what does it depend on, how did they appear from the point of view of evolution and how are different types of mandibles useful in ants?

• Discussion post on Reddit from 3 years ago about why humans, as opposed to other hominids, evolved flat faces
• One user hypothesizes that the primate lineage as a whole had an evolutionary tendency of reducing the face bones’ length, possibly due to the omnivore diet and living style
• Another user suggests that the shift to cooked food allowed for smaller jaws, but the canines also shrunk dramatically, suggesting a shift in aggressive displays away from the teeth; the flatness of the face overall may also relate to the use of speech and non-verbal communication by the face
• A third user proposes the wild speculation that humans developed a facial structure that is more capable of “taking a punch,” as an adaptation to inter-species competition
• Another user suggests that elongated jaws generally allow for musculature attachments, which allow for greater bite force, but humans did not require that bite force, so they did not maintain elongated jaws
• One user speculates that the neotenous (youthful) features of the human face, compared to other primates, might be a sex-selection-driven feature, especially for women, where youth is more precious than it is in men
• Some users suggest that the flatness of the human face might have something to do with lateralization of the hemispheres of the brain. Flatness of the face may also relate to the use of speech and non-verbal communication by the face; smaller facial muscles with finer control and a smaller, quicker mouth to form words and talk. The development of the chin remains a mystery
• A user notes that some monkeys, such as marmosets, also have flat faces, which suggests that there is no insurmountable pressure to evolve long pointed faces in primates
• One user suggests that the flatter face of humans may relate to cultural evolution
• One user notes that the human hand is quite strong for a primate hand, especially in the form of a fist, which might be related to reduced aggression involving the teeth
• Hominids with larger brains grew a larger rear half of the skull but not long mandibles, which remained relatively short even if human brains were shrunk to chimpanzee size
• Some primates have elongated mandibles and very deep-set eyes, but they still retain stereoscopic vision
• The disappearance of elongated jaws and the appearance of chins in humans remains a mystery
• The original statement of the question was corrected: not all hominids

• Insect mandibles are a pair of appendages near the insect’s mouth, and they are the most anterior of the three pairs of oral appendages.
• Mandibles are typically used to grasp, crush, or cut the insect’s food, or to defend against predators or rivals.
• Insect mandibles appear to be evolutionarily derived from legs, move in the horizontal plane and are used unlike those of vertebrates, which appear to be derived from gill arches and move vertically.
• The mouthparts of orthopteran insects are often used as a basic example of mandibulate (chewing) mouthparts, and the mandibles themselves are likewise generalized in structure.
• Grasshoppers, crickets, and other simple insects have large and hardened mandibles, shaped like pinchers, with cutting surfaces on the distal portion and chewing or grinding surfaces basally. They are usually lined with teeth and move sideways. Large pieces of leaves can, therefore, be cut and then pulverized near the mouth opening.
• The mandibles of adult and larval Odonata are simple and generalized, although there are typically six or seven mandibular muscles. Ephemeroptera rarely feeds as adults, though the nymphs have simple mandibles.
• Stag beetle with mandibles modified no longer used in feeding. Nearly all adult beetles, and many beetle larvae, have mandibles. In general form they are similar to those of grasshoppers: hardened and tooth-like.
• Certain firefly larvae that feed on snails have grooved mandibles that not only physically break down their prey but also deliver digestive fluids by these grooves. Ground beetles have long mandibles that project far in front of them, which aid them in feeding on snails inside their shells.
• Members of the stag beetle family have greatly enlarged mandibles that are often forked, resembling the horns of various deer, from which their common name comes, and similar modifications appear in various scarab beetles and longhorn beetles. Males of these beetles use their mandibles to grasp or displace each other as they compete for mates.
• The Hemiptera, and other insects whose mouthparts are described as piercing-sucking, have modified mandibles. Rather than being tooth-like, the mandibles of such insects are lengthened into stylets, which form the outer two parts of the feeding tube, or beak. Most hemipterans feed on plants, using their sucking and piercing mouthparts to extract plant sap

