Ogre-faced Spiders: Family Deinopidae

© R. Glor © Joseph K H Koh © Glenda Crew © Iziko Museums of Cape Town

Etymology The Ogre-faced spider gets its name from its large protruding eyes and fangs that cause the spider to have an ogre-like appearance. Ogre-Faced spiders are also known as net-casting spiders, because of their ability to cast silken nets at their prey. The family name, Deinopidae, comes from the Greek words deinos, terrible, and opsis, appearance. Physical Description Dinopsis spinosus is the only species representing this family in the United States. The Ogre-faced spider has a large brown hump-like back, along with large eyes and chelicerae or fangs. It also uses its large protruding eyes to subdue prey at night. Since the spider’s eyes are so light sensitive, every night an area of membrane that is light sensitive is created and then destroyed at dawn. It has a long, slender, 20mm body with long slender legs which help it to blend in with its surroundings. The Ogre-faced spider tends to look just like sticks so it is often hard to spot. On their fourth pair of legs, the Ogre-faced has tiny thorns, which are used to its especially fine silk. Habitat Ogre-faced spiders tend to live on the underside of vegetation and lie completely hidden during the day to avoid predators and light. They lie completely outstretched on thin twigs so that they are camouflaged. Wherever there is stick-like flora and/or foliage, you can find an Ogre-faced. Web A very unique arachnid, the Ogre-faced spider spins a casting net that it throws at its prey to trap. Ogre-faced spiders use their faecal wastes as aiming spots on their nets to help them hit their prey easier. The net that it spins is intricately designed of especially strong silk to ensnare the limbs of insect prey. Each morning if the spider has not used its net, it will consume it. Its silk is especially fine and very sticky. It has support wires that it uses to climb around with, making movement much faster. Behavior The Ogre-faced spider is known for being a web-casting spider. They are typically slow moving and take their time. They hide during the day, because they have enormous eyes which make them ultra sensitive to light. Each night the spider comes out and builds an orb-web. Along with its web, the Ogre-Faced builds dozens of tiny nets out of its silk, and then uses them to catch its food, in the way a fisherman does, by casting those nets at bugs and other insects. In reproduction, the females mate and then lay their eggs in large thick brown sacs and hang them from low foliage using a silk stalk. After hanging the sacs, they then use fallen leaves to hide their eggs. Venom Though they do have venom, they are not considered to be a danger to humans, just insects. There are no records available of Ogre-faced spider bites on humans. Sources Florida’s Fabulous Spiders, Marshall & Edwards, 2001 http://www.museums.org.za/bio/spiderweb/deinopidae.htm http://www.amonline.net.au/factsheets/netcasting_spider.htm http://sciencebulletins.amnh.org/biobulletin/biobulletin/story1112.html