Lathys Simon, 1884

Marusik, Yuri, Koponen, Seppo & Fritzén, Niclas, 2009, On two sibling Lathys species (Araneae, Dictynidae) from northern Europe, ZooKeys 16 (16), pp. 181-195 : 183-184

Lathys Simon, 1884

Lethia Menge, 1869: 249 .

Lathys Simon, 1884: 321 , nomen novum pro Lethia Menge, 1869 preoccupied by Lethia Hübner, 1816 in Lepidoptera.

Type species: Lethia varia Menge, 1869 from Prussia. It is considered a junior synonym of Ciniflo humilis Blackwall, 1855 (= Lathys h., from England). The type specimens of L. varia seem to be lost. It is unclear as to whether L. varia and L. humilis are synonyms. L. varia may also be a senior synonym of L. nielseni ( Schenkel, 1932) , the coloration and habitat data of Menge (1869) may refer to both species.

Lathys humilis is considered by several arachnologists, for example Lehtinen (1967), Thaler (1981) and Platnick (2009), to be the type species of the genus. However, Gertsch (1946) and Chamberlin and Gertsch (1958) clearly indicated that Lethia varia was the generotype, even though it is a junior synonym of L. humilis .

Lehtinen (1967) seems to have been the first to split Lathys into eight species groups. The third group was named humilis . Lehtinen (1967) included three species in this group: L. alticola (Denis, 1954) ; L. brevitibialis Denis, 1956 (still known from males only) and L. sexpustulata (Simon, 1878) and seems to have forgotten to include L. humilis in the list. It is not clear whether all three species belong to this group. One subspecies, L. humilis meridionalis (Simon, 1874) , known from Spain, France, Corsica and North Africa ( Platnick 2009) is not mentioned by Lehtinen (1967). Its status remains unclear, because it has not been studied by taxonomists in recent years. All three taxonomic entries for this species belong to Simon ( Platnick 2009). Following the removal of L. nielseni and L. annulata Bösenberg & Strand, 1906 from synonymy with L. humilis ( Thaler 1981; Ono 2003), and the recent synonymisation of L. alticola with L. sexpustulata ( Ledoux et al. 2008) the L. humilis -group now includes five species and one subspecies. Only three of these ( L. humilis , L. annulata and L. nielseni ) have been properly studied and undoubtedly belong to the humilis group.

The detailed morphology of the male palp in Lathys in general, and in its type species in particular, was unknown for a long time. There was no detailed written or illustrated description of the palpal tibia and bulbus. Thaler (1981) was the first to indicate and illustrate three tibial apophyses in Lathys humilis and L. nielseni . The structure of the bulbus in the Lathys stigmatisata -group was first studied by Marusik et al. (2006). They found that members of this group had a unique modification of the conductor, consisting of a very long upper part forming several coils over one another, a very long embolus, and a totally fixed terminal part of the conductor by the tibial apophyses and cymbium [cf. Marusik et al. (2006)]. The present study revealed that L. humilis and L. nielseni have the same conformation of the bulbus in general and the conductor in particular. As a result of this and previous studies it became possible to provide a new, revised diagnosis for the genus.

Lathys can be easily distinguished from other dictynids by the presence of three tibial apophyses, the long and coiled upper arm of the conductor, which totally covers the tegulum, and a screw-like terminal part of the conductor arrested by the tibial apophyses and the cymbium ( Figs 13, 15-17, 19 ).

Females of Lathys cannot be diagnosed so easily. In all Lathys species studied by us ( L. stigmatisata - and L. humilis -groups) the insemination ducts make a kind of loop or coil around the copulatory opening (cf. Figs 27, 30 and fig. 229b in Wiehle 1953). In addition, the epigynal fovea or the pair of copulatory openings are larger than or equal to the spermatheca or in some cases about two times smaller. The related genus Scotolathys Simon, 1884 has no loops (or coils) around the copulatory duct, and its spermatheca is much larger than its fovea (cf. Marusik et al. 2009).

Figures

Figures 13-19. Male palp of Lathys humilis (13-16 from Crimea) and L. nielseni (17-19 from Finland) 13, 17 retrolateral 14, 18 ventral 15-16, 19 patella, tibia and base of cymbium, retrolateral-dorsal, different turns 13, 15 after Marusik et al. (2009). Scale = 0.1 mm if not otherwise indicated.

Figures 26-32. Epigyne of Lathys humilis (26-27) and L. nielseni (28-32) 26, 28-29 digital photograph of epigyne, ventral 27, 30 epigyne after maceration, ventral 31-32 epigyne, dorsal 26-27 from Crimea 28, 30-31 from Finland 29 from Ural 26 after Marusik et al. (2009) 32 after Hu (1984). Scale = 0.1 mm.