Tropes

Livescience_2013 02805.txt

#Funnel-web Spiders: Families, Bites & Other Facts Funnel-web spiders are spiders that build funnel-shaped webs which they use as burrows or to trap prey. Three distinct spider families are known popularly as funnel-web spiders. Spiders in the Agelenidae Dipluridae and Hexathelidae families all build funnel-shaped webs but that is where their similarities end. Agelenidae spiders also called funnel weavers live throughout the world including North america. They build funnel-shaped webs between two braces such as branches or grass blades. In general their bites are not harmful to humans. A possible exception is the hobo spider but scientists are extremely unsure if this species is poisonous or not. Hexathelidae spiders live in Australia and their funnel webs are lined really burrows with silk These spiders have a dangerous bite. Two well-known species of Hexathelidae are the Sydney funnel spider and the northern tree funnel spider; both are shortlisted often for the Most Deadly Spider in the World title. Spiders in the Dipluridae family are commonly known as funnel-web tarantulas. Their funnel webs are rather messy. Most of these spiders live in the tropics of Central and South america but they are found worldwide including Australia Africa and Central asia. There are more than 1200 species of agelenids found worldwide. About 100 are in North america. Members of one North american genus Agelenopsis are referred commonly to as grass spiders. Appearance Agelenids are sized medium for arachnids about 4 to 20 millimeters long. They are usually grey or brown with spots on their backs and banded legs. Their eight eyes are arranged in two rows. Behavior Like most species of spiders funnel weavers are nocturnal. They are known to flee from light. They typically live for less than a year dying in the cold weather. In warmer places they can live for two years. Males spend most of their time wandering in search of a mate though they usually die after they mate a few times. Females rarely leave their webs. They typically lay several egg sacs and cover them in webbing for protection. Funnel spiders lay eggs in the fall and the spiderlings hatch in the spring. Dead female spiders are often found clinging to the egg sac. Web Residents of grassy areas will recognize the funnel webs scattered in the grass during the summer and early fall. Webs are seen also often in the corners of porches or in the cracks of shingles (anywhere there is a crevice for them to build a funnel web inside). Prey don t get caught in the funnel which functions as a retreat for the spider to hide in while it waits for prey to come. Instead prey gets caught in a large sheet web that surrounds the funnel s entrance. Depending on the species the sheet web may or may not be sticky but either way prey gets caught in its slippery or sticky surface. The spider calmly waits calmly in its funnel until it feels the sheet web vibrate as prey gets caught in it. The spider which has no problem walking on the web then runs out and bites its victim. In Europe and North america in the 17th and 18th centuries their webs were used often for bandages. These spiders typically eat insects though they have been known to eat other spiders. There are about 40 species of hexathelidae in Australia and while not all of them are poisonous the Sydney funnel spider and the tree-dwelling venomous biters have garnered deadly reputations in the Land Down Under. Appearance These funnel spiders are sized medium getting up to about one inch and are typically black or brown. They are distinguished by their shiny carapace (hard covering over the front of the body) which is haired lightly. Males are smaller than females. Behavior These mostly nocturnal spiders can be found at any time of the year. They prefer humid climates as they are susceptible to drying out. During the summer males leave their burrows and go wandering for females. The two spiders spar until the female accepts the male. To mate they rear up on their hind legs and press their bodies together. They also assume this rearing position when threatened. The female spider lays her eggs in her burrow. Once they hatch the young spiders stay in the burrow until they are big enough to leave. Males only live for a few months after mating but females can live for several years (some reports say up to 20). Burrowers Funnel spiders pick moist and sheltered places to build their burrows like under rocks or logs or in shrubbery. The entrance to the burrow is surrounded by irregular strands of silk which act as trip wires alerting the spider hiding in the burrow that prey is present. The spider then goes out and attacks. These spiders usually eat insects or small vertebrates like lizards or frogs. Tree dwellers While most funnel spiders live on the ground a few species on the eastern coast of Australia live in wet forest trees. They typically live in rotting holes in the bark and build silk trip wires outside the holes to alert themselves to prey. The inside of their holes may be lined with silk and bits of bark are used to disguise the entrance. Their dwellings have been found as much as 30 meters off the ground. Dangerous species All species of Australian funnel-web spiders are considered dangerous but the two most notorious are the Sydney funnel-web spider and the northern tree-dwelling funnel spider. The black or brown Sydney funnel-web spider s habitat correlates closely with the greater Sydney area. Male Sydney funnel-webs are exclusively responsible for human deaths from this spider's bite. Their venom is five times as toxic as the female s because it contains a special chemical called Robustoxin. Females lack this chemical. Furthermore males wander searching for mates and running a higher risk of encountering humans while females stay in their burrows. The northern tree-dwelling funnel spider is also highly dangerous but much more rarely encountered because it lives in a remote mountain area. Antivenom was discovered in the 1980s and no one has died of bites from either species since n

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