Editing Lepidoptera (section)

== External morphology ==
{{main|External morphology of Lepidoptera}}
{{further|Glossary of entomology terms|Comparison of butterflies and moths}}
[[File:Butterfly parts.svg|thumb|upright=1.4|Parts of an adult butterfly]]
[[File:Caterpillar morphology diagram.svg|thumb|upright=1.4|A – head, B – thorax, C – abdomen,
1 – prothoracic shield,
2 – spiracle,
3 – true legs,
4 – midabdominal prolegs,
5 – anal proleg,
6 – anal plate,
7 – tentacle,
a – eye,
b – stemmata (ocelli),
c – antenna,
d – mandible,
e – labrum, 
f – frontal triangle.]]
Lepidoptera are morphologically distinguished from other orders principally by the presence of [[scale (Lepidoptera)|scale]]s on the external parts of the body and appendages, especially the [[Insect wing|wings]]. Butterflies and moths vary in size from [[microlepidoptera]] only a few millimeters long, to conspicuous animals with a wingspan greater than {{Convert|25|cm|in}}, such as the [[Queen Alexandra's birdwing]] and [[Atlas moth]].<ref name="Gillot">{{cite book |title=Entomology |last=Gillot |first=C. |edition=2 |year=1995 |isbn=978-0-306-44967-3 |pages=246–266 |chapter-url=https://books.google.com/books?id=DrTKxvZq_IcC |access-date=14 November 2010 |chapter=Butterflies and moths |publisher=Springer |archive-date=10 March 2017 |archive-url=https://web.archive.org/web/20170310082058/https://books.google.com/books?id=DrTKxvZq_IcC |url-status=live }}</ref>{{Rp|246}}
Lepidopterans undergo a four-stage [[Biological life cycle|life cycle]]: [[egg]]; [[larva]] or [[caterpillar]]; [[pupa]] or [[chrysalis]]; and [[imago|imago (plural: imagines)]] / adult and show many variations of the basic body structure, which give these animals advantages for diverse lifestyles and environments.

=== Head ===
[[File:Caterpillar face close up.jpg|thumb|left|Face of a caterpillar with the mouthparts showing]]
The head is where many sensing organs and the mouth parts are found. Like the adult, the larva also has a toughened, or [[sclerite|sclerotized]] head capsule.<ref name="scoble_heads">Scoble (1995). Section ''The Adult Head – Feeding and Sensation'', (pp. 4–22).</ref> Here, two [[compound eye]]s, and ''chaetosema'', raised spots or clusters of sensory bristles unique to Lepidoptera, occur, though many taxa have lost one or both of these spots. The antennae have a wide variation in form among species and even between different sexes. The antennae of butterflies are usually filiform and shaped like clubs, those of the skippers are hooked, while those of moths have flagellar segments variously enlarged or branched. Some moths have enlarged antennae or ones that are tapered and hooked at the ends.<ref name="Resh and Carde">{{cite book |last=Resh |first=Vincent H. |author2=Ring T. Carde  |title=Encyclopedia of Insects |publisher=Academic Press |location=U. S. A. |date=1 July 2009 |edition=2 |isbn=978-0-12-374144-8}}</ref>{{Rp|559–560}}

The [[Galea (insects)|maxillary galeae]] are modified and form an elongated [[proboscis]]. The proboscis consists of one to five segments, usually kept coiled up under the head by small muscles when it is not being used to suck up nectar from flowers or other liquids. Some [[basal (phylogenetics)|basal]] moths still have [[mandible (insect mouthpart)|mandible]]s, or separate moving jaws, like their ancestors, and these form the family [[Micropterigidae]].<ref name="scoble_heads"/><ref name="Resh and Carde"/>{{Rp|560}}<ref name="Firefly">{{Cite book|last=Christopher|first=O'Toole|title=Firefly Encyclopedia of Insects and Spiders|edition=1|isbn=978-1-55297-612-8|url=https://archive.org/details/fireflyencyclope0000unse_k0d2|year=2002|publisher=Firefly Books |url-access=registration}}</ref>

