Meta, C. L. KOCH, 1836

Álvarez-Padilla, Fernando & Hormiga, Gustavo, 2011, Morphological and phylogenetic atlas of the orb-weaving spider family Tetragnathidae (Araneae: Araneoidea), Zoological Journal of the Linnean Society 162 (4), pp. 713-879 : 773-775

META C. L. KOCH, 1836 ( FIGS 1D , 4C , 56–60 )

Type species: Meta menardi Latreille, 1804 . The type specimens of Aranea menardi are lost ( Levi, 1980).

Diagnosis: Meta species can be distinguished from all other tetragnathid genera by the following combination of characters: abdomen as high as long ( Fig. 1D ; Levi, 1980: figs 113–115); PMS anterior surface with more than 20 aciniform spigots ( Fig. 56C ); epigynum ventrally projected with the copulatory openings posteriorly orientated ( Fig. 58A, B ); fertilization ducts crossing over the spermathecae ( Figs 58C–F , 60C ); cymbial ectobasal process and cymbial ectomedian process present ( Fig. 59A ); cymbial ectobasal process formed by a massive cuticular fold and cymbial ectomedian process shorter than half the cymbial width without macrosetae ( Fig. 59A–F ); and by having the metaine embolic apophysis, when present, fused to the embolus base ( Fig. 60A, B ).

Description: Female: body length c. 14.0 mm. Cephalic fovea formed by two deep longitudinal pits ( Fig. 57A ). Ocular area lower than the carapace lateral margins ( Fig. 57B, D ). Labium trapezoidal, wider than long and rebordered. Sternum as wide as long ( Fig. 57C ). Anterior surface of chelicerae smooth, boss present ( Fig. 57B, D ). Secondary eyes with canoe-shaped tapetum ( Levi, 1980: figs 122, 123). Eyes roughly subequal in size, lateral eyes slightly smaller and juxtaposed and on a tubercle ( Fig. 57A, B, D ). Clypeus c. 1.5 times the AME diameter. Booklung cuticle grooved. Tracheal spiracle near the spinnerets ( Fig. 56A ). ALS piriform spigots base rounded ( Fig. 56B ). PLS with more than 20 aciniform spigots; distal end of the aggregate spigots embracing the tip of the flagelliform spigot ( Fig. 56D ; Hormiga et al., 1995: fig. 19A–D). Epigynal plate protruded, copulatory openings posteriorly orientated and in the shape of longitudinal grooves ( Fig. 58A, B ). Spermathecae walls well sclerotized ( Fig. 58C–F ). Cuticle of copulatory ducts well sclerotized and shorter than half the spermathecae ( Figs 58F , 60C ). Wiehle (1967) proposed that M. menardi had a semi-entelegyne reproductive system, lacking fertilization ducts and, as in haplogyne reproductive systems, that the sperm must pass through the copulatory ducts to fertilize the eggs. Levi (1980: 40) mentioned that he could not verify that M. menardi lacked fertilization ducts, but did not state that this species had them. We found by means of SEM that M. menardi indeed has fertilization ducts; furthermore, these ducts cross over the spermathecae and copulatory duct junction ( Fig. 58D–F ). Owing to this particular configuration it is difficult to differentiate both ducts in cleared epigyna ( Fig. 60C ). Accessory glands distributed over the spermathecae, with gland openings arranged in groups ( Fig. 58E ).

Male: body length c. 10.0 mm. Cephalothorax morphology as in females, except that the anterior cheliceral cuticle is rugose ( Fig. 57B, F ). Abdomen cylindrical. PLS triplet reduced to nubbins ( Fig. 56E ). Epiandrous fusules dispersed over a flat plate and immersed in pits ( Fig. 56F ). Palpal patella with one macroseta; palpal tibia slightly longer than wide. Tegulum wider than long and slightly larger than the subtegulum ( Fig. 60B ). Conductor well sclerotized and fused to the tegulum ( Fig. 60A ). Embolic apophysis bearing several processes. Embolus short and well sclerotized ( Figs 59B , 60A, B ). Sperm duct with fewer than two switchbacks ( Fig. 60B ).

Natural history: Meta includes 37 species with a Holarctic distribution ( Platnick, 2009). Meta menardi builds vertical webs with open hubs, few radii, and few spirals (fewer than 15) ( Fig. 4C ). These spiders are usually found inside caves, near the entrance or deep inside, and in humid dark places such as tunnels, mines, and wells ( Levi, 1980). The egg-sac is white, large, drop-shaped, and hangs from a thread near the web ( Comstock, 1948; Levi, 1980). Meta menardi is the only species in which the biology is relatively well documented ( Ecker & Moritz, 1992). The web building behaviour of M. menardi was described by Eberhard (1982). Some studies of this species have covered aspects of its diet and predatory behaviour ( Yoshida & Shinkai, 1993; Smithers, 1996, 2005a), its distribution within its habitat ( Smithers, 1995), and observations on its dispersal biology and early life stages ( Smithers, 2005b; Smithers & Smith, 1998).

