Phantom spiders : notes on dubious spider species from Europe

A surprisingly large number of European spider species have never been reliably rediscovered since their first description many decades ago. Most of these are probably synonymous with other species or unidentifiable, due to insufficient descriptions or missing type material. Here we discuss about 50 of these cases, declare some names as nomina dubia and establish the following new or re-confirmed synonymies: Agelena mengeella Strand, 1942 = Allagelena gracilens (C. L. Koch, 1841) syn. conf.; Anyphaena accentuata obscura (Sundevall, 1831) = Anyphaena accentuata (Walckenaer, 1802) syn. conf.; Anyphaena accentuata obscura Lebert, 1877 = Anyphaena accentuata (Walckenaer, 1802) syn. nov.; Araneus diadematus stellatus C. L. Koch, 1836 = Araneus diadematus Clerck, 1757 syn. nov.; Araneus diadematus islandicus (Strand, 1906) = Araneus diadematus Clerck, 1757 syn. nov.; Araneus quadratus minimus Simon, 1929 = Araneus quadratus Clerck, 1757 syn. nov.; Araneus quadratus subviridis (Franganillo, 1913) = Araneus quadratus Clerck, 1757 syn. nov.; Centromerus unctus (L. Koch, 1870) = Leptorhoptrum robustum (Westring, 1851) syn. nov.; Clubiona caliginosa Simon, 1932 = Clubiona germanica Thorell, 1871 syn. nov.; Coelotes atropos anomalus Hull, 1955 = Coelotes atropos (Walckenaer, 1830) syn. nov.; Coelotes atropos silvestris Hull, 1955 = Coelotes atropos (Walckenaer, 1830) syn. nov.; Coelotes obesus Simon, 1875 = Pireneitega pyrenaea (Simon, 1870) syn. conf.; Coelotes simoni Strand, 1907 = Coelotes solitarius (L. Koch, 1868) syn. nov.; Diplocephalus semiglobosus (Westring, 1861) nomen oblitum = Entelecara congenera (O. P.-Cambridge, 1879) syn. nov.; Drassodes voigti (Bösenberg, 1899) = Scotophaeus blackwalli (Thorell, 1871) syn. conf.; Erigone decens Thorell, 1871 = Hylyphantes graminicola (Sundevall, 1830) syn. nov.; Liocranoeca striata gracilior (Kulczyński, 1898) = Liocranoeca striata (Kulczyński, 1882) syn. conf.; Phlegra rogenhoferi (Simon, 1868) = Phlegra cinereofasciata (Simon, 1868) syn. nov.; Styloctetor stativus (Simon, 1881) = Styloctetor compar (Westring, 1861) syn. nov. and comb. nov.; Tapinocyba bilacunata (L. Koch, 1881) = Silometopus incurvatus (O. P.-Cambridge, 1873) syn. nov.; Theridion varians melanotum Strand, 1907 = Theridion varians Hahn, 1833 syn. nov.; Thomisus trigonus Giebel, 1869 = Pistius truncatus (Pallas, 1772) syn. nov.; Titanoeca psammophila Wunderlich, 1993 = Titanoeca spominima (Taczanowski, 1866) syn. nov. and comb. nov.; Xysticus paniscus L. Koch, 1875 = Xysticus lineatus (Westring, 1851) syn. conf.

A surprising number of spider species listed as valid on the European checklists and databases (e.g., van Helsdingen 2014, World Spider Catalog 2015, Nentwig et al. 2015) have never been reliably rediscovered after their initial description.Most of these are probably nomina dubia, unidentifiable on the basis of the original descriptions, but to conclusively determine the status of these species, a careful examination of each individual case is necessary ( van Helsdingen 2004).The status of some of these species has been clarified as part of larger revisionary work or in isolated papers (e.g., Kronestedt 2000, van Helsdingen 2008).An extended discussion of dubious species described by Bösenberg was also provided by Braun (1982), but many cases still remain to be examined.
The Working Group "Forum and Wiki" of the Arachnologische Gesellschaft (Lemke et al. 2014) has recently started an online project documenting the information available on suspected "phantom spiders", with an initial focus on species from Central Europe.
Some of the most important collections in this context are known to be lost, including those of Menge (formerly in the Provincial Museum Gdansk, but probably lost at the end of World War II; Kraus 2009), Lebert (formerly perhaps in Zurich or Wrocław, where it could not be found; Hänggi pers.comm.) and Bösenberg (formerly in the Königliches Naturalienkabinett in Stuttgart, but destroyed during a bombing raid on September 12th, 1944;Renner 1988).In this paper, we summarize the results for a selection of species for which the type specimens have been located and examined, or where they are in all probability lost.We also synonymise a number of subspecies with their nominate form, if they were originally described as sympatric (or even syntopic) variations and thus cannot be considered as subspecies in the modern sense.More detailed supporting information, including all original descriptions and figures, is available on the associated Wiki page (http://wiki.spinnen-forum.de/index.php?title=Phantomarten).

