LinEpigThe problemLinyphiidae is the most speciose spider family in the nearctic region, with the bulk of diversity represented by the Erigoninae (about 650 species). The outwardly drab females have often received cursory treatment in descriptions. Female erigonines they are the only spiders in North America that lack a key to genus. Our limited ability to identify erigonine material hampers studies of diversity and distribution.

An online resource on erigonine epigyna Nina Sandlin, Field Museum

The projectLinEpig is a project to make images of erigonine epigyna available online. The relatively two-dimensional epigynal plates typical of this group make it possible to provide reference images adequate, in most cases, for distinguishing among closely related species using single-shot, uncomposited photos. I image the external genitalia of specimens reliably identified by linyphiid specialists, using a stereoscopic microscope with a digital camera attachment. Specimens are immobilized in fine sand or electrophoresis beads for positioning. The liquid is chilled to minimize shifting of the minute specimens due to Brownian motion as the alcohol is heated by the light source. Additional shots are taken across a depth-of-field range to allow substitution of higher-quality composite images at a later date. A habitus image is provided to the Nearctic Spider Database. Collection data is recorded in a Darwin Core 2 data set as used by GBIF.

TaxonomyMost erigonine genera lack modern revisions. Of of about 117 nearctic genera, 33 are monotypic, and 15 are ditypic. Paucity of identification tools slows taxonomic progress by preventing synonymies and new species from being discerned. Erigoninae is taken sensu lato following Draney & Buckle 2005 and Hormiga 2000, thus encompassing several genera (Eularia, Scironis, Sisicus) which exhibit the erigonine characters of minute size (< 2 mm) and flat epigynal plates without prominent scape. LinEpig uses tagging and commenting to annotate recent synonymies and species-placement issues, to complement existing taxonomic e-resources not able to present alternative interpretations.

Acknowledgements and thanks to» Dr. Michael Draney, University of Wisconsin-Green Bay » Dr. Paula Cushing, Denver Museum of Nature & cience » Rod Crawford, Burke Museum, University of Washington » Dr. Richard A Bradley, Ohio State University» Dr. Robert L Edwards » RS Vetter, University of California, Riverside » Dr.Sandra L. Brantley, Museum of Southwestern Biology» David Shorthouse, Nearctic Spider Database

TOOLS

Q-Color digital camera

Olympus SZX10 stereoscope

Very small glasswareLinEpig main page

LinEpig detail page showing taxonomic annotations

LinEpig habitus images at Nearctic Spider Database

Seven specimens of Islandia unicornis in a 1-dram vial

Ceraticelus fissiceps, Paquin & Dupérré , 2005

Ceraticelus vesperus, Chamberlin & Ivie, 1939

(one example)

Ceraticelus fissiceps egigynum Ceraticelus vesperus epigynum

Ceraticelus fissiceps habitus (female)

Ceraticelus vesperus habitus (female)

Notes

Erigonines are small. The females are often poorly illustrated, and they lack a key.