Opiliones (Daddy Long Legs)

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Harvestmen are arachnids belonging to the order Opiliones. As of 2006, over 6,400 species of harvestmen have been discovered worldwide, although the real number of extant species may exceed 10,000. The order Opiliones can be divided into four suborders: Cyphophthalmi, Eupnoi, Dyspnoi and Laniatores. Well-preserved fossils have been found in the 400-million year old Rhynie cherts of Scotland, which look surprisingly modern, indicating that the basic structure of the harvestmen has not changed much since then. Phylogenetic position is disputed: their closest relatives may be the mites or the Novogenuata. Although they belong to the class of arachnids, harvestmen are not spiders, which are of the order Araneae rather than the order Opiliones. In some places, harvestmen are known by the name "daddy longlegs" or "granddaddy longlegs", but this name is also used for two other unrelated arthropods: the crane fly and the cellar spider. These arachnids are known for their exceptionally long walking legs, compared to body size, although there are also short-legged species. The difference between harvestmen and spiders is that in harvestmen the two main body sections (the abdomen with ten segments and cephalothorax, or prosoma and opisthosoma) are broadly joined, so that they appear to be one oval structure; they also have no venom or silk glands. The feeding apparatus (stomotheca) differs from other arachnids in that ingestion is not restricted to liquid, but chunks of food can be taken in. The stomotheca is formed by extensions from the pedipalps and the first pair of legs. They have a single pair of eyes in the middle of their heads, oriented sideways. Many species are omnivorous, eating primarily small insects and all kinds of plant material and fungi; some are scavengers, feeding upon dead organisms, bird dung and other fecal material. This broad range is quite unusual in arachnids, which are usually pure predators. Most hunting harvestmen ambush their prey, although active hunting is also found. Because their eyes cannot form images, they use their second pair of legs as antennae to explore their environment. An urban legend claims that the harvestman is the most venomous animal in the world, but possesses fangs too short or a mouth too round and small to bite a human and therefore is not dangerous. This is untrue on several counts. None of the known species have venom glands; their chelicerae are not hollowed fangs but grasping claws that are typically very small and definitely not strong enough to break human skin. [READ THE REST OF THIS ARTICLE]





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