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About half the potential prey that hit orb webs escape. A web has to perform three functions: No single design is best for all prey.
However, there are no consistent differences between orb webs built for use during the day and those built for use at night. In fact, there is no simple relationship between orb web design features and the prey they capture, as each orb-weaving species takes a wide range of prey.
The hubs of orb webs, where the spiders lurk, are usually above the center, as the spiders can move downwards faster than upwards.
If there is an obvious direction in which the spider can retreat to avoid its own predators, the hub is usually offset towards that direction.
Horizontal orb webs are fairly common, despite being less effective at intercepting and retaining prey and more vulnerable to damage by rain and falling debris.
Various researchers have suggested that horizontal webs offer compensating advantages, such as reduced vulnerability to wind damage; reduced visibility to prey flying upwards, because of the back-lighting from the sky; enabling oscillations to catch insects in slow horizontal flight.
However, there is no single explanation for the common use of horizontal orb webs. Spiders often attach highly visible silk bands, called decorations or stabilimenta, to their webs.
Field research suggests that webs with more decorative bands captured more prey per hour. There are several unusual variants of orb web, many of them convergently evolved, including: However, the significance of many variations is unclear.
In , Skylab 3 took two orb-web spiders into space to test their web-spinning capabilities in zero gravity. At first, both produced rather sloppy webs, but they adapted quickly.
Members of the family Theridiidae weave irregular, tangled, three-dimensional webs, popularly known as cobwebs.
There seems to be an evolutionary trend towards a reduction in the amount of sticky silk used, leading to its total absence in some species.
The construction of cobwebs is less stereotyped than that of orb-webs, and may take several days. The Linyphiidae generally make horizontal but uneven sheets, with tangles of stopping threads above.
Insects that hit the stopping threads fall onto the sheet or are shaken onto it by the spider, and are held by sticky threads on the sheet until the spider can attack from below.
Although the fossil record of spiders is considered poor,  almost species have been described from fossils. Hence Attercopus and the similar Permian arachnid Permarachne may not have been true spiders, and probably used silk for lining nests or producing egg-cases rather than for building webs.
Several Carboniferous spiders were members of the Mesothelae , a primitive group now represented only by the Liphistiidae.
Some Triassic mygalomorphs appear to be members of the family Hexathelidae , whose modern members include the notorious Sydney funnel-web spider , and their spinnerets appear adapted for building funnel-shaped webs to catch jumping insects.
Araneomorphae account for the great majority of modern spiders, including those that weave the familiar orb-shaped webs. The Jurassic and Cretaceous periods provide a large number of fossil spiders, including representatives of many modern families.
It is now agreed that spiders Araneae are monophyletic i. The cladogram on the right is based on J. Other views include proposals that: The appearance of several multi-way branchings in the tree on the right shows that there are still uncertainties about relationships between the groups involved.
Arachnids lack some features of other chelicerates, including backward-pointing mouths and gnathobases "jaw bases" at the bases of their legs;  both of these features are part of the ancestral arthropod feeding system.
Spiders are divided into two suborders, Mesothelae and Opisthothelae , of which the latter contains two infraorders, Mygalomorphae and Araneomorphae.
Nearly 46, living species of spiders order Araneae have been identified and as of grouped into about families and about 4, genera by arachnologists.
The only living members of the primitive Mesothelae are the family Liphistiidae , found only in Southeast Asia , China , and Japan.
Members of the genus Liphistius run silk " tripwires " outwards from their tunnels to help them detect approaching prey, while those of genus Heptathela do not and instead rely on their built-in vibration sensors.
The extinct families Arthrolycosidae , found in Carboniferous and Permian rocks, and Arthromygalidae , so far found only in Carboniferous rocks, have been classified as members of the Mesothelae.
The Mygalomorphae, which first appeared in the Triassic period,  are generally heavily built and hairy, with large, robust chelicerae and fangs.
However, mygalomorphs cannot produce the pirifom silk that the Araneomorphae use as instant adhesive to glue silk to surfaces or to other strands of silk, and this makes web construction more difficult for mygalomorphs.
Since mygalomorphs rarely "balloon" by using air currents for transport, their populations often form clumps.
Although spiders are widely feared, only a few species are dangerous to people. Their venom, although they rarely inject much, has resulted in 13 attributed human deaths over 50 years.
