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Insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of ...
mandibles are a pair of appendages near the insect's mouth, and the most anterior of the three pairs of oral appendages (the
labrum Labrum Latin, defined as "having the edge" * Labrum (architecture), a large water-filled vessel or basin with an overhanging lip * Labrum (arthropod mouthpart), a flap-like structure in front of the mouth in almost all extant Euarthropoda * Bron ...
is more anterior, but is a single fused structure). Their function is typically to grasp, crush, or cut the insect's food, or to defend against predators or rivals. Insect mandibles, which appear to be evolutionarily derived from legs, move in the horizontal plane unlike those of vertebrates, which appear to be derived from gill arches and move vertically.


Grasshoppers, crickets, and other simple insects

The mouthparts of
orthoptera Orthoptera () is an order of insects that comprises the grasshoppers, locusts, and crickets, including closely related insects, such as the bush crickets or katydids and wētā. The order is subdivided into two suborders: Caelifera – grasshop ...
n insects are often used as a basic example of mandibulate (chewing) mouthparts, and the mandibles themselves are likewise generalized in structure. They are large and hardened, shaped like pinchers, with cutting surfaces on the
distal Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
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 specific derived morphology of the teeth on the mandible varies depending on whether the insect eats broad-leafed herbs or grasses. This same simple structure is seen in all of the remaining
Polyneoptera The cohort Polyneoptera is a proposed taxonomic ranking for the Orthoptera (grasshoppers, crickets, etc.) and all other Neopteran insects believed to be more closely related to Orthoptera than to any other insect orders. These winged insects, n ...
n insect orders, with the exception of the
Paraneoptera Paraneoptera or Acercaria is a superorder of insects which includes lice ( bark lice and true lice), thrips, and hemipterans, the true bugs. It also includes the extinct order Permopsocida, known from fossils dating from the Early Permian to t ...
(
Hemiptera Hemiptera (; ) is an order of insects, commonly called true bugs, comprising over 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, assassin bugs, bed bugs, and shield bugs. They range in size from to aroun ...
,
Thysanoptera Thrips ( order Thysanoptera) are minute (mostly long or less), slender insects with fringed wings and unique asymmetrical mouthparts. Different thrips species feed mostly on plants by puncturing and sucking up the contents, although a few are ...
, and
Phthiraptera Louse ( : lice) is the common name for any member of the clade Phthiraptera, which contains nearly 5,000 species of wingless parasitic insects. Phthiraptera has variously been recognized as an order, infraorder, or a parvorder, as a result o ...
). The mandibles of adult and larval
Odonata Odonata is an order of flying insects that includes the dragonflies and damselflies. Members of the group first appeared during the Triassic, though members of their total group, Odonatoptera, first appeared in Late Carboniferous. The two commo ...
appear simple and generalized, although there are typically six or seven mandibular muscles. Ephemeroptera rarely feed as adults, though the
nymphs A nymph ( grc, νύμφη, nýmphē, el, script=Latn, nímfi, label=Modern Greek; , ) in ancient Greek folklore is a minor female nature deity. Different from Greek goddesses, nymphs are generally regarded as personifications of nature, are typ ...
have simple mandibles.


True bugs

The
Hemiptera Hemiptera (; ) is an order of insects, commonly called true bugs, comprising over 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, assassin bugs, bed bugs, and shield bugs. They range in size from to aroun ...
, 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. The mandibles are therefore instrumental in piercing the plant or animal tissues upon which these insects feed, and in helping draw up fluids to the insect's mouth. Most hemipterans feed on plants, using their sucking and piercing mouthparts to extract plant sap. Some are hematophagous, while others are predators that feed on other insects or small invertebrates. They live in a wide variety of habitats, generally terrestrial, though some species are adapted to life in or on the surface of fresh water.


