Strait of Sicily) (Tab. 1, Fig. 1). The mean altitude of all the new records (n = 27) is 173.3 ± 148.3 (6–668) m a.s.l.; 26 out of 27 observations (96.3%) were made inside or immediately outside of buildings.
Tab. 1:
Data related to observations of S. radiatus in Sicily. Username followed by (FS): data collected from Fauna Siciliana Facebook group; username followed by (iN): data collected from iNaturalist platform, individually detailed in the reference list. Note: all data collected from both FS and iN are exclusively based on photographic material. The date and coordinates related to records from Filicudi by Lo Cascio & Grita (2010) were not reported by the authors. The coordinates related to records from Salina, inaccurate on the iNaturalist platform (see benedettagambioli 2022), were corrected by the corresponding author (B. Gambioli, pers. comm.).
Continued
Discussion
All the results here presented demonstrate a much wider distribution for S. radiatus in Sicily, with most records coming from the southeastern area of Sicily s. str. So far, the species was reported in Italy only for the small Alicudi Island (Aeolian Archipelago, Messina, Sicily), where it was described as “extremely common” (Lo Cascio & Grita 2010). Other reliable observations were made in Filicudi, another Aeolian Island (Lo Cascio & Grita 2010). The latter is now confirmed by five recent observations from the years 2019, 2020, 2021 and 2023 (Tab. 1).
Most individuals were observed inside or around inhabited houses (Fig. 3), just like the first record in Sicily (Lo Cascio & Grita 2010). This is in accordance with many observations from the Afrotropical region (Lawrence 1940, Corronca 2000, 2002). Our data clearly demonstrate the synanthropic habits of this species. In addition, Lawrence (1940) described the genus as being attracted by light and to be found resting on inside walls at night, which might further explain why it is frequently observed by citizens, but rarely collected by scientists.
Fig. 3:
One of at least six different individuals of S. radiatus observed inside the same inhabited house on the island of Filicudi (Aeolian Archipelago) in October 2023. Photo: I. Romano
This expansion pattern, linked to strictly anthropogenic environments, is very frequent in alien spiders (Nedvěd et al. 2011, Nentwig 2015) and can also be observed in several other non-native species in Europe (Faraone et al. 2019, Polidori et al. 2021, Sammet et al. 2021). The Sicilian records suggest that this species might be restricted to human settlement and an agricultural context in this region. On the other hand, other observations in the Mediterranean and Africa occurred in Eucalyptus plantations, where this species appears to be equally common in some areas (Corronca 1998, Kunt et al. 2011) demonstrating that S. radiatus might inhabit further heavily modified habitats in Sicily.
From the first Italian record (Lo Cascio & Grita 2010) to date, the known distribution of S. radiatus has substantially increased (Crews & Harvey 2011, Kunt et al. 2011, Bosmans & Van Keer 2017, Branco et al. 2019, El-Hennawy & Sallam 2019, Zamani & Crews 2019). Clearly, it remains unknown whether the species was introduced in some way to Sicily, for example through the transportation of goods, or whether its presence is to be considered historical on the island. With the exception of the sighting in Pantelleria in 2010 (see Tab. 1), the oldest observation in Sicily s. str. dates back to 2016, hence 6 years after the first Italian report from the Aeolian Islands.
All data collected, together with those presented here, suggest that this species is probably much more widespread in the Mediterranean area than previously thought. Future studies in other areas of the Mediterranean basin will most probably reveal new populations of S. radiatus.
Acknowledgements
We want to thank everybody who provided information, photos and data: Alessia Cicerone, Nadia Curcuraci, Angelo Ditta, Luisa Emmolo, Benedetta Gambioli, Rita Giuca, Alfonso La Rosa, Costantino Laureanti, Giuseppe Lo Sauro, Armando Maltese, Sofia Melluso, Francesco Ottaviano, Iacopo Romano, Gianni Sammito, Angelo Vaccaro and Maria Zocco. We also thank the following iNaturalist users: adrtry, benedettagambioli, elia35, gian53, io-es, pietro146, pemm and psimmons for sharing their observations on the platform. We are also grateful to our families, whose support is essential to us. We particularly thank Tobias Bauer and Filippo Milano who improved and corrected this paper.