There were about reliably reported deaths from spider bites in the 20th century,  compared to about 1, from jellyfish stings.
Even when verification had occurred, details of the treatment and its effects were often lacking. Spider venoms may be a less polluting alternative to conventional pesticides , as they are deadly to insects but the great majority are harmless to vertebrates.
It may be possible to target specific pests by engineering genes for the production of spider toxins into viruses that infect species such as cotton bollworms.
Spiders can also be used as food. Arachnophobia is a specific phobia —it is the abnormal fear of spiders or anything reminiscent of spiders, such as webs or spider-like shapes.
Spiders have been the focus of stories and mythologies of various cultures for centuries. In some cultures, spiders have symbolized patience due to their hunting technique of setting webs and waiting for prey, as well as mischief and malice due to their venomous bites.
Web-spinning also caused the association of the spider with creation myths, as they seem to have the ability to produce their own worlds.
The Moche people of ancient Peru worshipped nature. From Wikipedia, the free encyclopedia. For other uses, see Spider disambiguation. Nos 1 to 14 as for dorsal aspect Cultural depictions of spiders.
Natural History Museum Bern. Kurt; Curry, Robert L. The Science of Nature. Retrieved 31 October Archived from the original PDF on Stimson; Jackson, Robert R.
In Balda, Russell P. Animal cognition in nature: Retrieved 31 October — via Google Books. The Journal of Experimental Biology.
Journal of Experimental Biology. Theridiidae and its exceptional copulatory behaviour: Oxford University Press US. Retrieved 30 April Annual Review of Entomology.
Exploitation of the Pseudomyrmex—Acacia mutualism by a predominantly vegetarian jumping spider Bagheera kiplingi. Salticidae that feed on nectar" PDF.
Retrieved 25 Mar Morphological and Behavioral Mimicry of Ants". University of California Museum of Paleontology. American Museum Novitates Behavioral Ecology and Sociobiology.
Evidence of subsociality in Latrodectus Walckenaer, Araneae, Theridiidae ". Annual Review of Ecology and Systematics. Zoological Journal of the Linnean Society.
Australian Journal of Zoology. European Journal of Entomology. Erik Tetlie; Lyall I. The Journal of Arachnology.
The fossil was originally named Eotarbus but was renamed when it was realized that a Carboniferous arachnid had already been named Eotarbus: Annual Review of Ecology, Evolution, and Systematics.
Nephila from the Middle Jurassic of China". The Burgess Shale and the Nature of History. Spiders of North America: Spiders of Southern Africa.
Bulletin of the American Museum of Natural History. Full text at "A review of the archaeid spiders and their relatives" PDF. Agricultural Research Council of New Zealand.
Archived from the original on Biology of Spiders 2nd ed. Illinois Department of Public Health. Sicariidae and no envenomations in a Kansas home: Journal of Medical Entomology.
Department of Entomology, Virginia Tech. Australian Venom Research Unit. American Journal of Tropical Medicine and Hygiene. Venomous and Poisonous Marine Animals: A Medical and Biological Handbook.
Western Journal of Medicine. National Science Foundation US. Journal of Ethnobiology and Ethnomedicine. Nature Reviews Drug Discovery.
British Journal of Urology International. There are many common phobias, but surprisingly, the most common phobia is arachnophobia.
Arachnophobia, or fear of spiders, is one of the most common specific phobias. Probably the most recognized of the 10 most common phobias, arachnophobia is the fear of spiders.
An Introduction to the Study of Mind. Tales, Rumors, and Gossip: Exploring Contemporary Folk Literature in Grades 7— Gods, Demons and Symbols of Ancient Mesopotamia: The British Museum Press.
The Harps that Once: Sumerian Poetry in Translation. Newcastle upon Tyne, England: The Cambridge Classical Journal. The Book of Symbols. Papers from the American Anthropologist.
University of Nebraska Press. A Culture of Peru. The Spirit of Ancient Peru: Thames and Hudson , Forest Spiders of South East Asia: With a Revision of the Sac and Ground Spiders.
Invertebrate Zoology 7th ed. Bilger, Burkhard 5 March The World of Spiders. The Life of the Spider. The Book of the Spider: From Arachnophobia to the Love of Spiders.