• The shape of an ant’s head, mandibles, and size of the eyes can reveal its diet and lifestyle.
• Different types of ants have different mandibles depending on their function such as multi-purpose, piercing the skin of large predators, crushing hard seeds, hunting insect prey, slicing leaves like scissors, grasping millipedes and capturing quick insects, blocking the nest entrance, etc.
• The typical ant has triangular mandibles with short pointy teeth used for multiple purposes.
• Army ant soldier (Eciton) has hooked mandibles with sharp blades that pierce the skin of larger predators.
• Big-headed ant major (Pheidole) has heavy and blunt mandibles powered by a muscular head used for crushing hard seeds.
• Bull-dog ants (Myrmecia) have huge bulging eyes with excellent vision used for hunting insect prey.
• Leafcutter ant (Atta) has powerful mandibles used for slicing leaves like scissors.
• Marvelous ant (Thaumatomyrmex) has pitchfork mandibles used to grasp millipedes covered with long bristles and strip them off before eating.
• Trap-jaw ant (Odontomachus) hunts with its mandibles locked wide open and snaps them shut in a fast and powerful snap up to 145 miles per hour. They capture springtails and other quick insects.
• Turtle ant major (Cephalotes) has an armored disc covering the front of its head used for blocking the nest entrance and preventing enemies from entering.
• The closing of trap-jaw ant mandibles is one of the fastest movements in the animal kingdom.
• The mandibles of ants have evolved over time to best fit their lifestyle and diet.
• Ants are important to the ecosystem as pollinators and as predators to other insects.
• Leafcutter ants use vegetation to grow fungus, which is their only source of food, and are considered the farmers of the ant world.
• The website has a printable ant head summary and an ant head match game that can be downloaded.

• Researchers have discovered that the Dracula ant, Mystrium camillae, can snap its mandibles closed at 90 meters per second (>200 mph), making it the fastest animal movement on record.
• The ants use their powerful mandibles to stun prey before transporting them back to the nest to feed their larvae.
• The study analyzed the ant’s mandibles and found that they are uniquely shaped to support the rapid snap-jaw movement.
• The mandibles have a unique locking mechanism that helps the ant resist the forces it generates during the snap motion.
• The study’s authors suggest that the snap-jaw motion in Dracula ants may be a precursor to the trap-jaw motion seen in other ant species.
• Trap-jaw ants use their jaws for a similar stunning effect but also use them to launch themselves through the air.
• Similarly to Dracula ants, trap-jaw ants have evolved specialized mandibles.
• The article includes a link to the abstract for the study mentioned in the article.
• A commenter on Reddit provides a link to the abstract and comments on how the snap-jaw mechanics are specialized for high-speed power amplification in Dracula ants.
• Another commenter responds to the claim that Dracula ants have the fastest animal movement on record, noting that the peregrine falcon has a higher top speed (240 mph) but obtains it through gravity assist.

1. Mandibles are central to ant biology. Ants use their mandibles for an array of activities, such as manipulation of objects, food processing, hunting and defense. Unlike other social insects, they have cooperative brood care, where eggs and larvae are directly handled by attending workers.
2. Ant mandibles are characterised by outer, external margins and internal margins that are divided by a basal angle into basal and masticatory margins that bear teeth and denticles. Ants primitively had short, curved mandibles with two teeth, but some modern ants have basically this same mandibular morphology, although usually with additional teeth.
3. Thorns, allusions, knives, and spears are a few of the many different shapes ant mandibles can take depending on their needs. Some ants have elongated mandibles, lacking noticeable teeth except at the apices, while others have mandibles with triangular shapes. Some ants have mandibles that are highly specialized for offense or defense, for example, the sickle-like mandibles of the Polyergus, which are used to kill defending ants, and the trap-jaw mechanisms in certain ant genera used to capture prey.
4. Mandibles can be used to pin down prey or grasp prey until a paralyzing sting can be delivered. Some ants use their mandibles as weapons or tools that can facilitate their hunting success. However, most ants lack painful bites, being too small to have any effect on human skin.
5. The text notes that although inverted mandibles have evolved in some ant groups, they are rare. It implies that the mandibular diversity in ants evolved through natural selection.
6. The primitive condition in ants has 6-segmented maxillary palpi and 4-segmented labial palpi, but this number decreases during the evolution of various ant lineages. In addition, in some ants, palp articles have become greatly elongated.
7. On the whole, ants have evolved a wide variety of mandible shapes that allow them to fulfill their different needs.

