Tmeticus Menge, 1868

Marusik, Yuri M. & Koponen, Seppo, 2010, A review of the Holarctic genus Tmeticus Menge, 1868 (Araneae, Linyphiidae), with a description of a new genus, ZooKeys 59, pp. 15-37 : 15-16

Tmeticus Menge, 1868

Type species.

Tmeticus leptocaulis Menge, 1868 (= Tmeticus affinis (Blackwall, 1855)).

Diagnosis.

Males of this genus are easily recognized by possessing a mastidion (large tooth on frontal part of chelicera) and by their elongate palp with patella longer than cymbium, ventral terminal tooth on patella, and thin bulbus (as wide as terminal part of tibia). Females are recognized by their flat epigyne without a cavity. Males may be confused only with the trans-Palaearctic Hylyphantes graminicola (Sundevall, 1830) because it also has a mastidion and a patellar tooth. However, the males of Hylyphantes have shorter palp, undivided embolic division and screw-like embolus.

The females of Tmeticus may be confused with those of several genera, such as Oedothorax Bertkau, 1883 or with Donacochara speciosa (Thorell, 1875). However, Oedothorax females have a different colour pattern, and Donacochara speciosa is notably larger.

Description.

Small to medium-sized (2.5-4.1), light to dark-coloured erigonines. Male carapace unmodified and without sulci, it may be uniformly coloured or with a darker cephalic region. Abdomen unmodified, dark, of uniform colour. Male chelicera modified by possessing a mastidion (Ma, promarginal tooth). Maxilla with apical-retrolateral spine. Tibial spines 2-2-1-1. TmIV present. TmI 0.65-0.8. Male palp elongate. Femur, patella and tibia longer than wide. Patella with conical, ventral terminal tooth (Tt). Tibia with two apophyses (Ta). Paracymbium large, with or without ( Tmeticus affinis ) distinct apical pocket. Tegulum with distinct sac (Ts) and large ( Tmeticus tolli ) or small protegulum (Pt). Radix with straight apical process (Ap), tailpiece (Tp) without extension, embolus (Em) short and straight, or long and forming a semicircle; embolic membrane (Me) large. Epigyne without distinct fovea or openings. Median (=dorsal, sensu Hormiga 2002) plate plain or with ridges.

Composition.

According to Platnick’s (2010) catalogue eight species are listed in this genus: Tmeticus affinis (Blackwall, 1855) (Holarctic), Tmeticus bipunctis ( Bösenberg & Strand, 1906) (Far East Asia), Tmeticus neserigonoides Saito & Ono, 2001 (Japan), Tmeticus nigerrimus Saito & Ono, 2001 (Japan), Tmeticus nigriceps ( Kulczyński, 1916) (Northern Siberia), Tmeticus ornatus (Emerton, 1914) (USA & Canada), Tmeticus tolli Kulczyński, 1908 (Siberia) and Tmeticus vulcanicus Saito & Ono, 2001 (Japan). In fact, there are three more species names within this genus: Tmeticus difficilis Kulczyński, 1926, Tmeticus dubius Kulczyński, 1926 and Gongylidium vile Kulczyński, 1885. Of these, the first two are listed under Centromerus , and the last one under Oedothorax . These three names were included in Tmeticus by Holm (1973) and Eskov (1994) but were considered as synonyms of Tmeticus tolli .

On the basis of the present study, we conclude that Tmeticus encompasses four species: Tmeticus affinis , Tmeticus nigriceps , Tmeticus ornatus and Tmeticus tolli . A new genus has been erected for Tmeticus bipunctis . Tmeticus neserigonoides might be correctly placed in this genus, but as we failed to re-examine its specimens, we treat it as incertae sedis (see below). Two other Japanese species belong elsewhere, but their correct assignments require further study.

Comments.

Tmeticus is unusual in the Erigoninae because all its species can be recognized by their carapace colour pattern. Three sibling species: Tmeticus nigriceps , Tmeticus ornatus and Tmeticus tolli cannot be recognized by their embolic division, but the females of these species have distinctly different epigynes.

Interrelationships.

Tmeticus affinis differs from the three other species by the shape of the paracymbium, the straight embolus and the high protegulum with papillae. It also possesses a different type of the tibial apophysis, not originating at the terminal edge of the tibia as in other Erigoninae and other Tmeticus , but slightly aside of the edge.

Relationships.

In general appearance, male palp structure and cheliceral dentition, the members of this genus are similar to Hylyphantes graminicola , but the latter has a different type of embolic division and epigyne. When Wiehle (1956) described Donacochara speciosa (Thorell, 1875) he compared it with Tmeticus affinis . Both species have a long palp, small bulbus, and the chelicera of the male has a mastidion. The embolic division in both species is rather similar, but the radical process and the embolus proper occupy different positions.

The embolic division of Tmeticus is similar to those in Phaulothrix hardyi (Blackwall, 1850) (cf. Millidge 1977: f. 18), Lophomma punctatum (Blackwall, 1841)(Fig. 58) or members of Oreoneta Chyzer & Kulczyński, 1894 (Fig. 57). All these genera have a more or less straight, two-armed embolic division (embolus proper + anterior radical process), with the embolus proper situated more dorsally than the process. All three genera have a wide embolic membrane.

Millidge (1977) placed Tmeticus in a separate nominative group with Ostearius Hull, 1911, Donacochara Simon, 1884, Eboria Falconer, 1910 and Sciastes Bishop & Crosby, 1938. Hormiga (2002) placed Tmeticus close to a very heterogeneous group of the higher Erigoninae that includes such unrelated genera (in terms of the structure of the embolic division) as Walckenaeria Blackwall, 1833 (twisted radix), Oedothorax , Entelecara Simon, 1884, Gonatium Menge, 1968 and others.

Judging from the drawings (Figs 35.110, 35.111 in Draney and Buckle 2005), Tmeticus can be related to the Nearctic Nanavia monticola Chamberlin & Ivie, 1933. The latter species seems to have been mistakenly considered a synonym of Leptorhoptrum robustum (Westring, 1851) (see Platnick 2010). Both genera and species were synonymized by Eskov and Marusik (1994) on the basis of a comparison of Leptorhoptrum robustum and the poor figures of Nanavia monticola . Nanavia monticola has a very long palpal tibia, and the paracymbium and embolic division are very similar to those of Tmeticus affinis . The relationships of the two genera and taxonomic status of Nanavia Chamberlin & Ivie, 1933 are outside the scope of this study and will be considered elsewhere.

Key to Tmeticus species

The males of Tmeticus nigriceps and Tmeticus ornatus cannot be distinguished.