Prosthetops wolfbergensis sp. nov. — a giant amongst the ‘ minute moss beetles’, with new data on other members of the genus (Coleoptera, Hydraenidae) Bilton, David T. Zootaxa 2013 3666 3 345 357 4MYPH Perkins & Balfour-Browne, 1994 Perkins & Balfour-Browne 1994 [151,803,1464,1490] Insecta Hydraenidae Prosthetops Animalia Coleoptera 10 355 Arthropoda species setosus   Discussion Members of the family Hydraenidaeare often colloquially termed ‘minute moss beetles’ (e.g. Jäch et al., 2008), in reference to their small adult body size; most species averaging around 2 mm. At up to 3.36 mmmaximum length from labrum to elytral apex  Ochthebius( Enicocerus) granulatusMulsantachieves the largest body size recorded in the family (Jäch et al., 2008; M.A. Jäch, pers. comm.). Although  P. wolfbergensis  sp. nov.displays a range of sizes, the largest paratypesslightly exceed  O. granulatusin length from labrum to elytral apex, and are much longer when their exposed abdominal apices are taken into account, making  P. wolfbergensis  sp. nov.the longest hydraenid described to date.   Prosthetopsspecies have been reported from a range of microhabitats, but based on both literature records (Perkins & Balfour-Browne, 1994; Perkins, 2008), and recent observations many species seem to be most commonly associated with rain filled rockpools, either on montane plateaux, or on rocky outcrops beside rivers. Whilst riverside rockpools are formed by a combination of stone and water erosion, on montane plateaux pools result solely from the chemical weathering effects of rainwater (Williams, 2006). Temporary rockpools of this nature are found in many parts of the world, including tropical Africa (McLachlan & Cantrell, 1980) and Western Australia, where they are known as gnammas (Bayly, 1992; 1997; Hendrich & Fery, 2008). Such pools are dry for much of the year, and are inhabited by an invertebrate fauna composed of a mixture of highly mobile, opportunistic species and specialists, the latter often having life history adaptations to cope with seasonal drought, such as dormant eggs, or desiccation resistant stages (McLachlan & Cantrell, 1980; Williams, 2006; Hendrich & Fery, 2008). In the larger rockpools it inhabited  P. wolfbergensis  sp. nov.co-occurred with  P. setosusand  Parasthetops nigritusPerkins & Balfour-Browne, 1994, as well as  Crenitis zimmermanniKnisch (Hydrophilidae)and  Canthyporus lateralis(Boheman)and  C. petulansGuignot (Dytiscidae). Of these species,  P. setosusand  C. lateralisappear to be associated with rockpool habitats (Perkins & Balfour-Browne, 1994; Biström & Nilsson, 2006; D T Bilton, pers. obs.); other species being generalists. Observations of P. w o l f b e rg e n s i s sp. nov.at Stadsaal cave reveal that both adults and mature larvae can be active in what were previously dry rockpools within one day of fresh rain. In this respect they resemble larvae and adults of  Ochthebius( Cobalius) lejolisiiMulsant & Rey, which can appear within 1 hour of the experimental wetting of dry supralittoral pools in SW England(D T Bilton, pers. obs.). Whilst adult beetles can potentially escape drought by dispersal to more permanent waters (which may explain some records of adult  Prosthetopsin other habitats), larvae do not have this option. Whether larvae of these insects have an ability to desiccate, as in the chironomid midge  Polypedilum vanderplankiHinton, 1951(Watanabe et al., 2002; Sakurai et al., 2008; Gusev et al., 2010), or whether they survive the dry phase using some other mechanism (e.g. retreat to damp crevices below the pan) remains unknown, however. Adults of  P. megacephalus,  P. setosusand  P. wolfbergensis  sp. nov.have also been found abundantly in running seepages over gently sloping exposed rock, which may provide similar biofilms to those present in rockpools.