Arachnologische Mitteilungen 56

Dimorphic males in Troxochrus scabriculus 49 stinguished between the nominate form Troxochrus scabriculus and the form T. scabriculus cirrifrons . Almost three decades later, Roberts (1987) briefly sum- marized the debate surrounding T. scabriculus / cirrifrons and pointed out that the male Troxochrus scabriculus forma cirri­ frons (page 74, Fig. 31b) differed from the typical form Troxochrus scabriculus (page 74, Fig. 31a) in the size and shape of the cephalic lobe and by the presence of long bristles lateral to each posterior median eye. According to Roberts (1987) there are, however, no significant differences in the male palps between these two forms, and accompanying females exhibit no significant differences in general appearance or genitalia. Concerning the females, there is only slight but insignificant variation in the epigynum of T. scabriculus . Roberts (1987) stated in his book on the spiders of Great Britain and Ireland that T. cirrifrons is a dimorphic male form of T. scabriculus , and he designated it as T. scabriculus f. cirrifrons . Nonetheless, he declined to synonymize the two species. Instead, he argued that this case would have to be ultimately resolved by bree- ding experiments. Recently, Aakra et al. (2016) found two additional dif- ferentiating morphological features between the two forms, which they considered as two species with reference to the World Spider Catalog (2018). First, males of T. scabriculus possess an extra set of glandular openings on each side of the field of short hairs above the anterior median eyes (Aakra et al. 2016, Figs. 22A–D), while no such structures are visible in T. cirrifrons . Second, considerable differences were noted in the invaginations of the sulci, which are much larger in T. cirrifrons than in T. scabriculus (Aakra et al. 2016, Fig. 22E). The case of T. scabriculus / cirrifrons is not the only taxono- mic example within the family Linyphiidae of male morphs having different head forms within one species, without there being differences in genital morphology. Recently, Bosmans & Oger (2018) confirmed Diplocephalus cristatus as a dimor- phic species, having two male morphs: cristatus and forami­ nifer . Other examples are Diplocephalus conatus / jacksoni and Oedothorax gibbosus/tuberosus (see Roberts 1987).Wunderlich (2008) added further examples of species from the family Li- nyphiidae, in which the male prosoma has two or more dif- ferent shapes (i.e. lobes) and/or hairy areas, and he explicitly considered T . cirrifrons as a variation (or “form”) of T. scabri­ culus [“ Troxochrus scabriculus (= cirrifrons )”]. Thus, the phenomenon of dimorphic males in spiders must be considered as an established fact. As a result of these consi- derations and based on the examination of our own material, we now follow the original assessment of Simon (1884) and conclude that the cirrifrons male is a second male morph of T. scabriculus . Since there are no differences in the genital mor- phology between male specimens of cirrifrons and scabriculus , and since there are no differences in the females of different populations, we consider Troxochrus cirrifrons (O. Pickard- Cambridge, 1871) to be a junior synonym of Troxochrus sca­ briculus (Westring, 1851) and consequently, the male morph cirrifrons as a second form of the nominal T. scabriculus . We are not the first to arrive at this conclusion. For ex- ample, Müller (1984) clearly regarded T. scabriculus and cirri­ frons as not being distinct species since their male genital morphology is identical, and he also did not consider them as sub-species (as suggested by Heimer 1976) due to their sympatric occurrence. In several checklists T. scabriculus and T. cirrifrons have been treated as synonyms. Yet in the checklist of spiders of Germany, Platen et al. (1991) listed T. scabriculus and cirri­ frons as two distinct species. In the checklist four years later, Platen et al. (1995: 36) considered T. cirrifrons as a synonym of the typical T. scabriculus ; and again, in Platen et al. (1999: 25) T. cirrifrons is defined as a synonym of T. scabriculus . Not- withstanding the fact that T. cirrifrons was recorded in Berlin (von Broen 1977), Platen & von Broen (2002) no longer lis- ted T. cirrifrons in the checklist of the spiders of Berlin. Likewise, in the checklists of the spiders of Russia, Mik- hailov (1996: 99; 1997: 102; 2013: 96) consistently mentioned T. cirrifrons (O. Pickard-Cambridge, 1871) as a (junior) syno- nym of T. scabriculus (Westring, 1851).This is also true in the provisional atlas of the British spiders by Harvey et al. (2002). In the caption to the map of records of Troxochrus scabriculus , Harvey et al. (2002: 116) commented that any record sub- mitted to the scheme as T. cirrifrons (O. Pickard-Cambridge, 1871) under BRC number 15301, is now considered to be a form of male T. scabriculus . Thus, we can summarize that T. cirrifrons (O. Pickard-Cambridge, 1871) has been repeatedly considered to be a form of male T. scabriculus in several nati- onal spider checklists. However, there are spider checklists of other countries or regions where T. scabriculus and T. cirrifrons are still listed as separate species, e.g. in the departments “Nord” and “Pas-de- Calais” of northern France (Lecigne 2016: 56), in Flanders (Maelfait et al. 1998: 136), Belgium (Bosmans 2009: 52, Bos- mans & van Keer 2017), the Netherlands (van Helsdingen 1999: 156, 2016: 111) and Bulgaria (Blagoev et al. 2002- 2018); and of course, in the World Spider Catalog (2018) T . cirrifrons and scabriculus are still considered two separate species (see also Bosmans & Oger 2018: 52). Material examined The epigeic spider fauna of six overgrown gardening plots (study sites A–F) on the rooftop of the “Biozentrum Althan- straße” in Vienna, Austria, was examined from 8 April 2016 to 7 April 2017 by means of one pitfall trap per site (Mila- sowszky & Hepner 2017). Troxochrus scabriculus / cirrifrons material: AUSTRIA: 100 )) (95 scabriculus , 5 cirrifrons ), 34 (( , Vienna, Alsergrund, Biocenter Althanstraße, UZA1, rooftop, overgrown garde- ning plots, ruderal sites, 176 m a.s.l., M. Hepner & N. Mila- sowszky leg. & det., M. Hepner collection. After identifying the material of male scabriculus and cirri­ frons available to us, we completed drawings of the prosomas in lateral and frontal views from both morphs (Figs 1a–d). Additionally, we provide drawings of the female genitalia, i.e. the epigynum and vulva (Figs 2a–b). For views of the iden- tical-looking palps of scabriculus and cirrifrons males see Figs 3a-b. Habitat and distribution Platen et al. (1991) listed T. scabriculus and T. cirrifrons as two distinct species, however, the information provided for both with regard to habitat was identical, i.e., plant formati- on: subatlantic broom-heathland, sand dry grassland, couch grass-meadows and persistent ruderal areas. Furthermore, both species or forms were characterized as xerophilic inhabi- tants of the soil-surface with a peak of activity in the summer