• Ants use their mandibles for almost any task, including prey-catching, fighting, leaf-cutting, brood care, and communication.
• The key to the versatility of mandible functions is the mandible closer muscle.
• In ants, this muscle is generally composed of distinct muscle fiber types that differ in morphology and contractile properties.
• Fast contracting fibers have short sarcomeres (2-3 micrometers) and attach directly to the closer apodeme, which conveys the muscle power to the mandible joint.
• Slow but forceful contracting fibers have long sarcomeres (5-6 micrometers) and attach to the apodeme either directly or via thin thread-like filaments.
• The volume proportions of the fiber types are species-specific and correlate with feeding habits.
• Two biomechanical models explain why species that rely on fast mandible strikes, such as predatory ants, have elongated head capsules that accommodate long muscle fibers directly attached to the apodeme at small angles. In contrast, species that depend on forceful movements, like leaf-cutting ants, have broader heads and many filament-attached fibers.
• Trap-jaw ants feature highly specialized catapult mechanisms. Their mandible closing is known as one of the fastest movements in the animal kingdom.
• The relatively large number of motor neurons that control the mandible closer reflects the importance of this muscle for the behavior of ants as well as other insects.

Similar articles:

• Gronenberg et al. (1997) found that different types of muscle fibers in ant mandibles differ in their contractile properties, with fast fibers having higher shortening velocities and force output capacities than slow fibers.
• Paul and Gronenberg (1999) investigated how mandible muscle fibers can optimize force and velocity in ants.
• Larabee et al. (2017) investigated the performance, morphology, and control of power-amplified mandibles in the trap-jaw ant Myrmoteras.
• Fitts and Widrick (1996) reviewed the adaptations of muscle mechanics to exercise training.
• Murray et al. (2001) reviewed the role of the human lateral pterygoid muscle in the control of horizontal jaw movements.

Cited by:

• Dejean et al. (2023) investigated an Old World leaf-cutting, fungus-growing ant as a case of convergent evolution.
• Püffel et al. (2023) created a biomechanical model for the relation between bite force and mandibular opening angle in

• Title of the webpage: “Thaumatomyrnex ant, whose jaws are used to literally shred the string like defense on a paralyzed polyxenida millepede using sharp teeth on the end of its mandibles”
• In the image, the Thaumatomyrnex ant is seen feeding on a pincushion millipede or polyxenida millepede.
• The pincushion millipede’s body is covered with toxic, barbed spines that make it nearly untouchable by any other predators.
• Polyxenida millepede can actually fling the barbs at a potential attacker.
• The Thaumatomyrnex ant has mandibles that are specialized to work through the defenses of this formidable target. The sharp teeth on the end of its mandibles literally shred the string-like defense (toxic hairs) of the paralyzed pincushion millipede so that it can feed without being harmed by the toxic spines.
• The mandibles of the Thaumatomyrnex ant are pointed, curved, and sharp-edged.
• A reddit user comments “This ant is 100% specialized in working through all the defenses of this formidable target that generally nothing else in the Amazon will go near. In the image you can see that the ant has stripped all the dangerous barbs from the millipede’s left side so it can feed without risk.”
• Another Reddit user comments, “I want to know how it [Thaumatomyrnex ant] paralyzes the prey before it takes off the toxic hairs.”
• There are no links or references to external sources that could provide further information on the topic.

Not used in article

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The role of mandibles in ant defense mechanisms

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The function of mandibles in feeding behavior and how they evolved

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The 3 common types of mandibles in ants with brief descriptions