Species accounts in alphabetical order
Aelurillus simoni (Lebert, 1877) = nomen dubium (Salticidae) The original description was based on three adult females and a male (Lebert 1877: 310, pl.6, f. 45-47; as Aelurops simoni).L. Koch, who had seen the types, stated (in Lebert 1877) that the species was new and occurred not only at the type locality in Switzerland, but also in South Tyrol (Italy).The type locality at an altitude of 1280 m indicates that this may be a montane or alpine species, such as Pellenes lapponicus (Sundevall, 1833), which shows suggestive similarities in the genitalia, but this remains speculative.Neither the illustration of the palpus, which is apparently shown in expanded state, nor the very schematic figure of the epigyne, nor the extensive description seem sufficient to allow a confident identification of this species.The type material is probably lost (see Introduction).
Agelena mengeella Strand, 1942= Allagelena gracilens (C. L. Koch, 1841) syn. conf. -syn. nov. in Bonnet (1955) (Agelenidae) This species was first described by Menge (1871: 285, pl. 52, f. 165) as Agalena brunea, matching a species similar to Allagelena gracilens to egg sacs similar to those of Agroeca brunnea (Blackwall, 1833).Strand (1942) noticed the error and proposed the new name A. mengeella; however, he did not examine the type material and was uncertain about the actual identity of the species, although he realized that it is most likely that Menge's specimens belonged to either Allagelena gracilens or Agelena labyrinthica.These two species were commonly confused at the time, but the illustrated pedipalp and epigyne both support an identification with the former, and Menge himself had already pointed out the similarity -his misidentification was apparently only based on the wrongly assigned egg sacs.Against Strand (1942), and in agreement with Bonnet (1955), we therefore conclude that even in the absence of the type material the synonymy of the two species can be established with confidence.This is also in agreement with Prószyński & Staręga (1971), who also synonymized A. brunea with A. gracilens, following the use of the name by several earlier Polish authors.
Agelena mengei Lebert, 1877 = nomen dubium (Agelenidae) Lebert's description of a female is very extensive, but does not allow an unambiguous identification (Lebert 1877: 211, pl. 6, f. 42).The most likely candidate would seem to be Agelena labyrinthica, which matches the description and illustration very well; however, Lebert reports A. labyrinthica from many locations, and insists that this specimen belongs to a different species, although the only diagnostic difference explicitly mentioned seems to be a slight variation in body proportions.Possibly the species could even be a member of Tegenaria s. lat.
Agyneta resima (L.Koch, 1881) = nomen dubium (Linyphiidae) This species was described in the genus Erigone (Koch 1881: 50, pl. 2, f. 4), which at that time included a large part of the small Linyphiidae, but the similarity with Agyneta rurestris (C.L. Koch, 1836) discussed in the original description justifies the transfer to Agyneta.A more precise identification seems, however, impossible, based on the very vague illustrations and textual description.The type material seems to be lost (not in BMNH). A. resima is one of several dubious species included by Roewer (1928) in his key of German spiders.He even added additional details on the habitat and phenology of the species, although the source of this information is unclear.The popularity and easy accessibility of Roewer's work is most likely responsible for reports of the species from Cieszyn in South Poland (Książkówna 1936), as well as for the notorious "Balkan rediscoveries" of many of the species discussed here (see Braun 1982 for details).
Amaurobius spominimus Taczanowski, 1866 = Titanoeca psammophila Wunderlich, 1993 = Titanoeca spominima (Taczanowski, 1866) syn.nov.and comb.nov.(Titanoecidae) This species was described by Taczanowski without figures and with a very short description of less than 3 lines (Taczanowski 1866: 4), and the type material appears to be lost (not in ZMW).It would thus seem an obvious candidate for being a nomen dubium.However, the short description, which is based on specimens collected in the dunes of Pragą and Dąbrowa close to Warsaw, mentions a number of distinguishing characters that allow a confident identification: "Prosoma reddish-brown; opisthosoma short, rounded, hairy, black; legs reddish-black hairy; length: female 4 mm.About 10 specimens collected in sand under a lawn of reindeer lichen (Cladonia)".Of all cribellate species in the area, only Titanoeca psammophila shares these characters (Titanoeca species were often placed in Amaurobius at the time of Taczanowski's work).T. psammophila was long confused with Titanoeca quadriguttata (Hahn, 1833), but is distinguished from this and other Central European Titanoeca species by the combination of a lack of white spots, the smaller size and the psammophilous (not titanophilous) habitat.The large number of specimens examined by Taczanowski makes it unlikely that the specimen was an unusually small or dark form of another species.Even though the description only mentions the size of a female specimen (perhaps because it was particularly large), there is no indication that only females were found, and the striking white spots of males (and most subadult males) of related species would not have escaped Taczanowski's attention.Braun (1969) had mentioned T. psammophila as a "melanistic and nanistic form" of T. quadriguttata from the Mainzer Sand (SMF 20769/15119, examined by TB).Other records are known from southern Sweden (Öland, Östergötland, Stockholm) and Finland (Åboland), from the dunes north-east of Berlin (Pimpinellenberg), from sandy meadows in the South of the Czech Republic (Hodonín area), and neighbouring regions of Slovakia (Lakšárska Nová Ves), from South Hungary (Kiskunság National Park), from the Perm Region in the easternmost part of the European part of Russia, and in Poland from Biebrza National Park, 200 km north-east of Warsaw (Kupryjanowicz 1997a, Jakobitz & Broen 2001, Gajdoš & Majzlan 2005, Esyunin 2006, Gallé & Fehér 2006, Kronestedt 2010, Hula et al. 2014).Thus, although no recent records of T. psammophila are known from the Warsaw area, the locus typicus of A. spominimus is located in the epicentre of the known distribution and consists of very typical habitat.As T. psammophila was only described quite recently and has been very rarely reported, the name is not protected by prevailing usage, and the older synonym takes priority as Titanoeca spominima.
