Metabus O.Pickard-Cambridge 1899
Creators: name: Álvarez-Padilla, Fernando
name: Hormiga, Gustavo
Publisher: name: Zenodo
Year: 2011
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Araneae
Tetragnathidae
Metabus

description: METABUS O. P.- CAMBRIDGE 1899 (FIGS 4B, 61–65)   
 Type species: Metabus ocellatus (Keyserling, 1864). The syntype series of Tetragnatha ocellata consists of two males and seven females from Bogota (Colombia), deposited at the Natural History Museum, London (examined).   
 Diagnosis: Metabus species can be distinguished from all other tetragnathid genera by the following combination of characters: leg I more than four times the body length; femur IV without trichobothria (Fig. 62C); epigynum flat, well sclerotized and with a rectangular atrium (Fig. 63A, B); spermathecae weakly sclerotized (Figs 63C, 65C); fertilization ducts coiled over the copulatory ducts (Fig. 63B); CEDP longer than half the cymbial width and parallel to the cymbium longitudinal axis; conductor longer than wide and apically projected (Fig. 64B).   
 Description: Female: body length c. 14.0 mm. Cephalothorax fovea formed by two short transverse grooves (Fig. 62A). Ocular area lower than carapace lateral margins (Fig. 62F). Labium trapezoidal, wider than long and rebordered. Sternum longer than wide (Fig. 62G). Anterior surface of chelicerae smooth; boss present (Fig. 62E). Secondary eyes with canoe-shaped tapetum. Eyes subequal in size, lateral eyes slightly smaller, juxtaposed, and on a tubercle. Clypeus more than one AME diameter high. Abdomen covered with silver guanine patches. Booklung cuticle smooth (Fig. 61B). Tracheal spiracle near the spinnerets, almost without accessory glands (Fig. 61F). Median tracheae not ramified, with leaf-shaped tips and shorter than half the lateral tracheae length (Fig. 61C–E). ALS with c. 70 piriform spigots. PMS with three aciniform spigots between the cylindrical and minor ampullate silk gland spigots but without any aciniform spigots over the anterior surface. PLS with c. 20 aciniform spigots roughly arranged in two parallel lines; distal end of the aggregate spigots embracing the distal end of the flagelliform spigot (Álvarez-Padilla, 2007: fig. 9A–C). Epigynal plate flat (Fig. 63A, B). Copulatory openings ventrally orientated with the shape of longitudinal grooves located under the atrial edges (Fig. 65C). Spermathecae walls weakly sclerotized. Copulatory ducts more than half the spermathecae length but less than its total length, cuticle weakly sclerotized. Fertilization ducts well sclerotized, coiled around copulatory ducts (Figs 63C–E and 65C). Accessory glands ducts in individual pits, concentrated over spermatheca-fertilization duct junction (Fig. 63C, F).   
 Male: size and somatic morphology similar to that of the female, except that legs I and II are considerably longer. Epiandrous plate well sclerotized, fusules immersed in a transverse groove with bases wider than fusule shaft. Posterior margin of the epiandrous plate thicker than the anterior margin (Fig. 61G). PLS triplet reduced to nubbins (Álvarez-Padilla, 2007: fig. 9D). Male palpal patella with one macroseta. Paracymbium hook-shaped, without apophyses and considerably shorter than cymbium length (Fig. 64A). Tegulum roughly ovoid, with an ectal depression produced by the displaced subtegulum (Fig. 64B). Conductor rigid, with sclerotized edges, although some parts are weakly sclerotized. Conductor-tegulum attachment membranous, originating at the ventral edge of the tegulum (Fig. 65A, B). Embolus base rectangular, longer than wide (Fig. 65A). Embolus flexible and weakly sclerotized. Sperm duct path convoluted, with several coils (Fig. 65D).   
 Natural history: This genus includes four species with a Neotropical distribution. Metabus ebanoverde Álvarez-Padilla, 2007, builds horizontal webs with open hubs, fewer than ten radii, and fewer than 20 spirals (Fig. 4B), but other Metabus species seem to have denser webs (Lopardo et al., 2004: fig. 16). Metabus ocellatus (Keyserling, 1864) builds communal orb webs over ponds and shares a communal retreat during the night (Buskirk, 1975a: fig. 1, 1986; Uetz & Craig, 1997). This communal behaviour has not been reported for any other species in the family. The web building behaviour of M. ocellatus was described by Eberhard (1982). The communal behaviour of M. ocellatus has been described and discussed by Buskirk (1975b).   
 Taxonomy: Metabus has recently been revised and its monophyly tested (Álvarez-Padilla, 2007). Synapomorphies for Metabus include the conductor apex curved apically and the absence of trichobothria on the fourth femora. In that study Metabus was sister to a clade that included L. venusta and L. argyra (Álvarez-Padilla, 2007: fig. 9B). Okileucauge Tanikawa, 2001 species are very similar to Metabus in their genital anatomy and somatic morphology, i.e. both genera lack femoral trichobothria. However, a previous phylogenetic analysis proposed that Metabus and Okileucauge were not sister taxa; instead Metabus was hypothesized to be sister to a clade that included Leucauge, Okileucauge, Tylorida, and Mesida (Tanikawa, 2001; Fig. 8B). The morphology plus behaviour data set did not resolve Metabus sister taxa relationships with either Tylorida or Orsinome (Fig. 143A). When these data are combined with DNA sequences Metabus come out as sister to a clade that includes Orsinome and Tylorida (Fig. 144).
description: Published as part of Álvarez-Padilla, Fernando & Hormiga, Gustavo, 2011, Morphological and phylogenetic atlas of the orb-weaving spider family Tetragnathidae (Araneae: Araneoidea), pp. 713-879 in Zoological Journal of the Linnean Society 162 (4) on pages 776-779, DOI: 10.1111/j.1096-3642.2011.00692.x, http://zenodo.org/record/5440885