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Insect legs and it's modifications
- 1. Insect legs and it's modifications IMRAN UL HASSAN SOLANGI Session 2019-20 Department of Zoology Shah Abdul Latif University (SALU) Khairpur
- 2. CONTENT Introduction of Insects of legs Structure of typical insect legs TYPES OF INSECTS LEGS Saltatorial jumping Raptorial seizing Fossorial digging Natatorial swimming Cursorial running Scansoria --- Climbing Ambulatorial --- walking
- 3. Insect Legs:- Insect have three pairs of legs, one pair on each of the three segments of the thorax and are generally called the fore-, mid-, and hind legs. Any of the pairs of legs may be heavily modified and are important for locomotion, prey capture, mating, etc. Thankfully, just like mouthparts, all insect legs contain the same basic parts. From proximal (toward or against the body) to distal (away from the body) the parts of an insect leg are: coxa, trochanter, femur, tibia, and tarsus. The tarsus almost always has one or two claws at the type used to grasp the substrate. The figure Insect Legs, right, shows legs modified for numerous purposes: A, running; B, jumping; C, digging; D, grasping; E, catching; F, walking and digging; G, reduced leg used for walking and digging; H, male leg modified for grasping females during mating. Abdominal Prolegs Some insect larvae, such as caterpillars, have pairs of short fleshy legs on one or more abdominal segments. These legs may have tiny hooks or barbs (called crochets) that serve to grip the substrate. Abdominal prolegs never occur in an insects adult stage. They are a unique larval adaptation derived from a completely different embryological origin than the thoracic legs.
- 4. Structure of typical insect legs Consist of 5 segments namely Coxa , trochanter, femur , tibia and tarsus .Tarsus consist of 1-5 small segments called tarsomeres.Last tarsomere bears a pair of claws A pad between the claws is called Arolium Pads at the base of claws are called pulvilli. While the legs are normally adapted for walking many insects have them modified for variety of functions.Various modifications are Saltatorial legs Hind legs adapted for leaping of jumping . The femur is greatly enlarged giving articulation for large muscles of tibia which are used in jumping occur in Grasshopper,Cricket. The term pretarsus refers to the terminal segment of the tarsus and any other structures attached to it, including: ungues a pair of claws arolium a lobe or adhesive pad between the claws empodium a large bristle (or lobe) between the claws pulvilli a pair of adhesive pads
- 5. TYPES OF INSECTS LEGS Saltatorial jumping Raptorial seizing Fossorial digging Natatorial swimming Cursorial running Scansoria --- Climbing Ambulatorial --- walking Saltatorial: (Salatorial = Leaping : Jumping Leg) Saltatorial legs are jumping legs. Youve all seen these kinds of legs before! Grasshoppers are the poster insects for saltatorial legs, but other jumping insects like fleas have them as well. Saltatorial legs work well for jumping because they are enlarged legs filled with bulky, strong muscles. All those muscles allow insects with this type of leg to jump, propelling themselves forward very long distances very quickly. Saltatorial legs are usually hind legs. e.g. hind leg of grasshopper. Raptorial: (Raptorial = predatory ; Grasping leg) You are likely familiar with this sort of leg too. Raptorial legs are hunting legs, the kinds of legs you see on predatory insects such as mantids and giant water bugs. Like the saltatorial legs, these are enlarged legs full of strong, powerful muscles. However, these legs are usually at the front of the insect and are used to grab and hold prey while they eat. Many insects with raptorial legs hold them out in front of their bodies, positioned so that they can strike at prey at any time. e.g. Forelegs of preying mantis.
- 6. Fossorial: (Fossorial = Digging; Burrowing leg) Insects with fossorial legs live underground and use their highly modified legs, usually the forelegs, to dig burrows. The mole cricket, the forlegs of which are pictured at left, are a prime example. Fossorial legs tend to be very broad, very flat, and very dense. They often have big, strong claws. Fossorial legs work somewhat like shovels to rip soils apart quickly and easily and allow the insect to bury itself in the ground surprisingly quickly. This type of leg is much less common than the others, but its a thrill to find an insect that has them! Theyre really impressive. e.g. Fore legs of mole cricket. Natatorial: (Natatorial = pertaining to swimming; Swimming leg) Natatorial is another word for swimming, so insects with natatorial legs are aquatic insects that require modified legs to move easily through water. Natatorial legs are often flattened, broad, and fringed with dense hairs, as in the image of the predaceous diving beetle hind leg pictured at right. These adaptations have the same sort of effect as a human wearing flippers as they swim they increase the surface area of the legs as they kick, allowing the insect to move more easily through water. Many aquatic insects exhibit natatorial legs, especially in the hind and middle pairs of legs, but not all of them do. They are especially common in aquatic beetles and bugs. e.g. hing legs of water bug and water beetle.
- 7. Cursorial: (Cursorial = adapted for running : Running leg) These are the types of legs most people likely think of if theyve ever pondered insect legs before. Cursorial is a fancy word for running, so these are the kinds of legs you see on swiftly moving insects such as roaches and tiger beetles. Cursorial legs tend to be long and narrow and are designed so that the insect can move very quickly. Things with this type of leg are often hard to catch or hard to step on if youre dealing with roaches. e.g. All the three pairs of legs of cockroach. Legs are suited for running. Femur is not swollen. Ambulatorial (Ambulate - to walk; Walking leg) e.g. Fore leg and middle leg of grasshopper. Femur and tibia are long. Legs are suited for walking. Scansorial: (Scansorial = Climbing; climbing or clinging leg) e.g. all the three pairs of legs of head louse.
- 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/ Structure of typical insect legs: /ARUN5218/insect-legs-and-its-modifications TYPES OF INSECTS LEGS: 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