Anyphaena accentuata obscura (Sundevall, 1831) = Anyphaena accentuata (Walckenaer, 1802) Miller, 1967 Anyphaena obscura Bösenberg, 1902(misidentification, not A. a. o. Lebert, 1877) = Anyphaena furva Miller, 1967 The name obscura was first used by Sundevall for a specimen similar to Tegenaria domestica (Sundevall 1831: 21, sub Agelena obscura), but already two years later he realized that this specimen was an old female of Anyphaena accentuata, in which the characteristic markings of the opisthosoma had been obliterated (Sundevall 1833: 265, 269).The name was later used independently by Lebert (1877: 242) for a dark variety ("Spielart") of A. accentuata, without reference to Sundevall and without the intention to establish a subspecies in the modern sense.Bertkau (in Förster & Bertkau 1883: 210) uses Lebert's name for the males of a dark species of Anyphaena found in Bonn, Germany.This species is, however, clearly distinct from A. accentuata, as can be seen from the illustration of the male pedipalp provided by Bösenberg (1902: 258, pl. 24, f. 373) based on Bertkau's material (now lost; Braun 1982).It seems very likely that these specimens actually belonged to A. furva, a rare species of Anyphaena.Although the tibial apophysis as illustrated by Bösenberg is certainly exaggerated, it is sufficiently similar to that of A. furva, which is broader and more massive ("breiter und plumper") than that of A. accentuata (Miller 1967).Also, the lack of ventral spines at the base of the pedipalpal femur, the more uniform dorsal hairs on the pedipalpal tibia, and the more cylindrical (rather than anteriorly broadened) shape of the tibia are clearly visible in comparison to the figures of A. accentuata on the same plate and match the diagnostic features of A. furva (Miller 1967).Moreover, A. furva is regularly found as almost black specimens (Bauchhenss 2009).No other European species of Anyphaena matches the description of Bertkau's specimens.Bertkau (1880: 253) had originally reported his specimens as A. sabina, but had changed his opinion after a male had been examined by Simon, and the shape of the pedipalpal tibia certainly excludes this identification.A. furva is found in xerothermic habitats and would be another example of a distinctly thermophilic element reported by Bertkau for the Bonn area.Other thermophilous species, often with Ponto-Mediterranean affinities, found by Bertkau around Bonn include, e.g., Cetonana laticeps, Sagana rutilans, Euryopis quinqueguttata, Heriaeus graminicola (sub Heriaeus hirtus in Braun 1960), Pellenes nigrociliatus, Philaeus chrysops, and Saitis barbipes (Bertkau 1880, Bösenberg 1903, Braun 1960).Therefore, his discovery of A. furva, which extends the known area of this rarely reported species by several hundred kilometres to the west, is not all that surprising.
Araneus diadematus stellatus C. L. Koch, 1836 = Araneus diadematus Clerck, 1757 syn.nov.(Araneidae) Araneus diadematus islandicus (Strand, 1906) Switzerland), but without any description.A description was only provided forty years later by Simon (1929: 683), who must therefore be regarded as the valid author of this taxon.A. q. minimus was the only named variety of A. quadratus Simon maintained in his Arachnides de France, reporting it as a local montane form, found on dwarf shrubs of alpine meadows; it is thus not a subspecies in the modern sense.Similar melanistic specimens are typical for boreoalpine populations of Araneus diadematus as well (e.g., var.islandicus Strand, 1906, andvar. stellatus C. L. Koch, 1836, both of which would not be considered subspecies in the modern sense, and have to be treated as synonyms of the nominate form).The synonymy for var.stellatus was already proposed by Thorell (1870) and Lessert (1910), but not accepted by all later authors (e.g., Simon 1929).Another montane form of Araneus quadratus was reported by Franganillo from Spain (Franganillo 1913: 127), where he found female specimens in their silken retreats "in gorse and low shrubs on the slopes of the mountains" in the surroundings of Gijón or La Guardia.From the description it is clear that this greenish form of the species ("with four strikingly visible spots") was never intended as a subspecies in the modern sense, and it was never used as such by Franganillo, who describes it as a variety only.A. quadratus has been reported as being able to actively change its colour (Bunn 1957), and the features of the epigyne ("scapus large and bent upwards, as in Epeira trifolium Hentz", referring to a lateral view of the epigyne illustrated in Emerton 1884) also seem to fall within the normal variation of A. quadratus.

