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Ground spiders (family Gnaphosidae) are a massive, global family of over 2,500 species known for being fast-running, nocturnal,, hunting predators that do not build prey-capture webs. They are identified by their cylindrical, widely separated front spinnerets and often hide under rocks, logs, or in silk-lined tubular retreats during the day.
Key Facts about Ground Spiders (Gnaphosidae)
Appearance: They are usually dull-colored (black, brown, grey, reddish), ranging from small to medium size (typically less than 1/2 inch). A defining, reliable feature is their cylindrical, barrel-shaped anterior spinnerets, which are separated by about one spinneret diameter.
Hunting Method: Ground spiders are active hunters that run down their prey on the ground surface. Instead of a sticky web, they use a fast, thick, gluey, silk strand to immobilize prey.
Habitat and Behavior: They are found in diverse habitats, including grasslands, forests, and inside homes, often under debris, rocks, or in leaf litter. They are most active at night or during dawn/dusk.
Shelter: While they do not make webs to catch prey, both sexes construct tubular, silk-lined nests or retreats under stones, bark, or in crevices to hide during the day.
Venom and Bite: While they are capable of biting, they are generally not considered dangerous to humans. Their bite is often described as having no consequence, though it can cause minor discomfort, local irritation, or, rarely, tissue damage.
Diversity: With over 2,500 described species in more than 100 genera, it is the seventh largest spider family. Common genera include Gnaphosa, Drassodes, Micaria, Cesonia, and Zelotes.
Identification: They are often confused with other ground-dwelling spiders, but the distinct, prominent, forward-facing, and separated spinnerets are a key indicator.
