Metainae

Introduction

Metainae includes the genera Meta, Metellina, Dolichognatha, Chrysometa and Diphya (Álvarez-Padilla et al., 2009). Taxonomically, this group has proved to be the most unstable lineage within the family, and its composition has changed, sometimes considerably, across different phylogenetic analyses. Simon (1894) used the name Metinae for a group of similar composition.

Characteristics

Metaines are distinguished from other tetragnathids by the well sclerotized spermathecae and fertilization ducts; the short copulatory ducts (shorter than half the spermathecae length, which in some taxa, such as Meta menardi, are almost non existent); the wide separation of the spermathecae (more than two spermatheca diameters); and an ecto-basal cymbial process shaped as a cuticular flat outgrowth (this process can be massive in some species). All Metainae have just a single embolic apophysis, known as the "metine embolic apophysis." Similar embolic apophyses are also found in Cyrtognatha and Allende.

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Left: Web of Chrysometa alajuela. Right: Web of Dolichognatha. Images © 2006 Gustavo Hormiga

Metainae build a diversity of orbwebs. In some species, like Dolichognatha (shown on the right picture), the webs are horizontal and very dense (i.e., with many spiral turns and radii, including secondary radii). Meta species, such as M. menardi, build rather flimsy orbs, with few radii and spiral turns, despite the large size of these animals. Members of the large Neotropical genus Chrysometa build vertical orb webs with two sectors missing the sticky spiral turns and with a "telegraph line" running from the hub to a retreat.

Discussion of Phylogenetic Relationships

The Metainae cladogram presented here is based on the morphological and molecular analysis of Álvarez-Padilla at al. (2009). Metainae are more closely related to the Nanometa clade and Leucaugines than to Tetragnathinae. However, the limits of the Metainae remain unclear, as the composition of this lineage is very unstable and sensitive to different data treatments. At present this subfamily includes the genera Meta, Metellina, Dolichognatha, Chrysometa and Diphya.

References

Álvarez-Padilla F., Dimitrov D., Giribet G., Hormiga G. 2009. Phylogenetic relationships of the spider family Tetragnathidae (Araneae, Araneoidea) based on morphological and DNA sequence data. Cladistics (In press).

Simon E. 1894. Histoire naturelle des araignées. Paris, 1: 489-760.