Araniella silesiaca (Fickert, 1876) = nomen dubium (Araneidae)
The status of this species, which had been first described as Epeira s. based on a female specimen from the environs of Wrocław (Fickert 1876: 70), was examined in detail by Blanke (1982), who concluded that the species cannot be unambiguously recognized based on the original description.While many authors have identified the species as Araniella alpica (L.Koch, 1869), the existence of highly similar forms, including the sister species A. inconspicua (Simon, 1874), precludes a confident assignment to this species.The original types are very likely to be lost.Strand, 1910 = nomen dubium (Linyphiidae) This species was described by Strand (1910: 48) from a juvenile and poorly preserved specimen found in a cave in Franconia, Germany.The types are most likely lost (not in MfN), and even if they were rediscovered, a confident identification would be close to impossible.

Centromerus ludovici Bösenberg, 1899 = nomen dubium (Linyphiidae)
The type material of this species described by Bösenberg (1899: 115, pl. 1, f. 2) was destroyed during World War II (Renner 1988), like many of Bösenberg's types.Wunderlich (1973) and Braun (1982) consider the species as a member of what is now the genus Agyneta, but agree that a more precise identification is impossible.
Centromerus unctus (L.Koch, 1870) = Leptorhoptrum robustum (Westring, 1851) syn.nov.(Linyphiidae) The original description by Koch (1870: 24, sub Erigone uncta) already doubted the validity of this species and pointed out the close similarity to Erigone huthwaitii (O.P.-Cambridge, 1861) (= L. robustum).The mentioned diagnostic characters do not allow a discrimination from this species, and Koch mentions that any observed differences could easily be explained by the commonly observed expansion of the palpal organs.Even though the type material seems to be lost, the synonymy seems justified, considering the highly distinct male genitalia of L. robustum and the fact that it is the sole member of its monotypic genus.Simon, 1932 = Clubiona germanica Thorell, 1871 syn.nov.(Clubionidae) The name C. caliginosa was introduced by Simon (1932: 965) for the female of a species originally considered by Koch (1867: 311) as Clubiona holosericea De Geer (= Clubiona phragmitis C. L. Koch, 1843).Koch's mistake was first noticed by Thorell (1871), who redescribed the species under the new name Clubiona germanica.Simon, however, felt that the males and females illustrated by Koch did not belong to the same species and introduced another new name for the latter.The justification for this move is unsatisfactory: the (admittedly crude) illustration of the epigyne provided by Koch  The type of this species, which was described as very similar to Entelecara acuminata (Wider, 1834) and Diplocephalus picinus (Blackwall, 1841) (Westring 1861: 235; sub Erigone semiglobosa), is preserved in Thorell's collection in the NRS.It was originally kept in dried state on a pin, and transferred into alcohol by Åke Holm, who also studied the specimen and discovered the synonymy with E. congenera, as recorded on a label he added to the vial (Kronestedt pers. comm.).D. semiglobosus is the senior synonym, but it has not been used as a valid name after 1899; to our knowledge, it only occurs in general catalogues, which should be considered mere nomenclators according to article 23.9.6 of the International Code of Zoological Nomenclature.In contrast, the junior synonym E. congenera has been in general use for the last 100 years, being used by far more than 25 works by more than 10 authors in the last 50 years (for example, Miller 1971, Klomp & Teerink 1973, Locket et al. 1974, Punda 1975, Albert 1979, Bauchhenss et al. 1987, Roberts 1987, Baehr 1988, Blick & Scheidler 1991, Hauge & Hansen 1991, Heimer & Nentwig 1991, Braun 1992, Schultz 1992, Millidge 1993, Albrecht 1995, Finch 1997, Hermann 1998 Drassodes myogaster (Bertkau, 1880) = nomen dubium (Gnaphosidae) This species, described as Drassus m. based on a single female from Bonn (collected at exactly the same location as Anyphaena accentuata obscura), was repeatedly synonymized with Drassodes lapidosus (Walckenaer, 1802) (e.g., by Reimoser 1937, Grimm 1985).This is, however, dubious, considering not only the presence of the morphologically all but indistinguishable sister species D. cupreus in the same area, but also the fact that Bertkau did describe D. lapidosus in the same paper, and saw closer similarities of D. myogaster with D. pubescens, D. luteomicans (sub D. portator), D. rubidus and D. villosus.As the type material is apparently lost, no reliable identification of the species is possible.

Clubiona caliginosa
Drassodes voigti (Bösenberg, 1899) = Scotophaeus blackwalli (Thorell, 1871) syn.conf.-syn.nov. in Grimm (1985) (Gnaphosidae) The species, described as Drassus voigtii, was initially synonymized with Drassodes villosus (Thorell, 1856) (Reimoser 1937).Only the discovery of a putative female syntype (paratypoid) in Bösenberg's collection in the Zoological Museum Hamburg by Grimm (1985) revealed that the species is synonymous with Scotophaeus blackwalli.In retrospect, this matches Bösenberg's illustration of the epigyne quite well (Fig. 1), and the type locality in the inner city of Bonn also agrees with the synanthropic habits of S. blackwalli in Central Europe (Grimm 1985;Roberts 1998).Incidentally, this case illustrates that the declaration of taxa as nomina dubia will always be tentative; an initial careful revision of Bösenberg's collection by Braun (1982) failed to discover the type and concluded that D. voigti was a nomen dubium ("dubiose Art").
