Porrhomma Simon, 1884

Růžička, Vlastimil, 2018, A review of the spider genus Porrhomma (Araneae, Linyphiidae), Zootaxa 4481 (1), pp. 1-75 : 10

Porrhomma Simon, 1884

Porrhomma Simon, 1884 — Simon (1884): p. 353.

Opistoxys Simon, 1884 — Simon (1884): p. 372; synonymised by Thaler (1975).

Type species: Erigone convexa Westring, 1851 .

Diagnosis. Males of the genus Porrhomma can be distinguished from other genera of the family Linyphiidae by the presence of a transparent concave border of the embolus, known as the velum.

Description. Prosoma longer than wide, opisthosoma oval. Clypeus hairy, particularly in males. Chelicerae with three promarginal teeth and four retromarginal teeth. Eyes often reduced. Femora I and II mostly with one dorsal spine, Fe I with or without prolateral spine(s). All Ti always with two dorsal spines (not repeated in descriptions). The Ti I usually with one prolateral and one retrolateral spine, Ti II with one retrolateral spine. Metatarsal spines absent (except in P. errans ). Mt I–III with trichobothrium, Mt IV without trichobothrium. Male palp with no tibial apophysis. Paracymbium hook-like. Distal suprategular apophysis is hooked and uniform in all species. Tegulum is provided with a protegulum (composed of two parts). Two linyphiid genra, viz. Bathyphantes and Porrhomma , are characterised by an embolic plate as a part of the embolic division (Millidge 1977). The embolic plate has a characteristic anterior process. The embolus is attached to the lateral side of this embolic plate. The embolus of the genus Porrhomma is characteristic by a transparent border of the concave side, called velum, and is accompanied by an embolic membrane. Epigynum is characterised by the location of the genital openings inside a well-defined, deep circular aperture. The form of the internal organs is usually seen through the integument. Vulva is composed of a pair of copulatory ducts ending by spermathecae.