Editing Chelicerata (section)

===Senses===
As with other arthropods, chelicerates' [[cuticle]]s would block out information about the outside world, except that they are penetrated by many sensors or connections from sensors to the nervous system. In fact, spiders and other arthropods have modified their cuticles into elaborate arrays of sensors. Various touch and vibration sensors, mostly bristles called [[seta]]e, respond to different levels of force, from strong contact to very weak air currents. Chemical sensors provide equivalents of [[taste]] and [[Olfaction|smell]], often by means of setae.<ref name="RuppertFoxBarnes2004P532To537">{{harvnb|Ruppert|Fox|Barnes|2004|pp=532–537}}</ref>

Living chelicerates have both [[compound eye]]s (only in [[horseshoe crab]]s, as the compound eye in the other clades has been reduced to a cluster of no more than five pairs of [[ocelli]]), mounted on the sides of the head, plus pigment-cup ocelli ("little eyes"), mounted in the middle. These median ocelli-type eyes in chelicerates are assumed to be [[Homology (biology)|homologous]] with the crustacean nauplius eyes and the insect ocelli.<ref>{{cite journal | pmc=4450993 | pmid=26034575 | doi=10.1186/s13227-015-0010-x | volume=6 | title=Differential expression of retinal determination genes in the principal and secondary eyes of Cupiennius salei Keyserling (1877) | journal=Evodevo | page=16 |vauthors=Samadi L, Schmid A, Eriksson BJ| year=2015 | doi-access=free }}</ref> The eyes of horseshoe crabs can detect movement but not form images.<ref name="RuppertFoxBarnes2004Xiphosura" /> At the other extreme, [[jumping spider]]s have a very wide field of vision,<ref name="RuppertFoxBarnes2004Spiders" /> and their main eyes are ten times as acute as those of [[dragonfly|dragonflies]],<ref name="HarlandJackson2000EightLeggedCats">{{cite journal |author1=Harland, D.P. |author2=Jackson, R.R. |year=2000 |title="Eight-legged cats" and how they see - a review of recent research on jumping spiders (Araneae: Salticidae) |journal=Cimbebasia |volume=16 |pages=231–240 |url=http://www.cogs.susx.ac.uk/ccnr/Papers/Downloads/Harland_Cimb2000.pdf |access-date=2008-10-11 |df=dmy-all |archive-url=https://web.archive.org/web/20060928164131/http://www.cogs.susx.ac.uk/ccnr/Papers/Downloads/Harland_Cimb2000.pdf |archive-date=2006-09-28 }}</ref> able to see in both colors and UV-light.<ref>{{cite web |url=http://www.nbcnews.com/id/49454132/ns/technology_and_science-science/t/their-eight-eyes-jumping-spiders-are-true-visionaries/ |archive-url=https://archive.today/20130629234221/http://www.nbcnews.com/id/49454132/ns/technology_and_science-science/t/their-eight-eyes-jumping-spiders-are-true-visionaries/ |url-status=dead |archive-date=June 29, 2013 |title=With their eight eyes, jumping spiders are true visionaries|website=[[NBC News]] |date=2012-10-17}}</ref>