Editing Aphid (section)

==Anatomy==
[[File:Schizaphis graminum usda (cropped).jpg|thumb|Front view of [[wheat]] aphid, ''[[Schizaphis graminum]]'', showing the piercing-sucking mouthparts]]

Most aphids have soft bodies, which may be green, black, brown, pink, or almost colorless. Aphids have [[Antenna (zoology)|antennae]] with two short, broad basal segments and up to four slender terminal segments. They have a pair of [[compound eye]]s, with an ocular [[tubercle]] behind and above each eye, made up of three lenses called triommatidia.<ref name="Dixon"/> They feed on sap and plant fluids using [[piercing-sucking mouthpart]]s called [[stylet (anatomy)|stylet]]s, enclosed in a sheath called a [[Rostrum (anatomy)|rostrum]], which is formed from modifications of the [[Mandible (insect mouthpart)|mandible]] and [[Maxilla (arthropod mouthpart)|maxilla]] of the insect mouthparts.<ref name="Stroyan">{{cite encyclopedia |author=Stroyan, Henry G. |title=Aphid |encyclopedia=[[McGraw-Hill Encyclopedia of Science and Technology]] |edition=8th |year=1997 |isbn=978-0-07-911504-1}}</ref>

They have long, thin legs with two-jointed, two-clawed [[Arthropod leg|tarsi]]. The majority of aphids are wingless, but winged forms are produced at certain times of year in many species. Most aphids have a pair of [[cornicle]]s (siphunculi), abdominal tubes on the dorsal surface of their fifth abdominal segment, through which they exude droplets of a quick-hardening defensive fluid<ref name=Stroyan/> containing [[triacylglycerol]]s, called cornicle wax. Other defensive compounds can also be produced by some species.<ref name="McGavin"/> Aphids have a tail-like protrusion called a cauda above their rectal apertures.<ref name="Dixon">{{cite book |author=Dixon, A. F. G. |title=Aphid Ecology |publisher=[[Chapman and Hall]] |year=1998 |isbn=978-0-412-74180-7 |url=https://books.google.com/books?id=3GHhGJC9z9EC&pg=PA4 |edition=2nd |access-date=2016-05-24 |archive-date=2013-02-18 |archive-url=https://web.archive.org/web/20130218200641/http://books.google.com/books?id=3GHhGJC9z9EC&pg=PA4 |url-status=live }}</ref><ref>{{Cite thesis |url=http://krex.k-state.edu/dspace/bitstream/2097/154/1/NavdeepMutti2006.pdf |title=Molecular Studies of the Salivary Glands of the Pea Aphid, ''Acyrthosiphon pisum'' (Harris) |author=Mutti, Navdeep S. |degree=[[Doctor of Philosophy|Ph.D.]] |publisher=[[Kansas State University]] |year=2006 |access-date=2008-07-12 |archive-date=2012-02-27 |archive-url=https://web.archive.org/web/20120227160826/http://krex.k-state.edu/dspace/bitstream/2097/154/1/NavdeepMutti2006.pdf |url-status=live }}</ref> They have lost their [[Malpighian tubule system|Malpighian tubules]].<ref>{{Cite journal|title=The molecular correlates of organ loss: the case of insect Malpighian tubules - PMC|year=2015 |pmc=4455741 |last1=Jing |first1=X. |last2=White |first2=T. A. |last3=Yang |first3=X. |last4=Douglas |first4=A. E. |journal=Biology Letters |volume=11 |issue=5 |doi=10.1098/rsbl.2015.0154 |pmid=25972400 }}</ref>

When host plant quality becomes poor or conditions become crowded, some aphid species produce winged offspring ([[alate]]s) that can disperse to other food sources. The mouthparts or eyes can be small or missing in some species and forms.<ref name="McGavin"/>