Leucaugines

Introduction

Leucaugines are a very species-rich group which includes some of the most beautiful tetragnathid spiders. Many leucaugines are relatively large and have vivid colors and reflective silvery abdominal patterns. Leucaugines are most diverse in the tropics but some genera have representatives in the temperate zones. Some leucaugines are very common and well known, such as the orchard spider (Leucauge venusta), a species widely distributed in the Americas.

The subfamily Leucauginae was created by Caporiacco (1955) to include four Leucauge species from Venezuela. Leucaugines have traditionally been included within the “metine’’ tetragnathid lineages.

Characteristics

All leucaugines have two rows of long feathered trichobothria on the leg femora which often can be seen with the naked eye. Males are usually almost the same size as females and, unlike in other tetragnathids, cheliceral sexual dimorphism is not conspicuous. In addition, the male pedipalps of leucaugines have a dorso-basal cymbial process and a mesally displaced tegulum. The embolus has a large base, at least twice longer than wide, and the sperm duct path is complex with more than two coils.

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Left: Tylorida sp. © 2006 Gustavo Hormiga Right: Leucauge venusta. © 2008 Chuck

Most leucaugines build two-dimensional orb-webs that can vary considerably in the number of spiral turns and radii even between individuals of the same species. In some Leucauge species the webs have a tree dimensional barrier structure.

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Leucauge venusta webs. © 2007 Gustavo Hormiga

Discussion of Phylogenetic Relationships

Several cladistic analyses have corroborated the monophyly of leucaugines (Álvarez-Padilla, 2007; Álvarez-Padilla et al., 2009; Dimitrov and Hormiga, 2009; Tanikawa, 2001). The tree presented here is based on the morphological and molecular analysis of Álvarez-Padilla et al. (2009).

The following tetragnathid genera have at lest some of the synapomorphies of Leucauginae (but not have been included in any analyses): Alcimosphenus, Atelidea, Mecynometa, Okileucauge, Opas and Pickardinella. These genera are listed here as incertae sedis.

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).

Álvarez-Padilla F. 2007. Systematics of the spider genus Metabus O. P.-Cambridge, 1899 (Araneoidea: Tetragnathidae) with additions to the tetragnathid fauna of Chile and comments on the phylogeny of Tetragnathidae. Zool. J. Linn. Soc. 150: 285–335.

Caporiacco L.di. 1955. Estudios sobre los arácnidos de Venezuela. 2a parte: Araneae. Acta Biol. Venez. 1: 265–448.

Dimitrov D., Hormiga G. 2009. Revision and cladistic analysis of the orbweaving spider genus Cyrtognatha Keyserling, 1881 (Araneae, Tetragnathidae). Bulletin of the American Museum of Natural History 317: 1-139.

Tanikawa A. 2001. Okileucauge sasakii, a new genus and species of spider from Okinawajima Island, southwest Japan (Araneae, Tetragnathidae). J. Arachnol. 29: 16–20.