View source for Proleg

{{Short description|Anatomical structure}}
[[File:Caterpillar-description.jpg|thumb|upright|left|J: medial prolegs<br />K: anal proleg<br />(F, G, and H: true legs)]]
[[File:Chenille de Grand porte queue (macaon) Fausses pattes.jpg|thumb|upright=1|right|Lepidoptera: ''[[Papilio machaon]] '' caterpillar with four pairs of medial prolegs and a pair of anal prolegs]]
[[File:Craesus septentrionalis.jpg|thumb|upright=1|right|Hymenoptera: ''[[Craesus septentrionalis]]'' caterpillars with seven pairs of prolegs]]
A '''proleg''' is a small, fleshy, stub structure found on the ventral surface of the [[abdomen]] of most [[larva]]l forms of [[insect]]s of the [[Order (biology)|order]] [[Lepidoptera]], though they can also be found on larvae of insects such as [[symphyta|sawflies]]. In all the orders in which they appear, mainly [[Hymenoptera]] and Lepidoptera, prolegs of any form evolved independently of each other by [[convergent evolution]].<ref>{{Cite journal | last1 = Suzuki | first1 = Y. | last2 = Palopoli | first2 = M. | doi = 10.1007/s00427-001-0182-3 | title = Evolution of insect abdominal appendages: Are prolegs homologous or convergent traits? | journal = Development Genes and Evolution | volume = 211 | issue = 10 | pages = 486–492 | year = 2001 | pmid =  11702198| s2cid = 1163446 }}</ref> They appear to have evolved from ancient inactive genes that have since been activated again.<ref>[https://www.science.org/doi/10.1126/sciadv.add9389 Lepidopteran prolegs are novel traits, not leg homologs]</ref>

Prolegs of lepidopteran larvae have a small circle of gripping hooks, called "'''crochets'''".  The arrangement of the crochets can be helpful in identification to [[Rank (zoology)|family]] level.<ref name= "isbn0-412-61390-5">{{cite book |author1=Richards, O. W. |author2=Davies, R.G. |title=Imms' General Textbook of Entomology: Volume 1: Structure, Physiology and Development Volume 2: Classification and Biology |publisher=Springer |location=Berlin |year=1977 |isbn=0-412-61390-5 }}</ref> Although the point has been debated, prolegs are not widely regarded as true [[arthropod leg|legs]], derived from the primitive [[Arthropod leg#Biramous and uniramous|uniramous]] limbs. Certainly in their morphology they are not jointed, and so lack the five segments (coxa, trochanter, femur, tibia, tarsus) of thoracic insect legs. Prolegs do have limited musculature, but much of their movement is [[Hydraulics|hydraulically]] powered.

==Number of prolegs for various insect larvae==

{| class="wikitable sortable zebra"
|+ style="padding-bottom:1em"| Number of prolegs on insect larvae at abdominal segments A1–A9/10=S4-12/13 (T1–3: thorax segments with 6 legs)<ref name="Keler">Stefan von Kéler: Entomologisches Wörterbuch. Akademie-Verlag Berlin 1963. p. 80.</ref>
|- class="hintergrundfarbe6"
! Larvae of !! Group/<br />Family !! Order !! A1=S4 !! A2=S5 !! A3=S6 !! A4=S7 !! A5=S8 !! A6=S9 !! A7=S10 !! A8=S11 !! A9/10=S12/13<br />(anal proleg<br/>pygopodium) !! legs<br />total<br />incl T1–3
|-
|[[Lepidoptera|Butterflies/Moths]]||many||[[Lepidoptera]]||-||-||2||2||2||2||-||-||2||16
|-
|[[Micropterigidae|Archaic moths]]||Micropterygidae||Lepidoptera||2||2||2||2||2||2||2||2||2||24
|-
|[[Noctuidae|Owlet moths]]||[[Noctuidae]] (some)||Lepidoptera||-||-||-||2||2||2||-||-||2||14
|-
|Owlet moths||Noctuidae (some)||Lepidoptera||-||-||-||-||2||2||-||-||2||12
|-
|[[Geometridae|Geometer moths]]||[[Geometridae]]||Lepidoptera||-||-||-||-||-||2||-||-||2||10
|-
|[[Geometridae|Geometer moths]]||[[Geometridae]]  (very few species)||Lepidoptera||-||-||-||-||2||2||-||-||2||12
|-
|[[Sawfly|Sawflies]]||[[Symphyta]] (many)||[[Hymenoptera]]||-||2||2||2||2||2||2||2||2||22
|-
|Sawflies||Symphyta (some)||Hymenoptera||-||2||2||2||2||2||2||-||2||20
|-
|Sawflies||Symphyta (some)||Hymenoptera||-||2||2||2||2||2||-||-||2||18
|-
|some? [[Pamphiliidae]]||Pamphiliinae||Hymenoptera||-||-||-||-||-||-||-||-||2||8
|-
|[[Mecoptera]]||all||Mecoptera||2||2||2||2||2||2||2||2||2||24
|-
|[[Caddisfly|Caddisflies]]||all||[[Trichoptera]]||-||-||-||-||-||-||-||-||2||8
|-
|}

Additional (stubby) prolegs on segment 8 have been reported on the Geometridae species [[Campaea perlata]] and [[Alsophila pometaria]].

== See also ==
* [[Terrestrial locomotion in animals]]

==References==
{{reflist}}
* Peterson, A. 1948. ''Larvae Of Insects. Part I: Lepidoptera & Hymenoptera; Part II: Coleoptera, Diptera, Neuroptera, Siphonaptera, Mecoptera, Trichoptera.'' Columbus, OH.
* Richards, O.W. & R.G. Davies. 1977. ''Imm's General Textbook of Entomology'', 10th ed. (2 Volumes). Chapman & Hall, London.
* Snodgrass, R.E. 1935 (1993 reprint). ''Principles of Insect Morphology''. Cornell University Press, Ithaca, NY.

==External links==
{{wiktionary|proleg}}
* [https://web.archive.org/web/20060208090144/http://www-staff.it.uts.edu.au/~don/larvae/faqs/legs.html How Many Legs Do Caterpillars Have?]

[[Category:Insect anatomy]]
[[Category:Larvae]]


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