Porrhomma is a genus of spiders belonging to the family Linyphiidae, commonly known as sheet weaver spiders or money spiders. These are typically small, often inconspicuous spiders found predominantly in various temperate and cold regions across the Northern Hemisphere.
Taxonomy
- Kingdom: Animalia
- Phylum: Arthropoda
- Class: Arachnida
- Order: Araneae (Spiders)
- Family: Linyphiidae (Sheet weaver spiders)
- Genus: Porrhomma Simon, 1884
Description and Characteristics Spiders of the genus Porrhomma are generally small, with most species ranging from 1.5 to 3 millimeters in body length. Like other members of the family Linyphiidae, they possess eight eyes, typically arranged in two rows. Their bodies are usually somber in coloration, ranging from brownish to blackish, and may exhibit variations in leg and cephalothorax color. They are characterized by a relatively robust build for their size. Specific morphological features on their chelicerae, palps (in males), and epigyne (in females) are crucial for accurate species identification, as many species are very similar in overall appearance. Porrhomma species construct small, often inconspicuous sheet webs close to the ground, in leaf litter, or among moss and low vegetation. These webs are used to intercept and capture small arthropod prey.
Habitat and Distribution Porrhomma species are widely distributed throughout the Holarctic region, which includes North America, Europe, and Asia. They are particularly diverse in temperate and boreal zones. Their preferred habitats are varied and often include damp, shaded environments such as leaf litter, moss, sphagnum bogs, under stones, and in low-lying vegetation. Some species are notable for inhabiting specialized environments like caves (making them troglobionts) or high-altitude alpine regions, showcasing their adaptability to challenging conditions.
Species Diversity The genus Porrhomma comprises approximately 60 to 70 described species worldwide, with new species occasionally being identified. Due to their minute size and similar superficial appearance, accurate species identification often necessitates microscopic examination of their genitalic structures. Examples of notable species include Porrhomma microphthalmum, Porrhomma convexum, and Porrhomma egeria.
Ecological Role As small predators, Porrhomma spiders play an important role in terrestrial ecosystems by contributing to the regulation of small insect and other invertebrate populations. They are an integral part of the detritivore food web, primarily preying on small arthropods found in the soil and leaf litter. Their predatory activities contribute to nutrient cycling and the overall health and balance of their respective ecosystems.