Euophrys striolata (C.L. Koch, 1846) = nomen dubium (Salticidae) This species, first described based on a poorly preserved female from near "Carlsbad in Böhmen", which is now Karlovy Vary in the Czech Republic (Koch 1846(Koch : 47-48, f. 1306)), is similar to Euophrys frontalis and E. terrestris.This is one of the few species described by C. L. Koch that Simon (1864) lists as "species invisa" in his revision of European Salticidae, so presumably the type was already lost by then.The description and figure do not allow an unambiguous identification, beyond the fact that this is almost certainly the synonym of a common species (Bonnet 1955).Bösenberg, 1902 = nomen dubium (Linyphiidae) Gonatium gilbum Bösenberg, 1902 = nomen dubium Gonatium pallidum Bösenberg, 1902 = nomen dubium The type material of these species was destroyed in World War II (Renner 1988).The descriptions do not allow an unambiguous identification.Despite a number of tentative identifications in the literature, an unambiguous identification is impossible in all cases (Braun 1982).All reported specimens from Eastern and Southern Europe that could be examined turned out to belong to well-known species (Braun 1982).The holotype of Erigone compar, a single dried male and pedipalp in the collection of the Naturhistoriska riksmuseet, Stockholm, was examined in 1942 by Åke Holm, who added a corresponding identification label to the specimen (Kronestedt pers. comm.).He identified the specimen as belonging to Styloctetor stativus.Westring's name is the senior synonym, and as it has been used repeatedly since 1899, due to a mistaken synonymization of G. compar and G. latebricola (sensu Simon) by Hull (1932), the older name cannot be considered as a nomen oblitum according to article 23.9 of the International Code of Zoological Nomenclature.Even though S. stativus has been very widely used in the last 100 years, and its replacement by the senior synonym will be inconvenient, it does not seem justified to appeal to the International Commission on Zoological Nomenclature requesting a ruling under the plenary power to suppress the older synonym.Thus, we suggest that Styloctetor compar (Westring, 1861) should be considered the valid name for the species.Wunderlich, 1973 = nomen dubium (Linyphiidae) This species, in contrast to most of the species discussed here, has been found again after the original description.It turned out that all specimens found were parasitized females, and it is likely that they are malformed representatives of a common species (Harvey et al. 2002) belonging in the genus Tenuiphantes.The original description emphasizes the similarity in habitus to T. mengei, but Wunderlich (2008) stated that both T. mengei and T. flavipes were common at the type locality and considered L. beckeri a nomen dubium.

Lepthyphantes thienemanni Schenkel, 1925 = nomen dubium (Linyphiidae)
The female type specimen is preserved in Schenkel's collection in the Naturhistorisches Museum Basel; however, its epigyne is missing.The description emphasises the noticeably small and pale appearance of the epigyne as the main diagnostic character.This indicates that the specimen was probably a subadult female of a widespread and common species of Lepthyphantes s. lat., especially as another four female specimens were later found in February, March and June in bogs in Northwest Germany by Peus (1928; material determined by Schenkel, but apparently lost, not in NMB).
Micrargus incomtus (O.P.-Cambridge, 1872) = nomen dubium (Linyphiidae) The type material of this species seems to be missing in the collection O. Pickard-Cambridge in the Oxford University Museum of Natural History.The description, as Erigone incomta, compares the species to Agyneta saxatilis (Blackwall, 1844) and Maso sundevalli (Westring, 1851), but the form of the pedipalp, especially the long spiral embolus exclude a closer affinity with these species and instead support a placement in Micrargus Dahl, 1886.However, the typical prosomal grooves of the males of this genus are missing in the figures and description.In the absence of type material, the species remains unidentifiable.
Microneta iracunda (O.P.-Cambridge, 1879) = nomen dubium (Linyphiidae) This species, described as Neriene iracunda, after a single male collected by Eugen Count Keyserling in "Lüvland" (present-day Latvia and Estonia), is described as being allied to Agyneta subtilis (O.P.-Cambridge, 1863), A. conigera (O. P.-Cambridge, 1863) and A. innotabilis (O. P.-Cambridge, 1863).Pickard-Cambridge was obviously quite familiar with this group, and it is very likely that the species should be placed in Agyneta.However, as the type material could not be found in the Pickard-Cambridge collection in Oxford, no reliable identification at the species level is possible.
