Arachnologische Mitteilungen 56

Dimorphic males in Troxochrus scabriculus 51 months (mid-June to mid-September). Müller & Schenkel (1895) reported T. scabriculus and T. scabriculus cirrifrons adult male forms under the taxon T. scabriculus ; both forms were collected from October to December in an alder forest along a meadow riverbank in Switzerland. Also, Thaler (1986) do- cumented that both forms occurred together in a black alder forest near Vienna (Austria), where, 69 males of the form sca­ briculus and two males of the form cirrifrons were collected. Steinberger & Thaler (1990) collected one cirrifrons male in a small relictual floodplain forest strip on the left riverbank of the river Inn in Tyrol (Austria). Interestingly, T. scabriculus males were present in the same area, but not in the same study sites, in contrast toThaler (1999), who considered the records in the two study sites as evidence of sympatric occurrence. In Denmark, Larsen & Bøggild (1970) noted sympatric occurrences of T. scabriculus and T. cirrifrons from sand dunes and marram grass.Wiehle (1960) related that one male of the form cirrifrons was on the southern slope of the “Kyffhäuser” mountains in Germany, 4 October 1958, and another male in a salt meadow (Salicornietum) near Hecklingen-Anhalt, 12 June 1958. Von Broen (1977) reported T. scabriculus / cirrifrons from a “Ligusterhecke” [privet hedge] in Berlin, Germany. In the “Niederrhein”-Lowland, Otrembnik (1978) secured one T. scabriculus f. cirrifrons male and one female in a riparian grassland and seven T. scabriculus f. cirrifrons males and one female in a fertilized nutrient-rich meadow; however, no re- cords were made of the typical male form. In Aldenhoven, Germany, Esser (1997) collected two cirrifrons males together with 64 T. scabriculus specimens (probably mostly males) in a small ryegrass-plantain field margin strip (300 m length, 3 m width) situated between an arable field and an asphalt road. In Renkum, a town in the eastern Netherlands near Arnhem, van Helsdingen & IJland (2008) discovered a single male in a former arable grassland field between 1 April and 31 October 2008. Dekkers-Scheutjens (2010) obtained 31 T. scabriculus males in a study site within a nature reserve southwest of Til- burg, together with three cirrifrons forms. According to Harvey et al. (2002), T. scabriculus is restric- ted to dry habitats in the British Isles, such as calcareous grass- land, quarries, river shingle, haystacks and bare ground. The spider is a typical inhabitant of sand dunes where it prefers dense clumps of marram grass; in gardens the species can be encountered on gravel paths (Harvey et al. 2002). Mikhailov & Trishina (2013) observed one T. cirrifrons male form co- occurring with one male and two females of T. scabriculus in a birch and lime tree plantation in the vicinity of Pushta (Mor- dovian Republic, Russia) on 19 August 2011. In Norway, T. cirrifrons inhabited the same type of habitat as T. scabriculus , i.e. open sand and shingle (= gravel) dominated localities near rivers, streams and the seashore (Aakra et al. 2016). Entling et al. (2007) compared 224 Central European spider commu- nities along two major environmental gradients, i.e. shading and moisture. Within the shading gradient from open habi- tats to forests, T. scabriculus and T. cirrifrons had very similar Fig. 4: Phenology of Troxochrus scabriculus males (forma scabri- culus and forma cirrifrons ) and females in 13 study periods between 8 April 2016 and 7 Ap- ril 2017 on the rooftop of the “Biozentrum Althanstraße” in Vi- enna (Austria). Black bars: T. sca- briculus f. cirrifrons males; Grey bars: T. scabriculus f. scabriculus males; White bars: T. scabriculus females.