Arachnologische Mitteilungen 55

Arachnologische Mitteilungen / Arachnology Letters 55: 52-56 Karlsruhe, April 2018 For a long time, dimorphic erigonid spiders were not recog- nised as such and considered separate species. Only when morph differences were small, for example in the size of the cephalic tubercle or the post-ocular sulci, were these someti- mes considered variations. Holm (1979: p. 269) wrote about Pelecopsis mengei (Simon, 1884): “The males occur in two dif- ferent forms, the one, which is the most frequent, with a high cephalic lobe and large sulcal orifice, the other with lower lobe and with much smaller orifice. … As no intermediate forms have been found and moreover, the two types of males have quite similar palpal tibiae and bulbs and are found together, the males of P. mengei seem to be dimorphic”. Similarly, Bos- mans & Abrous (1992) considered the specimens of Pelecopsis oranensis (Simon, 1884) with small and large postocular sul- ci, but having identical palpal tibiae and bulbs, as morphs of the same species. Diplocephalus marijae Bosmans, 2010 from Spain is another species occurring in two morphs (Bosmans et al. 2010). The decision to recognise species as being di- morphic is not easy or consequent. Roberts (1987) proposed Troxochrus scabriculus (Westring, 1851) and T. cirrifrons (O. Pickard-Cambridge, 1871) to be one, dimorphic species, but this is not followed in theWorld Spider Catalog (2018) where they are still considered two separate species. On the contrary, when the same author (Roberts 1987) proposed Diplocepha­ lus connatus Bertkau, 1889 and D. jacksoni (O. Pickard-Cam- bridge, 1904) to be forms of the same species, this opinion was accepted in the World Spider Catalog (2018). The best documented case of dimorph linyphiid spiders is that of Oedothorax gibbosus (Blackwall, 1841) and O. tuberosus (Blackwall, 1841) having very different cephalic tubercles and because of that considered separate species in older identifi- cation books (e.g., Locket & Millidge 1953, Wiehle 1960, Palmgren 1976). After a detailed study of the male palps of several Oedothorax species, Bosmans (1985) concluded that all palpal sclerites of O. gibbosus and O. tuberosus were comple- tely identical and the two species names were synonymized. De Keer & Maelfait (1988) provided further evidence from breeding experiments.They reared spiderlings from the same egg sac and obtained both forms. In our opinion, when palpal sclerites are identical, specimens should be treated as belon- ging to the same species. The aim of the present paper is to discuss two more cases of male dimorphism in Linyphiidae. Material and methods The material studied was collected by the authors or loaned from museum collections. Species were examined by mean of a Nikon SMZ1270 stereo microscope. Details of male palps and female epigynes were studied with an Olympus CH-2 microscope with a drawing tube. Left palps are illustrated. Male palps were detached and transferred to glycerol for examination under the microscope. Female epigynes were ex- cised using sharpened needles.These were then transferred to clove oil for examination under the microscope. Later, palps and epigynes were returned to 70% ethanol. Abbreviations: CAR-S = Personal collection of Antony Russell-Smith (UK), CPO = Personal collection of Pierre Oger (Belgium), CRB = Personal collection of Robert Bos- mans (Belgium), CSD = Personal collection of Samuel Dan- flous (France), MNHN = Muséum National d’Histoire na- turelle, Paris, France (curator: C. Rollard). A forgotten case of dimorphism Males and females of Diplocehalus cristatus (Blackwall, 1833) were first described by Blackwall (1833) from England as Walckenaeria c . Subsequently, O. Pickard-Cambridge (1875) described Erigone foraminifera Pickard-Cambridge, 1875 from France. Differences between the two species were based on differently shaped cephalic lobes. Pickard-Cambridge (1875: p. 208) stated that “ E. foraminifera is also allied to E. On two cases of male dimorphism in dwarf spiders (Araneae: Linyphiidae) Robert Bosmans & Pierre Oger doi: 10.30963/aramit5509 Abstract. Diplocephalus cristatus (Blackwall, 1833) is confirmed as a dimorphic species, having two morphs: cristatus and foraminifer . This viewwas first proposed by Georgescu (1969), but not supported in the literature. Diplocephalus foraminifer (O. Pickard-Cambridge, 1875), D. bicephalus (Simon, 1884), D. rectilobus (Simon, 1884), D. foraminifer thyrsiger (Simon, 1884) and D. arvernus (Denis, 1948) are here consi- dered junior synonyms of D. cristatus (Blackwall, 1833). Diplocephalus bicephalus belongs to the morph cristatus , D. rectilobus , D. thyrsiger and D. arvernus to the morph foraminifer . A lectotype ( ) ) is designated for Diplocephalus bicephalus Simon, 1884; the paratype female of D. bicephalus was incorrectly identified and actually belongs to Dicymbium nigrum (Blackwall, 1834). Savignia harmsi Wunderlich, 1980 is another dimorphic species, with the two strongly differing male morphs: typica and cor . Keywords: Araneae, dimorphic Linyphiidae, Diplocephalus, Savignia Zusammenfassung. Zwei Fälle von Dimorphismus bei Zwergspinnen (Araneae: Linyphiidae) Diplocephalus cristatus (Blackwall, 1833) wird als dimorphe Art bestätigt, mit zwei Formen: cristatus und foraminifer . Diese Meinung wurde erstmals von Georgescu (1969) vertreten, aber in der Literatur nicht unterstützt. Diplocephalus foraminifer (O. Pickard-Cambridge, 1875), D. bicephalus (Simon, 1884), D. rectilobus (Simon, 1884), D. foraminifer thyrsiger (Simon, 1884) und D. arvernus (Denis, 1948) werden nun als jüngere Synonyme von D. cristatus (Blackwall, 1833) betrachtet. Diplocephalus bicephalus gehört zur Form cristatus , D. rectilobus , D. thyrsiger und D. arvernus zur Form foraminifer . Ein Lectotypus ( ) ) wird für Diplocephalus bicephalus Simon, 1884 ausgewiesen; der weibliche Paratypus von D. bicepha- lus ist fehlbestimmt und gehört zur Art Dicymbium nigrum (Blackwall, 1834). Savignia harmsi Wunderlich, 1980 ist eine weitere dimorphe Art mit zwei sich deutlich unterscheidenden Männchen-Formen: typica und cor . This contribution was presented at the 30th European Congress of Arachnology, Nottingham, 2017 August 20-25 Robert BOSMANS, Terrestrial Ecology Unit, Ledeganckstraat 35, B-9000 Gent, Belgium; E-mail: rop_bosmans@telenet.be Pierre OGER, Rue du Grand Vivier 14, 4217, Waret l’Evêque, Belgium; E-mail: pierre55@skynet.be submitted 19.12.2017, accepted 19.2.2018, online 30.4.2018