Oedothorax insignis (Bösenberg, 1902) = nomen dubium (Linyphiidae) Originally described in Gonatium, the species was transferred to Oedothorax (Bertkau, in Förster & Bertkau, 1883) by Wunderlich (1974), based on the similarity of the epigyne to that of species such as Oedothorax retusus and Oedothorax apicatus.Braun (1982) confirms that according to the epigyne the species certainly belongs to Oedothorax, but also suggests a possible synonymy with Dismodicus elevatus, based on misidentified specimens from Romania (his reasoning in this case is not quite clear: there is no reason to assume that the Romanian specimens had been compared to authentic material).The type material was probably lost together with the other Gonatium types of Bösenberg (Renner 1988).
Oedothorax pallidus (Bösenberg, 1902) = nomen dubium (Linyphiidae) This species was originally described in Kulczynskiellum F. O. Pickard-Cambridge, 1895. Wunderlich (in Braun 1982) considered the species as belonging to Oedothorax, probably O. retusus, but Braun disagreed and suggested a possible identity with Gongylidium rufipes (Linnaeus, 1758) instead.The type material probably was lost together with most other linyphiid types of Bösenberg (Renner 1988), making a reliable identification impossible.
Oedothorax tener (Bösenberg, 1902) = nomen dubium (Linyphiidae) Another of Bösenberg's species.originally Kulczynskiellum tenerum, for which the type material is lost (Renner 1988) and an identification based on the incomplete description is impossible.Even the generic assignment is uncertain and Wunderlich (1973) suggested a possible placement in Tapinocyba Simon, 1884.Nevertheless, the species, which was illustrated by Roewer (1928), has been reported from the Balkans (Drensky 1929(Drensky , 1936)).

Pardosa bernensis (Lebert, 1877) = nomen dubium (Lycosidae)
As the type of the species Lycosa bernensis is probability lost, no unambiguous identification of this species is possible.The two most likely candidates are Acantholycosa pedestris (Simon, 1876) and Pyrenecosa rupicola (Dufour, 1821), based on the size (12 mm total length), the type locality in the Bernese limestone Alps, and the "strange" ("sonderbar") habitus of the specimen: dark black, long-legged and almost without pattern.Both A. pedestris and P. rupicola are large, almost uniformly black species from the limestone Alps.The type locality (Kandersteg, canton Bern) is at the centre of the known distribution of the alpine population of P. rupicola and too far west for A. pedestris (Buchar & Thaler 1993), but an identification based solely on a zoogeographical argument seems tenuous.The other Acantholycosa species are more distinctly coloured, while the similarly built Pardosa nigra (C.L. Koch, 1834) is described in detail by Lebert and reported from numerous localities, thus can probably be excluded as an alternative synonym.
Pardosa intermedia (Bösenberg, 1903) = nomen dubium (Lycosidae) Like many other types of Bösenberg, the material of this species, descirbed as Lycosa intermedia, was destroyed in World War II (Renner 1988).In the original description, Bösenberg remarked that the species has an intermediate position between Pardosa agrestis, Pardosa albatula, Pardosa monticola and Pardosa palustris.Given the general difficulties of identifying females of the monticola group, it is impossible to identify the species solely based on the description and figures.In particular, an identification with P. palustris proposed by Simon (in Bösenberg 1903) and Bonnet (1958) seems unlikely, given the highly characteristic epigyne of that species and the fact that Kulczyński examined the type and considered it a new species.Possibly the epigyne of the specimen was malformed due to parasitism, or the type was indeed a rare hybrid with intermediate characters (see Martin 2013 for a discussion of possible causes of genital malformations in Pardosa).Pardosa species are the most commonly known hosts of mermithid worms (Penney & Bennett 2006), and it seems likely that parasite-induced malformations are the basis for other phantom species in this genus as well.

Philodromus depriesteri Braun, 1965 = nomen dubium (Philodromidae)
This species, a member of the Philodromus aureolus group, was first described from two widely separated localities (Krimml, Austria, and Geisenheim, Germany), separated by 600 km including the German Alps.Nonetheless, despite its presumably extensive range and much increased collecting activities in the last decades, the species has never been found again since its description 50 years ago.The reason is probably that the two female types preserved in the Senckenberg Museum Frankfurt are malformed (or subadult) specimens with incompletely developed epigynes ( Jäger pers.comm.).Vulval structures very similar to those of P. depriesteri were observed in a female Philodromus of the aureolus group that turned out to be infected by a parasitic worm (Mermithidae or Nematomorpha; Fig. 2).This specimen was collected by beating the field layer of a wet meadow, together with typical specimens of Philodromus collinus.It therefore seems very likely that the unusual genitalia are the result of a parasite-induced malformation, comparable to the case of Lepthyphantes beckeri.Nematode infections have been repeatedly described in spiders (Meyer 2014 and references therein), and it has been speculated before that they might be the cause of genital malformations (Martin 2013).Braun (1965) already recognized the possibility that his types were aberrant specimens, but nonetheless decided to describe them as a new species, even though the highly unusual genital morphology (lacking receptacula and median septum, which are otherwise uniformly present and distinct in all species of the group) would require a radically divergent pedipalp structure and mating behaviour, which is inconsistent with the general conservative trends within Philodromus.Such a dramatic divergence would be particularly unexpected as Braun identifies a clear "sister species", Philodromus collinus C. L. Koch, 1835, which is highly similar in all non-genitalic characters.The reason for considering P. depriesteri as a nomen dubium, instead of a synonym of P. collinus, lies in the overall similarity of females in the aureolus group.
