Join arachnologist Hannah Wood as she talks about her field expeditions to Madagascar and other remote places in the world. They may be small, but assassin spiders are among the most dangerous spiders on the planet –- if you're another spider, that is. A classic example of convergent evolution, Wood's findings suggest that the need to strike out at prey from a distance encouraged the evolution of extended spider body parts on more than one occasion.
Hannah M.Wood is an arachnologist with the California Academy of Sciences; University of California, Berkeley (Ph.D.), Graduate Assistant.
Arachnologist Hannah Wood introduces the "stealthy predator" of the world of arachnids: the assassin spider. With its unusually long neck, the assassin spider actively hunts its only prey -- other spiders.
Any member of the class Arachnida, primarily carnivorous arthropods having a well-developed head, a hard external skeleton, and four pairs of walking legs. Spiders and scorpions have a segmented body, but daddy longlegs, ticks, and mites do not. Arachnids range in size from tiny mites (0.003 in. [0.08 mm] long) to the 8-in. (21-cm) black scorpion of Africa. As arachnids grow, they molt several times (seemolting). Most are unable to digest food internally; instead, they inject their prey with digestive fluids and suck the liquefied remains. Arachnids are found worldwide in nearly every habitat. Most groups are free-living, but some mites and ticks are parasitic and can carry serious diseases of animals and humans. Venomous spiders and scorpions also may pose a danger to humans. However, most arachnids are harmless and prey on insect pests.
Any of approximately 38,000 predatory arachnid species, mostly terrestrial, in the order Araneida, abundant worldwide except in Antarctica. Spiders have two main body parts, eight legs, two pincerlike venomous appendages, and three pairs of spinnerets. Species range in length from 0.5 to about 90 mm (0.02 to 3.5 inches). The venom of a few species (e.g., brown recluse) is harmful to humans. Most species catch insect prey in a web of silk extruded from the spinnerets. Spiders change little during growth, except in size. Species are classified largely on the basis of the number and arrangement of eyes and the type of web. See alsoblack widow; tarantula; wolf spider.