Main, Barbara York Spiders in Ecological Webs. Cambridge studies in ecology. Actinopodidae mouse spiders and relatives Antrodiaetidae folding trapdoor spiders Atracidae Australian funnel-web spiders Atypidae atypical tarantulas or purseweb spiders Barychelidae brushed trapdoor spiders Ctenizidae cork-lid trapdoor spiders Cyrtaucheniidae wafer trapdoor spiders Dipluridae funnel-web tarantulas Euctenizidae Halonoproctidae Hexathelidae funnel-webs or venomous funnel-web tarantulas Idiopidae Macrothelidae Mecicobothriidae dwarf tarantulas Microstigmatidae Migidae tree trapdoor spiders Nemesiidae funnel-web tarantulas Paratropididae bald-legged spiders Porrhothelidae Theraphosidae true tarantulas.
Archaeidae pelican spiders Austrochilidae Caponiidae Diguetidae coneweb spiders Drymusidae false violin spiders Dysderidae woodlouse hunters Filistatidae crevice weaver spiders Gradungulidae large-clawed spiders Huttoniidae Hypochilidae lampshade spiders Leptonetidae Mecysmaucheniidae Ochyroceratidae midget ground weavers Oonopidae goblin spiders Orsolobidae Pacullidae Palpimanidae palp-footed spiders Periegopidae Pholcidae cellar spiders Plectreuridae Scytodidae spitting spiders Segestriidae tube-dwelling spiders Sicariidae violin spiders, assassin spiders Stenochilidae Telemidae long-legged cave spiders Tetrablemmidae armored spiders Trogloraptoridae Trogloraptor marchingtoni.
List of families of spiders Spider taxonomy List of spider common names Bold are families with more than species. Ballooning Behavior Cannibalism Evolution Classification.
Araneomorphae Mesothelae Mygalomorphae Opisthothelae List of families of spiders Lists of spider species. Arachnophobia Cultural depictions Spider bite Spider fighting.
Spider web Web decorations. Portal Kingdom Animalia Phylum: Opiliones harvestmen Scorpiones scorpions. Pseudoscorpionida pseudoscorpions Solifugae camel spiders.
Amblypygi tailless whip scorpions. Schizomida shorttailed whipscorpions Thelyphonida vinegaroons. Opilioacariformes Holothyrida Ixodida ticks Mesostigmata.
Classification is based on Shultz Items in green are possibly paraphyletic groups. Retrieved from " https: Views Read View source View history.
The residual buttermilk goes on to further processing. At a later stage these packages are broken down into home-consumption sized packs. The product left after the cream is removed is called skim, or skimmed, milk.
To make a consumable liquid a portion of cream is returned to the skim milk to make low fat milk semi-skimmed for human consumption. By varying the amount of cream returned, producers can make a variety of low-fat milks to suit their local market.
Whole milk is also made by adding cream back to the skim to form a standardized product. Other products, such as calcium , vitamin D , and flavouring, are also added to appeal to consumers.
Casein is the predominant phosphoprotein found in fresh milk. It has a very wide range of uses from being a filler for human foods, such as in ice cream , to the manufacture of products such as fabric , adhesives , and plastics.
Cheese is another product made from milk. Whole milk is reacted to form curds that can be compressed, processed and stored to form cheese.
In countries where milk is legally allowed to be processed without pasteurization , a wide range of cheeses can be made using the bacteria found naturally in the milk.
In most other countries, the range of cheeses is smaller and the use of artificial cheese curing is greater. Whey is also the byproduct of this process.
Some people with lactose intolerance are surprisingly able to eat certain types of cheese. This is because some traditionally made hard cheeses , and soft ripened cheeses may create less reaction than the equivalent amount of milk because of the processes involved.
Fermentation and higher fat content contribute to lesser amounts of lactose. In addition, the aging methods of traditional cheeses sometimes over two years reduce their lactose content to practically nothing.
Ageing of some cheeses is governed by regulations;  in other cases there is no quantitative indication of degree of ageing and concomitant lactose reduction, and lactose content is not usually indicated on labels.
In earlier times, whey or milk serum was considered to be a waste product and it was, mostly, fed to pigs as a convenient means of disposal.
Beginning about , and mostly since about , lactose and many other products, mainly food additives, are made from both casein and cheese whey.
Yogurt or yoghurt making is a process similar to cheese making, only the process is arrested before the curd becomes very hard.
Milk is also processed by various drying processes into powders. Whole milk, skim milk, buttermilk, and whey products are dried into a powder form and used for human and animal consumption.