Beetles

Nearly all adult
beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...
s, and many beetle larvae, have mandibles. In general form they are similar to those of grasshoppers: hardened and tooth-like. Beetle mandibles show a remarkable amount of variability between species, and some are very highly adapted to the food sources or other uses that the species has for them. Certain
firefly The Lampyridae are a family of elateroid beetles with more than 2,000 described species, many of which are light-emitting. They are soft-bodied beetles commonly called fireflies, lightning bugs, or glowworms for their conspicuous production ...
larvae (family Lampyridae) that feed on snails have grooved mandibles that not only physically break down their prey, but also deliver digestive fluids by these grooves.
Ground beetle Ground beetles are a large, cosmopolitan family of beetles, the Carabidae, with more than 40,000 species worldwide, around 2,000 of which are found in North America and 2,700 in Europe. As of 2015, it is one of the 10 most species-rich animal fam ...
s (family Carabidae) of the tribe Cychrini 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 Stag beetles are a family of about 1,200 species of beetles in the family Lucanidae, currently classified in four subfamilies.Smith, A.B.T. (2006). A review of the family-group names for the superfamily Scarabaeoidea (Coleoptera) with corrections ...
family (Lucanidae) have greatly enlarged mandibles that are often forked, resembling the horns of various
deer Deer or true deer are hoofed ruminant mammals forming the family Cervidae. The two main groups of deer are the Cervinae, including the muntjac, the elk (wapiti), the red deer, and the fallow deer; and the Capreolinae, including the rei ...
, from which their common name comes, and similar modifications appear in various
scarab beetles The family Scarabaeidae, as currently defined, consists of over 30,000 species of beetles worldwide; they are often called scarabs or scarab beetles. The classification of this family has undergone significant change in recent years. Several sub ...
and
longhorn beetle The longhorn beetles (Cerambycidae), also known as long-horned or longicorns, are a large family of beetles, with over 35,000 species described. Most species are characterized by extremely long antennae, which are often as long as or longer than ...
s. Males of these beetles use their mandibles to grasp or displace each other as they compete for mates. The largest of all
families Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Ideall ...
, the
Curculionidae The Curculionidae are a family of weevils, commonly called snout beetles or true weevils. They are one of the largest animal families, with 6,800 genera and 83,000 species described worldwide. They are the sister group to the family Brentidae. ...
(weevils), with some 83,000 member species, belongs to this order. Found in almost every habitat except the sea and the
polar region The polar regions, also called the frigid zones or polar zones, of Earth are the regions of the planet that surround its geographical poles (the North and South Poles), lying within the polar circles. These high latitudes are dominated by floa ...
s, they interact with their
ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syst ...
s in several ways: beetles often feed on plants and
fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from t ...
, break down animal and plant debris, and eat other
invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
s. Some species are serious agricultural pests, such as the
Colorado potato beetle The Colorado potato beetle (''Leptinotarsa decemlineata''), also known as the Colorado beetle, the ten-striped spearman, the ten-lined potato beetle, or the potato bug, is a major pest of potato crops. It is about long, with a bright yellow/o ...
, while others such as
Coccinellidae Coccinellidae () is a widespread family of small beetles ranging in size from . They are commonly known as ladybugs in North America and ladybirds in Great Britain. Some entomologists prefer the names ladybird beetles or lady beetles as they ...
(ladybirds or ladybugs) eat
aphid Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...
s,
scale insect Scale insects are small insects of the order Hemiptera, suborder Sternorrhyncha. Of dramatically variable appearance and extreme sexual dimorphism, they comprise the infraorder Coccomorpha which is considered a more convenient grouping than the ...
s,
thrips Thrips ( order Thysanoptera) are minute (mostly long or less), slender insects with fringed wings and unique asymmetrical mouthparts. Different thrips species feed mostly on plants by puncturing and sucking up the contents, although a few are ...
, and other plant-sucking insects that damage crops.


Lice

The mandibles in
Phthiraptera Louse ( : lice) is the common name for any member of the clade Phthiraptera, which contains nearly 5,000 species of wingless parasitic insects. Phthiraptera has variously been recognized as an order, infraorder, or a parvorder, as a result o ...
(lice) are also modified into piercing stylets. Chewing lice live among the hairs or feathers of their host and feed on skin and debris, while sucking lice pierce the host's skin and feed on blood and other secretions. They usually spend their whole life on a single host, cementing their eggs, called nits, to hairs or feathers. The eggs hatch into
nymphs A nymph ( grc, νύμφη, nýmphē, el, script=Latn, nímfi, label=Modern Greek; , ) in ancient Greek folklore is a minor female nature deity. Different from Greek goddesses, nymphs are generally regarded as personifications of nature, are typ ...
, which moult three times before becoming fully grown, a process that takes about four weeks.


Thrips

Thysanoptera Thrips ( order Thysanoptera) are minute (mostly long or less), slender insects with fringed wings and unique asymmetrical mouthparts. Different thrips species feed mostly on plants by puncturing and sucking up the contents, although a few are ...
(
thrips Thrips ( order Thysanoptera) are minute (mostly long or less), slender insects with fringed wings and unique asymmetrical mouthparts. Different thrips species feed mostly on plants by puncturing and sucking up the contents, although a few are ...
) have a variation of piercing mouthparts. During development they lose one mandible, so only the left mandible is present, modified into a stylet.


