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

publication ID

http://dx.doi.org/10.3897/zookeys.59.508

publication LSID

lsid:zoobank.org:pub:0D722BFB-48E1-43BB-81F3-7CF5AF2894CE

persistent identifier

http://treatment.plazi.org/id/4FE5144D-5B03-5D02-D849-7C058D42A752

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scientific name

Tmeticus Menge, 1868
status

 

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.