A contribution to the Slovenian spider fauna – III

The study reports on first records of two spider species for Slovenian fauna, Zodarion rubidum and Prinerigone vagans from the Bela krajina region in southeastern Slovenia. Regarding their presence in the neighbouring countries and distribution in Europe, both species could be considered as expected. The finding of Z. rubidum during night time in the urban area demonstrates negligence of sampling at unconventional time and in anthropogenic habitats. Finding two new records during short term field survey also indicates undersampling of the spider fauna and supports the need for further faunistic work in the field of arachnology.

In the present work, we report on two new species for the Slovenian spider fauna, specifically Zodarion rubidum Simon, 1914 from the family Zodariidae and Prinerigone vagans (Audouin, 1826) from the family Linyphiidae.

Survey area
Sampling took place in Bela krajina, the region situated in southeastern Slovenia (Fig. 1). Bela krajina is mainly a karst area confined by the Gorjanci and Kočevski Rog mountain ranges in the north and west and the Kolpa River in the south and east. The area is a mosaic of agricultural land, forests, meadows and pastures.

Sampling methods, determination and specimen preparation
All specimens were collected with aspirator or forceps and preserved in denatured 70% ethanol. Determination, preparation and observation of the specimens with both light and electron microscopy were performed at the Department of Biology of the Biotechnical Faculty, University of Ljubljana. We used different determination keys for species identification (Roberts 1995, Nentwig et al. 2016, Oger 2016.
The epigyne of one female specimen was dissected and macerated in 15% KOH overnight to remove soft tissue. The prepared sample was inspected with Leica MZ FLIII stereo microscope and photographed by Leica DFC 425 C camera under 100× magnification.
For electron microscopic observation, the male specimen was briefly sonicated in ultrasonic bath PIO Sonis 2 T, air-dried, mounted on aluminium stubs and sputter-coated with platinum. The prepared samples were observed by Jeol JSM-7500F field emission scanning electron microscope.

Results and discussion
The two spider species, presenting the first records for Slovenia, belong to two different families, Zodariidae and Linyphiidae. They were found on one and two localities, respectively (Fig. 1). Like other members of the family Zodariidae, Z. rubidum specializes in ant-eating (Pekár & Křál 2002, Pekár 2004. Zodarion rubidum mimics red ants and often feeds on Myrmica sabuleti, Tetramorium caespitum or Lasius platythorax. It has up to 5 mm long body and hunts across open ground in the evening and during nighttime (Pekár & Křál 2002, Pekár 2004. Although it shows some spreading tendencies, the species is still considered Central-European (Nentwig et al. 2016). It has also been introduced to North America (Paquin & Dupérré 2006).  Prinerigone vagans (Audouin, 1826) (fam. Linyphiidae) Two males were collected by Alja Pirnat and Urška Ratajc on two locations in gravel bars of the Kolpa River on 24. 7. 2015. One male was collected from gravel bars near the Vinica village (45.45869°N, 15.25861°E; altitude: 168 m a. s. l.), the other from gravel bars near the Žuniči village (45.47973°N, 15.36656°E; altitude: 161 m a. s. l.). The specimens were identified based on the distinctive shape of their patellar apophysis and morphology of the distal parts of their pedipalps (Fig. 4).

Zodarion rubidum
According to the available literature, P. vagans is widespread in western and central Europe (Nentwig et al. 2016), although uncommon in England (Harvey et al. 2002, British Arachnological Society 2016. This species inhabits wet habitats, such as wet grassy meadows, shores of lakes and gravel bars (Harvey et al. 2002, Nentwig et al. 2016. Adult specimens are usually found throughout the year, but are most abundant early to mid-summer and autumn (Harvey et al. 2002, Nentwig et al. 2016).  According to known distribution and confirmed records in the neighbouring countries (Nentwig et al. 2016), the presence of both species in Slovenia could be expected. Finding of Z. rubidum in Bela krajina represents the southernmost record in the Balkans (Nentwig et al. 2016). The vicinity of the national border and high dispersal capabilities of spiders (Foelix 2011) imply the species may be present in Croatia, where it has not been recorded yet (Nentwig et al. 2016). The findings of the two new spider species in a relatively short survey period in July 2015 imply the Slovenian spider fauna is undersampled (Kostanjšek & Kuntner 2015). This supports the need for further faunistic work in the field of arachnology.