Neuropteroids

Within the
Neuropterida The Neuropterida are a clade, sometimes placed at superorder level, of holometabolous insects with over 5,700 described species, containing the orders Neuroptera (lacewings, antlions), Megaloptera (alderflies, dobsonflies), and Raphidioptera (sn ...
, adults have chewing mouthparts, but the mandibles of male
dobsonflies Dobsonflies are a subfamily of insects, Corydalinae, part of the Megalopteran family Corydalidae. The larvae (commonly called hellgrammites) are aquatic, living in streams, and the adults are often found along streams as well. The nine genera o ...
are non-functional in feeding. The larvae in many lineages are predatory, with mandibles modified with grooves along which digestive saliva flows, while the larvae of the family
Sisyridae Sisyridae, commonly known as spongeflies or spongillaflies, are a family of winged insects in the order Neuroptera. There are approximately 60 living species described, and several extinct species identified from the fossil record. Description ...
have the mouthparts developed into a sucking tube which they use to feed on the liquid tissues of freshwater
sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through ...
s.


Ants, bees, and wasps

Most adult
Hymenoptera Hymenoptera is a large order of insects, comprising the sawflies, wasps, bees, and ants. Over 150,000 living species of Hymenoptera have been described, in addition to over 2,000 extinct ones. Many of the species are parasitic. Females typic ...
have mandibles that follow the general form, as in grasshoppers. The mandibles are used to clip pieces of vegetation, gather wood fibers, dig nests, or to capture and disassemble prey. What is unusual is that many Hymenoptera have the remaining mouthparts modified to form a
proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elong ...
(a "tongue" used to feed on liquids), making them virtually the only insects that normally possess both chewing mouthparts ''and'' sucking mouthparts (a few exceptional members of other orders may exhibit this, such as flower-feeding beetles that also have "tongues"). '' Trigona corvina'', and other stingless bees, utilize their mandibles for defense purposes and typically interlock them with other individuals while fighting for resources.


Flies

Several families of
flies Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...
, notably
mosquito Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small flies within the family Culicidae (from the Latin ''culex'' meaning "gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish for "litt ...
es (family Culicidae), have mandibles that are modified into stylets for piercing, similar to the true bugs. Flies of the
Muscomorpha The Brachyceran infraorder Muscomorpha is a large and diverse group of flies, containing the bulk of the Brachycera, and, most of the known flies. It includes a number of the most familiar flies, such as the housefly, the fruit fly, and the blo ...
, including the
house fly The housefly (''Musca domestica'') is a fly of the suborder Cyclorrhapha. It is believed to have evolved in the Cenozoic Era, possibly in the Middle East, and has spread all over the world as a commensal of humans. It is the most common fly ...
, ''Musca domestica'',
stable fly ''Stomoxys calcitrans'' is commonly called the stable fly, barn fly, biting house fly, dog fly, or power mower fly. Unlike most members of the family Muscidae, ''Stomoxys calcitrans'' ('sharp mouth' + 'kicking') and others of its genus suck bl ...
, ''Stomoxys calcitrans'',
blow flies The Calliphoridae (commonly known as blow flies, blow-flies, carrion flies, bluebottles, greenbottles, or cluster flies) are a family of insects in the order Diptera, with almost 1,900 known species. The maggot larvae, often used as fishing ba ...
(family Calliphoridae), and many others, lack mandibles altogether, and the mouthparts are designed for sponging up liquids.


Butterflies and moths

All but a few adult
Lepidoptera Lepidoptera ( ) is an order of insects that includes butterflies and moths (both are called lepidopterans). About 180,000 species of the Lepidoptera are described, in 126 families and 46 superfamilies, 10 percent of the total described specie ...
lack mandibles, with the remaining mouthparts forming an elongated sucking tube. The exception is the mandibulate moths (family Micropterigidae), which have fully developed mandibles as adults.


See also

*
Insect mouthparts Insects have mouthparts that may vary greatly across insect species, as they are adapted to particular modes of feeding. The earliest insects had chewing mouthparts. Most specialisation of mouthparts are for piercing and sucking, and this mode o ...
*
Yellow jacket Yellowjacket or yellowjacket is the common name in North America for predatory social wasps of the genera ''Vespula'' and '' Dolichovespula''. Members of these genera are known simply as "wasps" in other English-speaking countries. Most of these ...
*
Grasshopper Grasshoppers are a group of insects belonging to the suborder Caelifera. They are among what is possibly the most ancient living group of chewing herbivorous insects, dating back to the early Triassic around 250 million years ago. Grasshoppe ...


References


External links


The evolution of animal weapons
{{DEFAULTSORT:Mandible (Insect) Insect anatomy