The Review of The genus SerboiuluS sTRasseR, 1962 (DiplopoDa: JuliDa: JuliDae), wiTh DescRipTion of a new species fRom seRbia

The Balkan millipede genus Serboiulus Strasser, 1962, is reviewed, and a new species, S. kresnik n. sp, isdescribed. The new species differs from all other congeners in a number of gonopod details. The distribution of the species of Serboiulus is mapped and discussed. A new key is provided for all four currently known serboiulid species.


INTRODUcTION
The taxonomic history of Serboiulus Strasser, 1962, began with Strasser's (1962) description of Serboiulus lucifugus Strasser, 1962, from the Prekonoška Pećina cave in eastern Serbia.Five years later, Gulička (1967) established a new subgenus with a new species, Serboiulus (Balkaniulus) spelaeophilus Gulička, 1967, from Vodna Pešt cave (Stara Planina Mountain) in Bulgaria.Strasser (1969) identified Serboiulus popovi Strasser, 1969 in the bulk of cave-dwelling julids from several caves in Bulgaria, and pointed out some differences in comparison with S. spelaeophilus.However, the same author (Strasser, 1973) reexamined S. popovi and compared it with samples from a few caves on Stara Planina Mt, as well as with Gulička's species, concluding that S. popovi represents a synonym of S. spelaeophilus (consequently synonymizing the subgenus Balkaniulus with the nominal genus Serboiulus).Further, Strasser (1971) described a new subspecies, S. lucifugus deelemani Strasser, 1971, from the Vetrena Dupka cave in eastern Serbia.Recently, Makarov et al. (2005) reanalyzed the topotypes of the Serbian Serboiulus representatives, raising both forms to the species level.
During a field trip in eastern Serbia, two of us (DŽA and SBĆ) collected an interesting specimen in one cave.careful examination showed that it represents a new form belonging to the genus Serboiulus.The present paper is an attempt to describe (after more than forty years) a new Serboiulus species, as well as to review all members of this genus based both on the available literature data and on material at our disposal, which is lodged at the Institute of Zoology, Faculty of Biology, Belgrade.The description of the new species follows a pattern proposed for typhloiulids by Strasser (1962), and for the genus Serboiulus by Makarov et al. (2005).
Diagnosis -The new species clearly differs from its congeners by the particularities in the gonopod structure, and especially by the presence of a connection between the mesomerite and the opisthomerite.
Length of midbody legs 1.36 mm.Adhesive pads present on anterior legs.First pair of legs in males hook-shaped (Fig. 4).coxa, postfemur and tibiotarsus each with one oral seta.Prefemur and femur each with two oral setae.Tips of hooks tuberculated on their inner side.Penis behind second leg-pairs, with straight lateral margins, converging in the basal third, while the two-thirds are almost parallel; with two short apical lobes (Fig. 6).

DIScUSSION
The genus Serboiulus includes blind, but more or less pigmented cavernicolous millipedes occurring in a restricted area of the Balkan Peninsula.Earlier, Strasser (1962) explained that the main division within typhloiulids sensu lato was made according to the presence or absence of a flagellum.There are two genera without flagella: Trogloiulus Manfredi, 1931 and Serboiulus.It is probable that the genus Buchneria Verhoeff, 1941 (with its stunted flagellum) represents a transitional condition.Furthermore, Strasser (1962) pointed out that another division had been made according to the presence of coxal pieces on the gonopods, the shape of the promerite and mesomerite and the presence/absence of intermediate lamellae.The structure and presence of lamellae is characteristic for the genus Typhloiulus sensu stricto.He also shared the opinion that the intermediate lamellae may be considered a vestige of an ancient and primitive coherence existing once between the opisthomerite and the mesomerite.Enghoff (1987) explained that the mesomerite in higher julids is developed as an independent branch, and that consequently a meso-opisthomeral complex is a plesiomorphic condition in relation to the 'mesomeritization' in higher julids.In the new species, the mesomerite is clearly connected with the opisthomerite and only its apical half is an independent branch.In virtually all other Serboiulus species, the mesomerite is deeply divided from the opisthomerite in the form of a free branch.At present, it is difficult to explain the mesoopisthomerite complex in new species and its phylogenetic relations in closely-related taxa, especially in light of the opinion that typhloiulids actually belong to the large tribe Leptoiulini (Mauriès et al., 1997).It is important to note as well that Makarov et al (2005) found that most of the body structures used before are actually not valid in the discrimination of at least the Serboiulus species; however, gonopod form is the most important character on which distinction of species can be based.The description of the new species strongly supports such an opinion.
The new species is distributed on Mt.Tupižnica in eastern Serbia.S. lucifugus (Fig. 11) is described in a cave on the Svrljiške Planine mountains, and S. deelemani (Fig. 10) is distributed in two caves on Mt.Vlaška Planina, both in southeastern Serbia.A much wider distribution is that of S. spelaeophilus (Map 1; Fig. 12) in numerous caves in Bulgaria, so that Vagalinski and Stoev (2007) assigned this species as an endemic of Mt.Stara Planina and the Danubian Plain.Biogeographically, the genus Serboiulus represents a carpathian and Balkan element, endemic to the Balkan Peninsula, whose evolution is probably correlated with geotectonic events in the carpatho-Balkan area in the past.