Philodromus dispar obscurus Lebert, 1877 = nomen dubium (Philodromidae) This form was described by Lebert (1877: 271) as a melanistic variety of P. dispar, found in the Urserental, Switzerland, at an altitude of 1500 m.Later authors either ignored this variety or considered it a synonym of the nominate form (Lessert 1910).The description of P. d. obscurus is, however, impossible to reconcile with P. dispar: the male is described as having entirely dark brown legs with black margins ("mit ganz dunkelbraunen, schwarz berandeten Beinen") and white-grey spots and a grey transverse band on the black opisthosoma.The female is even more different ("weicht besonders ab"), and is described as entirely dark, and larger and more massive than the nominate form.The alpine location suggests that Lebert may actually be describing dark specimens of Philodromus vagulus (Simon, 1875), a high-altitude species that is reasonably similar in general habitus to P. dispar and has a similarly elongated epigyne, but is darker, larger, and without distinct sexual dimorphism.However, the description is so vague and the number of remaining discrepancies so large that, in the absence of type material, it seems prudent to consider P. dispar obscurus as a nomen dubium.

Philodromus micans Menge, 1875 = nomen dubium (Philodromidae)
As for most of the species described by Menge, the type material of P. micans is probably lost (Kraus 2009).The form was originally described as a vari-ety of Philodromus aureolus, and this seems indeed the most likely identification, based on the figures in both the original description and the later re-description by Bösenberg (1902).Bertkau (1880) had already considered Philodromus micans as the male of P. aureolus.However, given that Muster & Thaler (2004) tentatively assign the male illustrated by Bösenberg to the closely related Philodromus buchari Kubcová, 2004, it seems currently impossible to unambiguously identify Menge's species.
Phlegra rogenhoferi (Simon, 1868) = Phlegra cinereofasciata (Simon, 1868) syn.nov.(Salticidae) This species was described based on a single male collected by Octavius Pickard-Cambridge in Baden (close to Vienna, Austria) during a trip through Europe and probably passed on to Eugène Simon during his subsequent visit to Paris (Pickard-Cambridge 1918).According to Kulczyński (1898) the species is very close (and possibly identical) to P. fuscipes Kulczyński, 1891, currently considered a junior synonym of P. cinereofasciata (Simon, 1868).More recently, the species was discussed by Stefania Hęciak in her unpublished PhD thesis (Hęciak, ca. 1983), based on material from "Galicia Vallombrosa" (probably in Spain or possibly Italy) in the collection of the Muséum National d'Histoire Naturelle, Paris.However, it is unlikely that this material is part of the type series of P. rogenhoferi, and it quite possibly belongs to a different species.Despite Prószyński's claim (2014) that "Simon's 1937: 12661267 remark on occurrence [in Austria and once in Landes, France] must be wrong", it is all but inconceivable that Simon, whose excellent memory was legendary (Savory 1961), would have confused material obtained from Pickard-Cambridge at the "summit meeting" of the Golden Age of arachnology.This interpretation is confirmed by the presence of a specimen from Baden in Pickard-Cambridge's collection in Oxford (vial 1744.7); it is not clear if this is the type described by Simon, but the specimen certainly belongs to the same series.Geographical arguments support the identification of P. rogenhoferi with P. cinereofasciata.The latter is the only species of Phlegra sufficiently similar to the species described by Simon occurring in the wider vicinity of the type locality.Perhaps even more importantly, the first published record for Austria we are aware of came from a xerothermic hillside in easy walking distance of Baden (just 10 km to the north of Baden city centre ;Franz & Beier 1948), and recently published Austrian locations are in the same general area, only 50 km further east (Malicky 1972).Further records come from the Pálava Protected Landscape Area, Czech Republic, less than 100 km north of Baden (Bryja et al. 2005).We therefore suggest following Kulczyński's tentative proposal and accepting P. rogenhoferi as a synonym of P. cinereofasciata s. lat.as defined by Azarkina (2003).Should P. cinereofasciata require further subdivision, P. rogenhoferi would probably have to be considered a senior synonym of P. fuscipes Kulczyński (1891).
Sitticus exiguus (Bösenberg, 1903) = nomen dubium (Salticidae) The illustrated epigyne of the only specimen of this species (Bösenberg 1903: 427, pl. 41, f. 625, sub Attus exiguus) is similar to that of Sitticus penicillatus (Simon, 1875), which Bösenberg described in the section immediately following the description of S. exiguus.However, as the type material was destroyed in World War II (Renner 1988), a reliable identification is impossible, particularly as an alternative identification with Heliophanus kochii has even been suggested, indicating the insufficiency of the original description (Braun 1982).