The larvae, called [[caterpillar]]s, have a toughened head capsule. Caterpillars lack the proboscis and have separate chewing [[Insect mouthparts|mouthparts]].<ref name="scoble_heads"/> These mouthparts, called [[mandible (insect mouthpart)|mandible]]s, are used to chew up the plant matter that the larvae eat. The lower jaw, or labium, is weak, but may carry a [[spinneret]], an organ used to create silk. The head is made of large lateral lobes, each having an ellipse of up to six simple eyes.<ref name="Resh and Carde"/>{{Rp|562–563}}

=== Thorax ===
The thorax is made of three fused segments, the [[prothorax]], [[mesothorax]], and [[metathorax]], each with a pair of legs. The first segment contains the first pair of legs. In some males of the butterfly family [[Nymphalidae]], the forelegs are greatly reduced and are not used for walking or perching.<ref name="Resh and Carde"/>{{Rp|586}} The three pairs of legs are covered with scales. Lepidoptera also have olfactory organs on their feet, which aid the butterfly in "tasting" or "smelling" out its food.<ref name="Heppner">{{cite book |last1=Heppner |first1=J. B. |editor1-first=John L. |editor1-last=Capinera |title=Encyclopedia of Entomology |url=https://books.google.com/books?id=i9ITMiiohVQC |edition=2 |series=Gale virtual reference library |volume=4 |year=2008 |publisher=Springer Reference |isbn=978-1-4020-6242-1 |page=4345 |chapter=Butterflies and moths |chapter-url=https://books.google.com/books?id=i9ITMiiohVQC&pg=PA626 |access-date=22 September 2016 |archive-url=https://web.archive.org/web/20160624051424/https://books.google.com/books?id=i9ITMiiohVQC |archive-date=24 June 2016 |url-status=live }}</ref> In the larval form there are 3 pairs of true legs, with up to 11 pairs of abdominal legs (usually eight) and hooklets, called apical crochets.<ref name="cgillott"/>

The two pairs of wings are found on the middle and third segments, or [[mesothorax]] and [[metathorax]], respectively. In the more recent genera, the wings of the second segment are much more pronounced, although some more primitive forms have similarly sized wings of both segments. The wings are covered in scales arranged like shingles, which form an extraordinary variety of colors and patterns. The mesothorax has more powerful muscles to propel the moth or butterfly through the air, with the wing of this segment (forewing) having a stronger vein structure.<ref name="Resh and Carde"/>{{Rp|560}} The largest superfamily, the [[Noctuoidea]], has their wings modified to act as [[Tympanal organ|tympanal or hearing organ]]s.<ref name="Scoble">{{cite book |last1=Scoble|first1=MJ. |title=The Lepidoptera: Form, function, and diversity. |url=https://archive.org/details/lepidopteraformf0000scob|url-access=registration|year=1992 |publisher=Oxford Univ. Press|isbn=978-1-4020-6242-1}}</ref><!-- could include the case of fringed wings -->

The caterpillar has an elongated, soft body that may have hair-like or other projections, three pairs of true legs, with none to 11 pairs of abdominal legs (usually eight) and hooklets, called apical crochets.<ref name="cgillott"/> The thorax usually has a pair of legs on each segment. The thorax is also lined with many spiracles on both the mesothorax and metathorax, except for a few aquatic species, which instead have a form of [[gill]]s.<ref name="Resh and Carde"/>{{Rp|563}}

=== Abdomen ===
{{See also|Lepidoptera genitalia}}
[[File:Chenille de Grand porte queue (macaon) Fausses pattes.jpg|thumb|Caterpillar prolegs on ''[[Papilio machaon]]'']]

The abdomen, which is less sclerotized than the thorax, consists of 10 segments with membranes in between, allowing for articulated movement. The sternum, on the first segment, is small in some families and is completely absent in others. The last two or three segments form the external parts of the species' sex organs. The [[Lepidoptera genitalia|genitalia]] of Lepidoptera are highly varied and are often the only means of differentiating between species. Male genitals include a [[valva]], which is usually large, as it is used to grasp the female during mating. Female genitalia include three distinct sections.

