Andy Trowbridge / Nelson Cave Spider (Spelungula cavernicola) covered in dew, sitting on empty egg sack, Oparara River, Kahurangi National Park, Buller District, South Island, New Zealand. January.

Stephen Dalton / Cave Spider (Meta menardi) female with egg-sac, male above. UK, August.

Stephen Dalton / Cave Spider (Meta menardi) female with egg-sac. UK, August.

Stephen Dalton / Cave Spider (Meta menardi) female with egg-sac. UK, August.

Stephen Dalton / Cave Spider (Meta menardi) female with egg-sac. UK, August.

Chien Lee / Giant Crab Spider (Sparassidae) hides on the underside of a dead leaf during the day, Bau, Fairy Cave, Sarawak, Borneo, Malaysia

Chien Lee / Giant Crab Spider (Sparassidae) in a limestone cave, Gunung Mulu National Park, Malaysia

Stephen Dalton / Cave spider (Meta menardi) UK, Araneidae

Stephen Dalton / Cave spider (Meta menardi) UK, Araneidae

Stephen Dalton / Female Cave spider (Meta menardi) with egg-sac, UK

Stephen Dalton / Cave spider (Meta menardi) pair with egg-sac, UK

Stephen Dalton / Female Cave spider (Meta menardi) with egg-sac, UK

Stephen Dalton / Female Cave spider (Meta menardi) with egg-sac, UK

Inaki Relanzon / Unidentified spider with eggs in a cave, Ankarana Special Reserve, Ambilobe, North Madagascar.

Kerstin Hinze / Cave Spider (Meta merianae) in the cave Rocca Ulari, Borutta, Sardinia, Italy

Kerstin Hinze / Cave Spider (Meta merianae) in cave Rocca Ulari, Borutta, Sardinia, Italy

Jouan & Rius / Mygale tarantula spider in cave, Ankarana Special Reserve, Madagascar

Jouan & Rius / Spider in cave, Ankarana Special Reserve, Madagascar

PREMAPHOTOS / Grey house spider {Zosis geniculatus} female on web next to her eggs, in a cave, Thailand

Andrew Cooper / Cave spider with egg sac (Meta menardii) Devon UK England

Phil Chapman / Blind Ctenid cave spider using legs as antennae {Ctenidae} Mulu cave, Sarawak, Indonesia

Phil Chapman / Blind Ctenid cave spider using legs as antennae. {Ctenidae} Mulu cave, Sarawak, Indonesia

Philip Dalton / Cave Spider (Meta menardi) Somerset, UK

Andrew Cooper / Cave spider with egg sac (Meta menardii) Devon UK England

Pete Oxford / Cave dwelling spider in bat cave (Eumemophoriinae) Madagascar Ankarana Reserve

Pete Oxford / Cave dwelling spider in bat cave (Eumemophoriinae) Madagascar, Ankarana Reserve

Mark Moffett / Cave Tarantula (Hemirrhagus reddelli) observed by Peter Sprouse, Oaxaca, Mexico

Mark Moffett / Cave Tarantula with egg sac, Mexico

Chien Lee / Tailless Whip Scorpion from a limestone cave in Gunung Mulu National Park, Malaysia

Kim Taylor / Cave spider in sandstone cave, Surrey, England

Premaphotos / Malabar orb weaver spider (Nephilengys malabarensis) male squatting in the web of a giant female in a cave, Sumatra