Porrhomma convexum

Distinguished from other Linyphiidae by the combination of reduced posterior median eyes and convex carapace shape. Differs from congeneric species such as Porrhomma microphthalmum and Porrhomma eberhardi by subtle differences in eye size and genital morphology; precise identification requires examination of epigynum in females or palpal organs in males. The pale coloration and small size separate it from most surface-dwelling linyphiids in shared habitats.

Small-bodied spider with a convex carapace, as indicated by the specific epithet. Eye arrangement reduced, with posterior median eyes often minute or absent—a characteristic feature of the genus Porrhomma. Coloration typically pale to yellowish-brown, reflecting adaptation to dimly lit habitats. Body length approximately 2–3 mm. Legs relatively long and slender compared to body size.

Primarily associated with caves, mines, cellars, and other subterranean environments. Also recorded from deep leaf litter and moss in shaded, humid woodland areas. Requires stable, cool temperatures and high humidity. Often found in twilight zones of caves rather than deep aphotic regions.

Holarctic distribution: recorded from Canada, USA, Greenland, Europe (widespread), Caucasus, Russia (European and West Siberian regions), Kazakhstan, and Iran. Distribution reflects broad climatic tolerance within temperate zones but appears limited to suitable subterranean or cryptic microhabitats.

Adults have been recorded year-round in cave habitats, with peak activity likely in spring and summer in surface populations. Subterranean populations may show reduced seasonality due to stable environmental conditions.

Constructs flat sheet webs with a retreat, typical of Linyphiidae. In subterranean habitats, webs are placed on rock surfaces, cave walls, or in crevices. Activity patterns likely shifted toward nocturnal or arrhythmic behavior in permanent darkness.

Predator of small arthropods in subterranean food webs. Contributes to nutrient cycling in cave ecosystems through consumption of detritivores and other invertebrates. Serves as prey for larger cave-dwelling predators including other spiders and small vertebrates.

Occasionally encountered in cellars, mines, and artificial underground structures. No documented economic or medical importance. Presence may indicate suitable subterranean habitat conditions in environmental assessments.

• Porrhomma microphthalmumSimilar cave-dwelling congener with reduced eyes; distinguished by smaller posterior median eyes and differences in genital morphology
• Nesticus spp.Other cave-dwelling spiders with reduced eyes and pale coloration; separated by family-level characters including web structure and eye arrangement
• Lepthyphantes spp.Sympatric linyphiids with overlapping habitat use; distinguished by more prominent eyes and different abdominal patterning

• cave-dwelling
• subterranean
• Holarctic
• sheetweb spider
• troglophile

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life