The females of basal moths have only one sex organ, which is used for [[copulation (zoology)|copulation]] and as an [[ovipositor]], or egg-laying organ. About 98% of moth species have a separate organ for mating, and an external duct that carries the sperm from the male.<ref name="Resh and Carde"/>{{Rp|561}}

The abdomen of the caterpillar has four pairs of prolegs, normally located on the third to sixth segments of the abdomen, and a separate pair of prolegs by the anus, which have a pair of tiny hooks called crotchets. These aid in gripping and walking, especially in species that lack many prolegs (e. g. larvae of [[Geometridae]]). In some basal moths, these prolegs may be on every segment of the body, while prolegs may be completely absent in other groups, which are more adapted to boring and living in sand (e. g., [[Prodoxidae]] and [[Nepticulidae]], respectively).<ref name="Resh and Carde"/>{{Rp|563}}

=== Scales ===
[[File:Mottenflügel in Mikroskop.jpg|thumb|right|Wing scales form the color and pattern on wings. The scales shown here are lamellar. The pedicel can be seen attached to a few loose scales.]]

The wings, head, and parts of the thorax and abdomen of Lepidoptera are covered with minute scales, a feature from which the order derives its name. Most scales are [[lamella (anatomy)|lamella]]r, or blade-like, and attached with a pedicel, while other forms may be hair-like or specialized as secondary sexual characteristics.<ref name="Scoble scale">Scoble (1995). Section ''Scales'', (pp. 63–66).</ref>

The lumen or surface of the lamella has a complex structure. It gives color either by colored [[pigment]]s it contains, or through [[structural coloration]] with mechanisms that include [[photonic crystal]]s and [[diffraction grating]]s.<ref name="Vukusic (2006)">{{cite journal |last1=Vukusic |first1=P. |year=2006 |title=Structural color in Lepidoptera |journal=Current Biology |pmid=16920604 |volume=16 |issue=16 |pages=R621–3 |doi=10.1016/j.cub.2006.07.040 |s2cid=52828850 |doi-access=free |bibcode=2006CBio...16.R621V }}</ref>

Scales function in insulation, thermoregulation, producing [[pheromones]] ([[androconia|in males only]]),<ref>{{cite journal |last1=Hall |first1=Jason P. W. |last2=Harvey |first2=Donald J. |year=2002 |title=A survey of androconial organs in the Riodinidae (Lepidoptera) |journal=[[Zoological Journal of the Linnean Society]] |volume=136 |issue=2 |pages=171–197 |doi=10.1046/j.1096-3642.2002.00003.x |doi-access=free }}</ref> and aiding gliding flight, but the most important is the large diversity of vivid or indistinct [[patterns in nature|patterns]] they provide, which help the organism protect itself by [[camouflage]] or [[mimicry]], and which act as signals to other animals including rivals and [[sexual selection|potential mates]].<ref name="Scoble scale"/>
{{Multiple image
| direction=horizontal
| align = left
| width = 180
| header = Electron microscopy images of scales
| image1 = SEM_image_of_a_Peacock_wing%2C_slant_view_1.JPG
| caption1 = A patch of wing (×50)
| image2 = SEM_image_of_a_Peacock_wing,_slant_view_2.JPG
| caption2 = Scales close up (×200)
| image3 = SEM_image_of_a_Peacock_wing,_slant_view_3.JPG
| caption3 = A single scale (×1000)
| image4 = SEM_image_of_a_Peacock_wing,_slant_view_4.JPG
| caption4 = Microstructure of a scale (×5000)
}}{{Clear}}