Insect legs and it's modifications

Insect legs and it's modifications

1. Insectlegsandit'smodifications
IMRANULHASSANSOLANGI
Session2019-20
DepartmentofZoology
ShahAbdulLatifUniversity(SALU)Khairpur

2. CONTENT
IntroductionofInsectsoflegs
Structureoftypicalinsectlegs
TYPESOFINSECT’SLEGS
Saltatorial—jumping
Raptorial—seizing
Fossorial—digging
Natatorial—swimming
Cursorial—running
Scansoria---Climbing
Ambulatorial---walking

3. InsectLegs:-
Insecthavethreepairsoflegs,onepaironeachofthethreesegmentsofthethoraxandare
generallycalledthefore-,mid-,andhindlegs.Anyofthepairsoflegsmaybeheavilymodifiedand
areimportantforlocomotion,preycapture,mating,etc.Thankfully,justlikemouthparts,allinsect
legscontainthesamebasicparts.Fromproximal(towardoragainstthebody)todistal(awayfrom
thebody)thepartsofaninsectlegare:coxa,trochanter,femur,tibia,andtarsus.Thetarsus
almostalwayshasoneortwoclawsatthetypeusedtograspthesubstrate.ThefigureInsectLegs,
right,showslegsmodifiedfornumerouspurposes:A,running;B,jumping;C,digging;D,grasping;E,
catching;F,walkinganddigging;G,reducedlegusedforwalkinganddigging;H,malelegmodified
forgraspingfemalesduringmating.
AbdominalProlegs
Someinsectlarvae,suchascaterpillars,havepairsofshortfleshylegsononeormoreabdominal
segments.Theselegsmayhavetinyhooksorbarbs(calledcrochets)thatservetogripthe
substrate.Abdominalprolegsneveroccurinaninsect’sadultstage.Theyareauniquelarval
adaptationderivedfromacompletelydifferentembryologicaloriginthanthethoraciclegs.

4. Structureoftypicalinsectlegs
Consistof5segmentsnamelyCoxa,trochanter,femur,tibiaandtarsus.Tarsusconsistof1-5small
segmentscalledtarsomeres.LasttarsomerebearsapairofclawsApadbetweentheclawsiscalled
AroliumPadsatthebaseofclawsarecalledpulvilli.
Whilethelegsarenormallyadaptedforwalkingmanyinsectshavethemmodifiedforvarietyof
functions.VariousmodificationsareSaltatoriallegs–Hindlegsadaptedforleapingofjumping.The
femurisgreatlyenlargedgivingarticulationforlargemusclesoftibiawhichareusedinjumping
occurinGrasshopper,Cricket.
Thetermpretarsusreferstotheterminalsegmentofthetarsusandanyotherstructuresattachedto
it,including:
 ungues—apairofclaws
 arolium—alobeoradhesivepadbetweentheclaws
 empodium—alargebristle(orlobe)betweentheclaws
 pulvilli—apairofadhesivepads

5. TYPESOFINSECT’SLEGS
Saltatorial—jumping
Raptorial—seizing
Fossorial—digging
Natatorial—swimming
Cursorial—running
Scansoria---Climbing
Ambulatorial---walking
Saltatorial:(Salatorial=Leaping:JumpingLeg)
Saltatoriallegsarejumpinglegs.You’veallseenthesekindsoflegs
before!Grasshoppersaretheposterinsectsforsaltatoriallegs,butotherjumping
insectslikefleashavethemaswell.Saltatoriallegsworkwellforjumpingbecause
theyareenlargedlegsfilledwithbulky,strongmuscles.Allthosemusclesallow
insectswiththistypeoflegtojump,propellingthemselvesforwardverylong
distancesveryquickly.Saltatoriallegsareusuallyhindlegs.
e.g.hindlegofgrasshopper.
Raptorial:(Raptorial=predatory;Graspingleg)
Youarelikelyfamiliarwiththissortoflegtoo.Raptoriallegsarehuntinglegs,the
kindsoflegsyouseeonpredatoryinsectssuchasmantidsandgiantwaterbugs.Like
thesaltatoriallegs,theseareenlargedlegsfullofstrong,powerfulmuscles.However,
theselegsareusuallyatthefrontoftheinsectandareusedtograbandholdprey
whiletheyeat.Manyinsectswithraptoriallegsholdthemoutinfrontoftheirbodies,
positionedsothattheycanstrikeatpreyatanytime.
e.g.Forelegsofpreyingmantis.

