Cave Spider

Cave spiders, genus Meta, are large-eyed orb weavers in the family Tetragnathidae specially adapted to life at the entrances and twilight zones of caves, mines, and similar underground spaces. Although they do not live in total darkness, they are strongly associated with these humid, sheltered environments, where light levels are low but not entirely absent.

One of the best-known species, Meta menardi, has a wide distribution across parts of Europe and beyond, where it is a familiar sight to cavers spotting its large, round-bodied form resting motionless near the cave mouth or suspended in a web strung across a passage. Its legs and body tend to be proportionally long and its eyes relatively large, features that assist movement and prey detection in the dim conditions it favors.

A particularly striking feature of cave spider biology is the way females suspend their egg sacs on long silk threads from the cave ceiling, sometimes many at a time in a single chamber, creating a distinctive hanging cluster that is one of the clearest signs of the species' presence.

• Large, rounded abdomen, often patterned with mottled brown or tan markings
• Long, slender legs relative to body size, useful for navigating uneven cave surfaces
• Large eyes adapted for low-light conditions near cave entrances
• Web is a large, orb-shaped structure often strung across a cave passage or entrance
• Egg sacs are distinctive, teardrop-shaped, and suspended individually on long silk threads from the ceiling
• Lookalikes include other large orb weavers, but the cave-associated habitat and hanging egg sacs are strong identifying clues

Cave spiders occupy the twilight zone of caves, mines, tunnels, culverts, and similar humid, sheltered underground spaces, generally avoiding total darkness deep within a cave system. They are found across parts of Europe and other temperate regions with suitable karst or mine habitat, and adults can be encountered year-round given the stable temperature and humidity of most cave environments.

Cave spiders build large orb webs across passageways or near entrances to intercept flying insects that move in and out of the cave, including moths, flies, and other insects sheltering in or passing through the space. During periods of inactivity they often rest motionless on the cave wall or ceiling, relying on their cryptic coloration for concealment. Within cave ecosystems, they represent an important predator, and their egg sacs and prey remains contribute organic material to the otherwise nutrient-poor cave environment.

Females produce distinctive teardrop-shaped egg sacs, which they suspend individually from long silk threads attached to the cave ceiling, often positioning several in the same general area. Spiderlings emerge and disperse within the cave system or move toward the entrance zone to establish their own webs, growing through a series of molts. Development can take one to two years depending on local conditions, with the stable cave climate allowing activity throughout much of the year.