Editing Phasmatodea (section)

==Description==
[[File:Giant Stick Insect (Phobaeticus serratipes) on Sylvain (8727651923).jpg|thumb|left|''[[Phobaeticus serratipes]]'']]
[[File:Phobaeticus chani Bragg, 2008; Holotype Female dorsal view.jpg|thumb|left|upright=1.5<!--width for very low image-->|Female ''[[Phobaeticus chani]]'', the world's second-longest insect. This species grows to a total length of {{cvt|56.7|cm}} (front legs fully extended) and body length of {{cvt|35.7|cm}}.<ref>{{cite web|url= http://www.nhm.ac.uk/about-us/news/2008/october/worlds-longest-insect-revealed.html|title= World's longest insect revealed|access-date= 2008-10-16|publisher= [[Natural History Museum, London|Natural History Museum]]|date= 2008-10-16|url-status= dead|archive-url= https://web.archive.org/web/20081019104055/http://www.nhm.ac.uk/about-us/news/2008/october/worlds-longest-insect-revealed.html|archive-date= 2008-10-19}}</ref>]]

Phasmids vary greatly in size, with females typically growing larger than males of the same species.<ref>{{cite book | last1=Bradler | first1=S. | last2=Buckley | first2=T.R. | year=2018 | title=Insect Biodiversity: Science and Society | chapter=Biodiversity of Phasmatodea | pages=281–313 | volume=II | editor=Foottit, R.G. | editor2=Adler, P.H. | publisher=John Wiley & Sons Ltd | doi=10.1002/9781118945582.ch11 | isbn=978-1-118-94557-5 }}</ref> Males of the smallest species, such as ''[[Timema cristinae]]'', reach about {{convert|2|cm|in|1}} long,<ref>{{Cite journal|last=Vickery|first=V.R.|date=1993|title=Revision of ''Timema'' Scudder (Phasmatoptera: Timematodea) including three new species|journal=The Canadian Entomologist|volume=125|issue=4|pages=657–692|doi=10.4039/ent125657-4|s2cid=86710665 |issn=0008-347X}}</ref> while females of the longest, an [[undescribed species]] informally known as ''[[Phryganistria chinensis|Phryganistria "chinensis"]]'', can be up to {{convert|64|cm|in}} in total length, including outstretched legs. This makes it the [[List of largest insects#Stick insects (Phasmatodea)|world's longest insect]].<ref>{{Cite web|url=https://www.iflscience.com/plants-and-animals/worlds-new-longest-insect-is-the-length-of-your-arm/|title=World's New Longest Insect Is The Length Of Your Arm|last=Hale|first=Tom|date=14 August 2017|website=IFLScience|language=en|access-date=2020-03-27}}</ref> The heaviest species of phasmid is likely to be ''[[Heteropteryx dilatata]]'', the females of which may weigh as much as {{convert|65|g|oz|1|abbr=on}}.<ref>{{cite web|title=Phasmids: An Introduction to the Stick Insects and Leaf Insects|url=http://phasmid-study-group.org/content/Phasmids-Introduction-Stick-Insects-and-Leaf-Insects|access-date=22 March 2011}}</ref>

Some phasmids have cylindrical stick-like shapes, while others have flattened, leaflike shapes. Many species are wingless, or have reduced wings.<ref name=IIBD>{{cite book |author1=Hoell, H.V. |author2=Doyen, J.T. |author3=Purcell, A.H. |year=1998 |title=Introduction to Insect Biology and Diversity |edition=2nd |publisher= Oxford University Press |pages= 398–399|isbn= 978-0-19-510033-4}}</ref> The [[Thorax (insect anatomy)|thorax]] is long in the winged species, since it houses the flight muscles, and is typically much shorter in the wingless forms. Where present, the first pair of wings is narrow and [[Keratin|cornified]] (hardened), while the hind wings are broad, with straight veins along their length and multiple cross-veins. Their wing [[Insect wing#Venation|venation]] is unique among insects.<ref>[https://hal.archives-ouvertes.fr/hal-02349207/document To be or not to be: postcubital vein in insects revealed by microtomography]</ref> The body is often further modified to resemble vegetation, with ridges resembling leaf veins, bark-like [[tubercles]], and other forms of [[camouflage]]. A few species, such as ''[[Carausius morosus]]'', are even able to change their [[Biological pigments|pigmentation]] to match their surroundings. The [[Insect mouthparts|mouthparts]] project out from the head. Chewing [[Mandible (insect mouthpart)|mandibles]] are uniform across species. The legs are typically long and slender, and some species are capable of limb [[autotomy]] (appendage shedding).<ref name=IIBD/> Phasmids have long, slender [[Antenna (biology)|antennae]], as long as or longer than the rest of the body in some species.

[[File:Australian Leaf Insect, portrait.jpg|thumb|left|Head of a female ''[[Extatosoma tiaratum]]'']]
All phasmids possess [[compound eye]]s, but [[Simple eye in invertebrates#Dorsal ocelli|ocelli]] (light-sensitive organs) are only known from the five groups Lanceocercata, Necrosciinae, Pseudophasmatidae, Palophidae and Phylliidae. Of these only the first three groups have females with ocelli, which like the wings seems to have re-evolved from ancestors that had lost them.<ref>[https://bmcecolevol.biomedcentral.com/articles/10.1186/s12862-022-02018-5 A second view on the evolution of flight in stick and leaf insects (Phasmatodea)]</ref> Phasmids have an impressive visual system that allows them to perceive significant detail even in dim conditions, which suits their typically [[nocturnal]] lifestyle. They are born equipped with tiny compound eyes with a limited number of facets. As phasmids grow through successive [[moulting|molts]], the number of facets in each eye is increased along with the number of [[photoreceptor cell]]s. The sensitivity of the adult eye is at least tenfold that of the nymph in its first [[instar]] (developmental stage). As the eye grows more complex, the mechanisms to adapt to dark/light changes are also enhanced: eyes in dark conditions evidence fewer screening pigments, which would block light, than during the daytime, and changes in the width of the retinal layer to adapt to changes in available light are significantly more pronounced in adults. The larger size of the adult insects' eyes makes them more prone to radiation damage. This explains why fully grown individuals are mostly nocturnal. Lessened sensitivity to light in the newly emerged insects helps them to escape from the [[leaf litter]] wherein they are hatched and move upward into the more brightly illuminated foliage. Young stick insects are [[Diurnality|diurnal]] (daytime) feeders and move around freely, expanding their [[foraging]] range.<ref>{{cite journal |last=Meyer-Rochow |first=V. Benno |author2=Essi Keskinen |title=Post-embryonic photoreceptor development and dark/light adaptation in the stick insect Carausius morosus (Phasmida, Phasmatidae) |journal=Applied Entomology and Zoology |year=2003 |volume=38 |issue=3 |pages=281–291 |doi=10.1303/aez.2003.281|doi-access=free|bibcode=2003AppEZ..38..281M }}</ref>

Stick insects have two types of pads on their legs: sticky "toe pads" and non-stick "heel pads" a little further up their legs. The heel pads are covered in microscopic hairs which create strong friction at low pressure, enabling them to grip without having to be peeled energetically from the surface at each step. The sticky toe pads are used to provide additional grip when climbing but are not used on a level surface.<ref>{{cite web |title=How stick insects honed friction to grip without sticking |url=http://phys.org/news/2014-02-insects-honed-friction.html |publisher=Phys.org |access-date=3 October 2015 |date=19 February 2014}}</ref>