Wikiversity

Speeders Temporal range: Pennsylvanian – Holocene, 319–0 Ma PreЄ Є O S D C P T J K Pg N
An assortment of different spiders.
Scientific classification
Kinrick:	Animalia
Phylum:	Arthropoda
Subphylum:	Chelicerata
Cless:	Arachnida
Order:	Araneae Clerck, 1757
Suborders
Mesothelae Opisthothelae
Diversity[1]
113 faimilies, c. 46,000 species

Spiders (order Araneae) (kent as ettercaps, attercaps or nettercaps an aa) are air-braithin arthropods that hae aicht legs an chelicerae wi fangs that inject venom. Thay are the lairgest order o arachnids an rank seivent in tot species diversity amang aw ither orders o organisms.^[2] Speeders are foond warldwide on ivery continent except for Antarcticae, an hae acome established in nearly ivery habitat wi the exceptions o air an sea colonisation. As o November 2015, at least 45,700 speeder speshies, an 113 faimilies hae been recordit bi taxonomists.^[1] Houiver, thare haes been dissension within the scienteefic commonty as tae hou aw thir faimilies shoud be clessifee'd, as evidenced bi the ower 20 different clessifications that hae been proponed syne 1900.^[3]

Anatomically, speeders differ frae ither arthropods in that the uisual bouk segments are fused intae twa tagmata, the cephalothorax an abdomen, an jyned bi a smaw, cylindrical pedicel. Unlik insects, speeders dae nae have antennae. In aw except the maist primitive group, the Mesothelae, speeders hae the maist centralised nervish seestems o aw arthropods, as aw their ganglia are fused intae ane mass in the cephalothorax. Unlik maist arthropods, speeders hae na extensor muscles in thair limms an insteid extend them bi hydraulic pressur.

Thair abdomens beir appendages that hae been modifee'd intae spinnerets that extrude silk frae up tae sax teeps o glands. Speeder wabs vary widely in size, shape an the amoont o sticky threid uised. It nou appears that the spiral orb wab mey be ane o the earliest forms, an speeders that produce tangled cobwabs are mair abundant an diverse nor orb-wab speeders. Speeder-lik arachnids wi silk-producin spigots appeared in the Devonian period aboot 386 million years aby, but thir ainimals apparently lackit spinnerets. True speeders hae been foond in Carboniferous rocks frae 318 tae 299 million years aby, an are verra seemilar tae the maist primitive survivin suborder, the Mesothelae. The main groups o modren spiders, Mygalomorphae an Araneomorphae, first appeared in the Triassic period, afore 200 million years aby.

A yerbivorous speshies, Bagheera kiplingi, wis descrived in 2008,^[4] but aw ither kent speshies are predators, maistly preyin on insects an on ither speeders, awtho a few lairge species an aa tak birds an lizards. It is estimait that the warld's 25 million tons o speeders kill 400–800 million tons o prey per year.^[5] Speeders uise a wide range o strategies tae captur prey: trappin it in sticky wabs, lassoin it wi sticky bolas, meemickin the prey tae avoid detection, or runnin it doun. Maist detect prey mainly bi sensin vibrations, but the active hunters hae acute veesion, an hunters o the genus Portia shaw signs o intelligence in thair choice o tactics an abeelity tae develop new anes. Speeders' guts are too narrae tae tak solits, an thay liquefee thair fuid bi fluidin it wi digeestive enzymes. Thay an aa grind fuid wi the bases o thair pedipalps, as arachnids dae nae hae the mandibles that crustaceans an insects hae.

Male spiders identifee themsels bi a variety o complex coortship rituals tae avoid bein eaten bi the females. Males o maist species survive a few matins, leemitit mainly bi thair short life spans. Females weave silk egg-cases, ilk o that mey conteen hunders o eggs. Females o mony speshies care for their young, for ensaumple bi cairyin them aroond or bi sharin fuid wi them. A minority o species are social, biggin communal wabs that mey hoose anywhaur frae a few tae 50,000 individuals. Social behaviour ranges frae precarious toleration, as in the weedae speeders, tae co-operative huntin an fuid-sharin. Awtho maist speeders leeve for at maist twa year, tarantulas an ither mygalomorph speeders can leeve up tae 25 years in capteevity.

While the venom o a few species is dangerous tae humans, scientists are nou resairchin the uise o speeder venom in medicine an as non-pollutin pesticides. Speeder silk provides a combination o lichtness, strenth an elasticity that is superior tae that o synthetic materials, an speeder silk genes hae been insertit intae mammals an plants tae see if thir can be uised as silk factories. As a result o their wide range o behaviours, speeders hae acome common seembols in airt an meethologie seembolisin various combinations o patience, cruelty an creautive pouers. An abnormal fear o speeders is cried arachnophobia.