The main difference between production of powders for human or for animal consumption is in the protection of the process and the product from contamination.
Kumis is produced commercially in Central Asia. Originally, milking and processing took place on the dairy farm itself. Later, cream was separated from the milk by machine on the farm, and transported to a factory to be made into butter.
The skim milk was fed to pigs. This allowed for the high cost of transport taking the smallest volume high-value product , primitive trucks and the poor quality of roads.
Only farms close to factories could afford to take whole milk, which was essential for cheesemaking in industrial quantities, to them.
These proved impractical for transport by road or rail, and so the milk churn was introduced, based on the tall conical shape of the butter churn.
Later large railway containers, such as the British Railway Milk Tank Wagon were introduced, enabling the transport of larger quantities of milk, and over longer distances.
The development of refrigeration and better road transport, in the late s, has meant that most farmers milk their cows and only temporarily store the milk in large refrigerated bulk tanks , from where it is later transported by truck to central processing facilities.
Milking machines are used to harvest milk from cows when manual milking becomes inefficient or labour-intensive. One early model was patented in It is made up of a claw, four teatcups, Shells and rubber liners long milk tube, long pulsation tube, and a pulsator.
The claw is an assembly that connects the short pulse tubes and short milk tubes from the teatcups to the long pulse tube and long milk tube.
Cluster assembly Claws are commonly made of stainless steel or plastic or both. Teatcups are composed of a rigid outer shell stainless steel or plastic that holds a soft inner liner or inflation.
Transparent sections in the shell may allow viewing of liner collapse and milk flow. The annular space between the shell and liner is called the pulse chamber.
Milking machines work in a way that is different from hand milking or calf suckling. Continuous vacuum is applied inside the soft liner to massage milk from the teat by creating a pressure difference across the teat canal or opening at the end of the teat.
Vacuum also helps keep the machine attached to the cow. The vacuum applied to the teat causes congestion of teat tissues accumulation of blood and other fluids.
Atmospheric air is admitted into the pulsation chamber about once per second the pulsation rate to allow the liner to collapse around the end of teat and relieve congestion in the teat tissue.
The ratio of the time that the liner is open milking phase and closed rest phase is called the pulsation ratio. The four streams of milk from the teatcups are usually combined in the claw and transported to the milkline, or the collection bucket usually sized to the output of one cow in a single milk hose.
Milk is then transported manually in buckets or with a combination of airflow and mechanical pump to a central storage vat or bulk tank.
Milk is refrigerated on the farm in most countries either by passing through a heat-exchanger or in the bulk tank, or both. The photo to the right shows a bucket milking system with the stainless steel bucket visible on the far side of the cow.
The two rigid stainless steel teatcup shells applied to the front two quarters of the udder are visible. The top of the flexible liner is visible at the top of the shells as are the short milk tubes and short pulsation tubes extending from the bottom of the shells to the claw.
The bottom of the claw is transparent to allow observation of milk flow. When milking is completed the vacuum to the milking unit is shut off and the teatcups are removed.
Milking machines keep the milk enclosed and safe from external contamination. Milk contact surfaces must comply with regulations requiring food-grade materials typically stainless steel and special plastics and rubber compounds and are easily cleaned.
Most milking machines are powered by electricity but, in case of electrical failure, there can be an alternative means of motive power, often an internal combustion engine , for the vacuum and milk pumps.
This type of milking facility was the first development, after open-paddock milking, for many farmers. The building was a long, narrow, lean-to shed that was open along one long side.
The cows were held in a yard at the open side and when they were about to be milked they were positioned in one of the bails stalls. Usually the cows were restrained in the bail with a breech chain and a rope to restrain the outer back leg.
The cow could not move about excessively and the milker could expect not to be kicked or trampled while sitting on a three-legged stool and milking into a bucket.
When each cow was finished she backed out into the yard again. The milking equipment was much as today, a vacuum from a pump, pulsators, a claw-piece with pipes leading to the four shells and liners that stimulate and suck the milk from the teat.
The milk went into churns, via a cooler. As herd sizes increased a door was set into the front of each bail so that when the milking was done for any cow the milker could, after undoing the leg-rope and with a remote link, open the door and allow her to exit to the pasture.
The door was closed, the next cow walked into the bail and was secured. When milking machines were introduced bails were set in pairs so that a cow was being milked in one paired bail while the other could be prepared for milking.