6. Fossorial:(Fossorial=Digging;Burrowingleg)
Insectswithfossoriallegsliveundergroundandusetheirhighlymodifiedlegs,
usuallytheforelegs,todigburrows.Themolecricket,theforlegsofwhichare
picturedatleft,areaprimeexample.Fossoriallegstendtobeverybroad,veryflat,
andverydense.Theyoftenhavebig,strongclaws.Fossoriallegsworksomewhat
likeshovelstoripsoilsapartquicklyandeasilyandallowtheinsecttoburyitselfin
thegroundsurprisinglyquickly.Thistypeoflegismuchlesscommonthantheothers,
butit’sathrilltofindaninsectthathasthem!They’rereallyimpressive.
e.g.Forelegsofmolecricket.
Natatorial:(Natatorial=pertainingtoswimming;Swimmingleg)
Natatorialisanotherwordforswimming,soinsectswithnatatoriallegsareaquatic
insectsthatrequiremodifiedlegstomoveeasilythroughwater.Natatoriallegsare
oftenflattened,broad,andfringedwithdensehairs,asintheimageofthepredaceous
divingbeetlehindlegpicturedatright.Theseadaptationshavethesamesortofeffect
asahumanwearingflippersastheyswim–theyincreasethesurfaceareaofthelegs
astheykick,allowingtheinsecttomovemoreeasilythroughwater.Manyaquatic
insectsexhibitnatatoriallegs,especiallyinthehindandmiddlepairsoflegs,butnot
allofthemdo.Theyareespeciallycommoninaquaticbeetlesandbugs.
e.g.hinglegsofwaterbugandwaterbeetle.

7. Cursorial:(Cursorial=adaptedforrunning:Runningleg)
Thesearethetypesoflegsmostpeoplelikelythinkofifthey’veeverponderedinsect
legsbefore.Cursorialisafancywordforrunning,sothesearethekindsoflegsyou
seeonswiftlymovinginsectssuchasroachesandtigerbeetles.Cursoriallegstendto
belongandnarrowandaredesignedsothattheinsectcanmoveveryquickly.Things
withthistypeoflegareoftenhardtocatch–orhardtosteponifyou’redealingwith
roaches.
e.g.Allthethreepairsoflegsofcockroach.Legsaresuitedforrunning.Femurisnot
swollen.
Ambulatorial(Ambulate-towalk;Walkingleg)
e.g.Forelegandmiddlelegofgrasshopper.Femurandtibiaarelong.Legsaresuitedfor
walking.
Scansorial:(Scansorial=Climbing;climbingorclingingleg)
e.g.allthethreepairsoflegsofheadlouse.

8. REFERENCES:
Introduction:
https://wiki.bugwood.org/Insect_Biology
https://wiki.bugwood.org/File:Insect_legs.jpg
https://genent.cals.ncsu.edu/bug-bytes/thorax/legs/
Structureoftypicalinsectlegs:
https://www.slideshare.net/ARUN5218/insect-legs-and-its-modifications
TYPESOFINSECT’SLEGS:
https://wwwthedragonflywoman.com/2010/12/10/insect-legs/
https://slideplayer.com/slide/4419531/
https://genent.cals.ncsu.edu/wp-content/themes/salient/img/labs/cursorial.jpg
https://genent.cals.ncsu.edu/wp-content/themes/salient/img/extanat/prolegs.gif