Only Half of All Spiders Have Been Discovered

Female Mexican red-kneed tarantula (Brachypelma smithi) / George Chernilevsky via Wikimedia
Janet Fang 08 Dec 2014, 23:15

Only half of all spiders have been discovered. And that’s an optimistic estimate. 

So far, scientists have identified more than 44,500 spider species on six continents (sorry, Antarctica). And there may be at least as many still out there waiting to be discovered, according to curator emeritus Norman Platnick of the American Museum of Natural History (AMNH) in New York. "Because these are only estimates, people disagree," he told Live Science in 2012. (The number was about 43,000 back then.) "I have argued that we are basically halfway through. Some of my colleagues think I am being way too optimistic and we are closer to only 20 percent through." 

In order to estimate the number that remain to be discovered, researchers often utilize museum collections. Because finding and collecting a spider from the field takes much less work than figuring out what it is, collections often accumulate unidentified specimens, Platnick explains. He also heads one of the Planetary Biodiversity Inventory projects, which aims to complete global revisions of major organism groups over the next few years. He’s focusing on goblin spiders (family Oonopidae). When the project began, only 500 of these small spiders had been discovered, and researchers think the actual number is closer to 2,500. 

Just last month, the museum wrapped up their biennial “Spiders Alive!” exhibit, which featured live arachnids representing 20 species, from goliath bird eaters and fish hunters to orb weavers and a scorpion or two. 

Around 2,000 scorpion species have been described, and up to three times that number remains to be discovered. "I say that because whenever we go to an area, let's say in the southwestern United States or South Africa or Australia that are relatively better known for scorpion fauna, and we survey the area thoroughly and using a variety of modern techniques we double or triple the number of species in the area,” scorpion expert Lorenzo Prendini of the AMNH told Live Science. That means there may be up to 7,000 species of these claw-wielding, stinging arachnids on the planet. 

For comparison, there are about 5,400 known mammal species.

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