This is the same as for Swingover Milking Parlours as described below except that the cups are loaded on the udder from the side. As herd numbers increased it was easier to double-up the cup-sets and milk both cows simultaneously than to increase the number of bails.
About 50 cows an hour can be milked in a shed with 8 bails by one person. Using the same teat cups for successive cows has the danger of transmitting infection, mastitis, from one cow to another.
Some farmers have devised their own ways to disinfect the clusters between cows. After washing the udder and teats the cups of the milking machine are applied to the cows, from the rear of their hind legs, on both sides of the working area.
Large herringbone sheds can milk up to cows efficiently with two people. Swingover parlours are the same as herringbone parlours except they have only one set of milking cups to be shared between the two rows of cows, as one side is being milked the cows on the other side are moved out and replaced with unmilked ones.
The advantage of this system is that it is less costly to equip, however it operates at slightly better than half-speed and one would not normally try to milk more than about cows with one person.
Rotary milking sheds also known as Rotary milking parlor consist of a turntable with about 12 to individual stalls for cows around the outer edge.
The turntable is turned by an electric-motor drive at a rate that one turn is the time for a cow to be milked completely. As an empty stall passes the entrance a cow steps on, facing the center, and rotates with the turntable.
The next cow moves into the next vacant stall and so on. The operator, or milker, cleans the teats, attaches the cups and does any other feeding or whatever husbanding operations that are necessary.
Cows are milked as the platform rotates. The milker, or an automatic device, removes the milking machine cups and the cow backs out and leaves at an exit just before the entrance.
The rotary system is capable of milking very large herds—over a thousand cows. Current automatic milking sheds use the voluntary milking VM method. These allow the cows to voluntarily present themselves for milking at any time of the day or night, although repeat visits may be limited by the farmer through computer software.
A robot arm is used to clean teats and apply milking equipment, while automated gates direct cow traffic, eliminating the need for the farmer to be present during the process.
The entire process is computer controlled. Each bail might have a box into which such feed is delivered as the cow arrives so that she is eating while being milked.
A computer can read the eartag of each animal to ration the correct individual supplement. The holding yard at the entrance of the shed is important as a means of keeping cows moving into the shed.
Most yards have a powered gate that ensures that the cows are kept close to the shed. Water is a vital commodity on a dairy farm: Pumps and reservoirs are common at milking facilities.
Water can be warmed by heat transfer with milk. From there it is pumped by a mechanical pump and cooled by a heat exchanger.
The milk is then stored in a large vat, or bulk tank , which is usually refrigerated until collection for processing. In countries where cows are grazed outside year-round, there is little waste disposal to deal with.
The most concentrated waste is at the milking shed, where the animal waste may be liquefied during the water-washing process or left in a more solid form, either to be returned to be used on farm ground as organic fertilizer.
In the associated milk processing factories, most of the waste is washing water that is treated, usually by composting, and spread on farm fields in either liquid or solid form.
This is much different from half a century ago, when the main products were butter, cheese and casein, and the rest of the milk had to be disposed of as waste sometimes as animal feed.
In dairy-intensive areas, various methods have been proposed for disposing of large quantities of milk. Large application rates of milk onto land, or disposing in a hole, is problematic as the residue from the decomposing milk will block the soil pores and thereby reduce the water infiltration rate through the soil profile.
As recovery of this effect can take time, any land-based application needs to be well managed and considered.
Dairy products manufactured under unsanitary or unsuitable conditions have an increased chance of containing bacteria.
Proper sanitation practices help to reduce the rate of bacterial contamination, and pasteurization greatly decreases the amount of contaminated milk that reaches the consumer.
Many countries have required government oversight and regulations regarding dairy production, including requirements for pasteurization.
A portion of the population,  including many vegans and Jains , object to dairy production as unethical, cruel to animals, and environmentally deleterious.
They do not consume dairy products. They state that cattle suffer under conditions employed by the dairy industry. In , it was found that bovine somatotropin BST or bovine growth hormone would increase the yield of milk.
Several pharmaceutical companies developed commercial rBST products and they have been approved for use in the US, Mexico, Brazil, India, Russia, and at least ten others.
The World Health Organization, and others have stated that dairy products and meat from BST-treated cows are safe for human consumption.
From Wikipedia, the free encyclopedia. For other uses, see Dairy disambiguation.