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Australia's most notorious spider, the Sydney funnel-web spider, has not been known to cause any deaths since 1980. In this species, the male spider's venom is more toxic than the female's—a rarity among spiders. Amblypygi – "blunt rump" tail-less whip scorpions with front legs modified into whip-like sensory structures as long as 25cm or more (250 species) Haptopoda – extinct arachnids apparently part of the Tetrapulmonata, the group including spiders and whip scorpions (1 species)
A fossil arachnid in 100 million year old (mya) amber from Myanmar, Chimerarachne yingi, has spinnerets (to produce silk); it also has a tail, like the Palaeozoic Uraraneida, some 200 million years after other known fossils with tails. The fossil resembles the most primitive living spiders, the mesotheles. [59] [53] Taxonomy [ edit ] Eukoenenia spelaea ( Palpigradi) Kovoor, J. (1978). "Natural calcification of the prosomatic endosternite in the Phalangiidae (Arachnida:Opiliones)". Calcified Tissue Research. 26 (3): 267–269. doi: 10.1007/BF02013269. PMID 750069. S2CID 23119386. In addition to the eyes, almost all arachnids have two other types of sensory organs. The most important to most arachnids are the fine sensory hairs that cover the body and give the animal its sense of touch. These can be relatively simple, but many arachnids also possess more complex structures, called trichobothria. A spider might give Superman, the Man of Steel, a run for his money. Some silk made by orb weaver spiders rivals the tensile strength of steel. It's been suggested that the silk would be more effective than Kevlar in bulletproof vests. One problem: corralling a group of territorial spiders to produce the tough stuff. In addition, each spider produces so little silk that it wouldn't be practical to become a spider farmer.
Arachnids have a body usually divided into two parts, the prosoma ( cephalothorax or prosoma) and opisthosoma ('abdomen'), This contrasts with insects which have their body divided into three parts: head, thorax and abdomen. Mites and harvestmen bodies are less obviously divided, having the prosoma and opisthosoma fused together. The prosoma carries six pairs of appendages: the four pairs of legs, pedipalps and chelicerae. Pedipalps and chelicerae are modified in the different arachnid groups and may form spiny grasping limbs or lobster-like claws. The prosoma may also carry varying numbers of eyes. Garwood, Russell J. & Edgecombe, Gregory D. (September 2011). "Early Terrestrial Animals, Evolution, and Uncertainty". Evolution: Education and Outreach. 4 (3): 489–501. doi: 10.1007/s12052-011-0357-y. Most spiders have eight eyes. Some have no eyes and others have as many as 12 eyes. Most can detect only between light and dark, while others have well-developed vision. Experiments have demonstrated that some spiders can recognize and respond to specific shapes on television monitors. However they're equipped to see, all spiders have highly evolved systems to detect prey and danger.
a b Machado, Glauco; Pinto-da-Rocha, Ricardo & Giribet, Gonzalo (2007). Pinto-da-Rocha, Ricardo; Machado, Glauco & Giribet, Gonzalo (eds.). Harvestmen: the Biology of Opiliones. Harvard University Press. ISBN 978-0-674-02343-7. Spiders eat spiders. Females sometimes eat their mates, even while they are mating. Some spiders specialize in hunting down other species of spider and have evolved ways to grab them, even when their victims are in the center of their strongholds—their webs. ( Related: 18 Spider-Killing Spiders Discovered—And They Look Like Pelicans) Auerbach, Paul S. (2011-10-31). Wilderness Medicine E-Book: Expert Consult Premium Edition - Enhanced Online Features. Elsevier Health Sciences. ISBN 978-1-4557-3356-9.Arachnids have four pairs of legs, a pair of jaws (the chelicerae) and a second pair of appendages (the pedipalps). They do not have antennae or wings. Included in this diverse group are: Some cultures have found ways to use a spider's trap to get their own meals. In the South Pacific native people have made fishing nets from a spider's silk. People encourage nephila spiders to build webs between two bamboo stakes, which are then used for angling. Selden, Paul; Shear, William (2008). "Fossil evidence for the origin of spider spinnerets". Nature Precedings: 1. doi: 10.1038/npre.2008.2088.1. There are characteristics that are particularly important for the terrestrial lifestyle of arachnids, such as internal respiratory surfaces in the form of tracheae, or modification of the book gill into a book lung, an internal series of vascular lamellae used for gas exchange with the air. [20] While the tracheae are often individual systems of tubes, similar to those in insects, ricinuleids, pseudoscorpions, and some spiders possess sieve tracheae, in which several tubes arise in a bundle from a small chamber connected to the spiracle. This type of tracheal system has almost certainly evolved from the book lungs, and indicates that the tracheae of arachnids are not homologous with those of insects. [21]
After the plant has detected that it has indeed captured a living prey, specialized glands are activated and begin to release a mixture of acidic digestive juices to decompose the victim into compounds that are useful to the plant. Chemicals containing nitrogen, phosphorous, and sulfur, essential for the plant’s growth, become available to supplement the nutrients available from the soil. More recent phylogenomic analyses that have densely sampled both genomic datasets and morphology have supported horseshoe crabs as nested inside Arachnida, suggesting a complex history of terrestrialization. [51] [52] Morphological analyses including fossils tend to recover the Tetrapulmonata, including the extinct group the Haptopoda, [53] [54] [55] [56] [57] but recover other ordinal relationships with low support. Venus flytraps tend to live in nutrient-poor soil, which is why they rely on insects to help them survive. Ants, beetles, grasshoppers, flying insects, and even spiders are on the menu!According to urban legend, the daddy longlegs—those gangly creatures that seem to hang from corners around the house—are poisonous, but have mouths too small to bite humans. The name "daddy longlegs" is used in several countries to refer to a few different species—including harvestmen, which aren't actually spiders and have no venom—and spiders in the family Pholcidae, which are not known to have venom that affects humans. See also: Spider §Reproduction and life cycle, and Scorpion §Reproduction Courtship behavior of Thelyphonus sp.
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