Tapinocyba bilacunata (L.Koch, 1881) = Silometopus incurvatus (O.P.-Cambridge, 1873) syn.nov.(Linyphiidae) This species, described in Erigone from a single male specimen found close to the current border between Germany and Poland, can be provisionally identified as a junior synonym of Silometopus incurvatus based on the characteristic prosoma shape and tibial apophysis (Fig. 3), as well as details mentioned in the text of the description, such as the long, fine spiral of the embolus.S. incurvatus is very uncommon and often found in coastal regions and sandy grasslands and heathlands (Merkens 1999, Schmidt & Melber 2004); in Germany the species seems to have its distribution centre around the type locality of T. bilacunata (Staudt 2015).The only other similar species is S. acutus Holm, 1977, which Palmgren (1976) considered as probably a mere geographical race of S. incurvatus.In fact, the pointed tibial apophysis in Koch's figure, as well as the distinct cephalic pit mentioned in the description, might argue for a synonymy with the form described by Holm.In contrast to S. incurvatus, S. acutus has never been reported from Germany, but there are records from northeast Poland (Kupryjanowicz 1997b), about 500 km from the type locality of T. bilacunata, in addition to the main distribution centre in northern Sweden, southern Finland and the Murmansk region of Russia (Holm 1977, Palmgren 1976, Tanasevitch 2007).Closer study of the distribution and relationship of the two forms, including re-examination of German and Polish material of S. incurvatus from inland and costal localities, and especially from the type locality of T. bilacunata, could therefore lead to a reassessment of the assumed synonymy.
Theridion kollari Doleschall, 1852 = nomen dubium (Theridiidae) The type of this species is lost, but Thaler & Gruber (2003) found the original illustrations by Doleschall (iconotypes) in the archives of the Naturhistorisches Museum Wien.Based on these figures they suggested identification as Enoplognatha sp.However, the figure and description would also be compatible with Steatoda bipunctata (Linnaeus, 1758), which Doleschall mentioned as a close relative.An unambiguous identification is in any case impossible.As this form was only mentioned as variety of a common species, no type was designated, and no relevant material could be traced in NSMW.Nevertheless, the short description clarifies without doubt that this form is not a subspecies in the modern sense, but merely refers to the common dark colour variant of this highly variable species.The vial with the material contains three specimens of P. truncatus (Schneider pers.comm.; Fig. 4), the species that was already considered as closely related in the original description (Giebel 1869: 367-368), which was based on a single female close to oviposition.
Walckenaeria mengei Bösenberg, 1902 = nomen dubium (Linyphiidae) Although this species is most likely a junior synonym of Walckenaeria nudipalpis (Westring, 1851), a reliable identification based on the crude illustrations and vague description seems impossible (Braun 1982), especially when considering that similar species (e.g., Walckenaeria obtusa Blackwall, 1836) occur in the same area.The type material is in all probability lost.Charitonov, 1928 = nomen dubium (Thomisidae) The name X. boesenbergi was suggested as a replacement name for X. concinnus Bösenberg, 1902(not X. concinnus Kroneberg, 1875).The type material is presumably lost (Braun 1960).Based on the brief description, it is not even possible to identify the genus of the specimen, and Braun (1982) suggests that the type was a subadult female.The type material of this species, kept in the Museum für Naturkunde in Berlin, was studied by Elke Jantscher for her revision of the genus Xysticus in Central Europe (Jantscher 2001) and unambiguously identified as belonging to X. lineatus.

Conclusion
The list of "phantom spiders" discussed in this paper is far from complete.Based on an initial count it seems likely that at least 5% of the taxa listed for Europe will turn out to be nomina dubia or synonyms of common species.Additional cases are documented on the Wiki page of the project and require further analysis of the type material.Most of the examined species so far have come from the German-speaking countries of Central Europe, and information on missing cases from other areas would be very welcome.We encourage the broader community of arachnologists to join the project and to help cleaning up the taxonomic and faunistic records.

Fig. 2 :
Fig. 2: Parasitized Philodromus female (left), collected in the Allgäu region, Bavaria, Germany, in August 2012.Its epigyne (centre, dorsal view) lacks receptacula and a fully developed median septum, just as seen in P. depriesteri, and during the genital preparation a parasitic worm (right) about 10 cm in length was detected.(Photographs courtesy of Stefan Rehfeldt)

Fig. 3 :
Fig. 3: Comparison of the illustrations of Tapinocyba bilacunata (L.Koch, 1881) in the original description (above, "5" and "5 a ") and the corresponding illustrations (below) of Silometopus incurvatus (O.P.-Cambridge, 1873).Despite their highly schematic nature, the figures in combination with the detailed description and locality data allow a provisional identification of the species.(Illustration of modern material from Norway, courtesy of Harald Løvbrekke) Thomisus trigonus Giebel, 1869 = Pistius truncatus (Pallas, 1772) syn.nov.(Thomisidae) Possible type material of this species is still preserved in Giebel's collection in the Zoological Collections of the Martin Luther University Halle, Germany.

Fig. 4 :
Fig. 4: Specimens of Thomisus trigonus in Giebel's collection in Halle, possibly including the original type (Photograph courtesy of Joachim Händel)