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Proleg

Anatomical structure

Wikipedia contributorsAdapted for Fathomly · View authors
2 min read
Source updated August 24, 2026
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A proleg is a small, fleshy, stub structure found on the ventral surface of the abdomen of most larval forms of insects of the order Lepidoptera, though they can also be found on larvae of insects such as sawflies.

01Variations

In all the orders in which they appear, mainly Hymenoptera and Lepidoptera, prolegs of any form evolved independently of each other by convergent evolution. They appear to have evolved from ancient inactive genes that have since been activated again.

Prolegs of lepidopteran larvae have a small circle of gripping hooks, called "crochets". The arrangement of the crochets can be helpful in identification to family level. Although the point has been debated, prolegs are not widely regarded as true legs, derived from the primitive 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 hydraulically powered.

Hymenoptera: Craesus septentrionalis caterpillars with seven pairs of prolegs
Hymenoptera: Craesus septentrionalis caterpillars with seven pairs of prolegs

02Number of prolegs for various insect larvae

Number of prolegs on insect larvae at abdominal segments A1-A9/10=S4-12/13 (T1-3: thorax segments with 6 legs)
Larvae ofGroup/
Family		OrderA1=S4A2=S5A3=S6A4=S7A5=S8A6=S9A7=S10A8=S11A9/10=S12/13
(anal proleg
pygopodium)		legs
total
incl T1-3
Butterflies/MothsmanyLepidoptera--2222--216
Archaic mothsMicropterygidaeLepidoptera22222222224
Owlet moths and alliesNoctuoidea (some)Lepidoptera---222--214
Owlet moths and alliesNoctuoidea (some)Lepidoptera----22--212
Geometer mothsGeometridaeLepidoptera-----2--210
Geometer mothsGeometridae (very few species)Lepidoptera----22--212
SawfliesSymphyta (many)Hymenoptera-2222222222
SawfliesSymphyta (some)Hymenoptera-222222-220
SawfliesSymphyta (some)Hymenoptera-22222--218
some? PamphiliidaePamphiliinaeHymenoptera--------28
MecopteraallMecoptera22222222224
CaddisfliesallTrichoptera--------28

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

J: medial prolegsK: anal proleg(F, G, and H: true legs)
J: medial prolegsK: anal proleg(F, G, and H: true legs)
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Sources and credits

This article is adapted from the Wikipedia article “Proleg”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.

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