Taxonomy: North American Meta and some European and Japanese species have been revised ( Levi, 1980; Marusik, 1986; Yaginuma, 1986; Marusik & Koponen, 1992). Our description and diagnosis are based on the species included in Levi (1980), Marusik & Koponen (1992), and the illustrations of Roberts (1985) of the European species. We coded M. menardi for the phylogenetic analysis, by far the species that has been most intensively studied. We propose that Meta and Metellina are different genera, as suggested by previous authors ( Palmgren, 1978a; Levi, 1980; Coddington, 1990a; Marusik & Koponen, 1992). However, this hypothesis has not been cladistically tested with a sufficiently large taxonomic sample of both genera. The phylogenetic analysis that has included more Meta species to date included only Meta nigridorsalis Tanikawa, 1994 and M. reticuloides Yaginuma, 1958 ( Tanikawa, 2001: fig. 141B). This latter author proposed five synapomorphies for the genus Meta : male chelicerae larger than female chelicerae; large teeth on the chelicera fang furrow; sperm duct with switch backs; paracymbium large and modified; and epigynum weakly sclerotized ( Tanikawa, 2001). Other phylogenetic analyses have found Meta as sister either to a clade comprised by Metellina and Chrysometa ( Hormiga et al., 1995) or to a clade including Dolichognatha and Metellina ( Álvarez-Padilla, 2007) . The morphology plus behaviour data set recovered Meta as sister to a clade that includes Metellina and Dolichognatha ; when these data were combined with DNA sequences Meta came out as sister to a clade that includes the previous taxa plus Chrysometa and Diphya ( Fig. 144 ).

Figures

Figure 1. Examples of tetragnathid spiders: A, Tetragnatha versicolor from Virginia, USA (voucher number DSCN7721, see Appendix 2 detailed locality data). B, Tetragnatha sp. from Daintree National Park, Australia (DSCN1180). C and E, Leucauge venusta from Virginia, USA (DSCN3055). D, Meta menardi from Zealand, Denmark (photograph by Nikolaj Scharff).

Figure 4. Webs of tetragnathids: A, Mesida argentiopunctata from Noosa National Park, Australia (37 cm horizontal) (Leuc004b). B, Metabus ebanoverde from Ébano Verde Natural Reserve, Dominican Republic (72 cm horizontal) (DSCN7567). C, Meta menardi from Zealand, Denmark (15 cm horizontal, photograph by Nikolaj Scharff). D, Metleucauge eldorado from California, USA (40 cm horizontal). E, Mollemeta edwardsi from Puyehue National Park, Chile (50 cm horizontal). F, Nanometa sp. from Lamington National Park, Australia (18 cm horizontal) (DSCN0492). Photographs (D) and (E) by Gustavo Hormiga.

Figure 56. Meta menardi abdomen: A, tracheal spiracle and colulus. B, anterior lateral spinnerets. C, posterior median spinnerets. D, female posterior lateral spinnerets. E, male posterior lateral spinnerets. F, epiandrous fusules. Images (A–D) from SEMFAP042, (E–F) from SEMFAP076.

Figure 57. Meta menardi cephalothorax: A, female dorsal view. B, male tangential view. C, female sternum. D, female tangential view. E, female chelicera. F, male chelicera. Images from female specimens SEMFAP042, from male SEM- FAP076.

Figure 58. Meta menardi epigynum: A, lateral view. B, posterior view. C, dorsal view. D–F, spermatheca and ducts view. All images from SEMFAP042.

Figure 59. Meta menardi male pedipalp: A, ventral view. B, apical view. C, dorsal view. D, embolic division. E, ectal view. F, cymbial ectobasal process and paracymbium. All images from SEMFAP076.

Figure 60. Meta menardi genital anatomy illustrations: A, male pedipalp expanded. B, pedipalp bulb cleared ventral view. C, cleared epigynum dorsal view.

Figure 144. Preferred optimal cladogram from the study of Álvarez-Padilla et al. (2009). This tree is based on a combined analysis, using direct optimization methods, of multigene DNA sequences and the morphological and behavioural data set presented in Appendix 2. The single most parsimonious tree was 54 536 steps when all the data were analysed simultaneously. Numbers under each node correspond to the node numbers in Table 1 where all support values are plotted and the synapomorphies mapped.