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56-409: Whiskers are sensitive tactile hairs that aid navigation, locomotion, exploration, hunting, social touch and perform other functions. This article is primarily about the specialised sensing hairs of mammals, but some birds, fish, insects , crustaceans and other arthropods are known to have similar structures also used to sense the environment. Vibrissae (from Latin vibrāre 'to vibrate') from

112-500: A brain and a ventral nerve cord . Most insects reproduce by laying eggs . Insects breathe air through a system of paired openings along their sides, connected to small tubes that take air directly to the tissues. The blood therefore does not carry oxygen; it is only partly contained in vessels, and some circulates in an open hemocoel . Insect vision is mainly through their compound eyes , with additional small ocelli . Many insects can hear, using tympanal organs , which may be on

168-451: A family of catfishes (order Siluriformes) commonly known as the long-whiskered catfishes. Anurognathid pterosaurs had a rugose (wrinkled) jaw texture that has been interpreted as the attachment sites for vibrissae, though actual vibrissae have not been recorded. More recently, a specific type of feathers has been found around anurognathid mouths. Insect Insects (from Latin insectum ) are hexapod invertebrates of

224-423: A common ancestor of all therian mammals . Indeed, some humans even still develop vestigial vibrissal muscles in the upper lip, consistent with the hypothesis that previous members of the human lineage had mystacial vibrissae. Thus, it is possible that the development of the whisker sensory system played an important role in mammalian development, more generally. Researchers have begun to build artificial whiskers of

280-438: A cyclic way, tracing small circles at their tips. This motion, called "whisking" can occur at speeds of 25 Hz in mice, which is one of the fastest movements that mammals can make. Small animals use whisking to position their front paws during locomotion. Vibrissae typically grow in clusters. These groups vary somewhat in form and function, but they are relatively consistent among land mammals. Between land and marine mammals, there

336-525: A dog following a scent trail, and even to discriminate the species and the size of the fish responsible for the trail. Blind ringed seals have even been observed successfully hunting on their own in Lake Saimaa , likely relying on their vibrissae to gain sensory information and catch prey. Unlike terrestrial mammals, such as rodents , pinnipeds do not move their vibrissae over an object when examining it but instead extend their moveable whiskers and keep them in

392-552: A hundred species, are marine. Insects such as snow scorpionflies flourish in cold habitats including the Arctic and at high altitude. Insects such as desert locusts , ants, beetles, and termites are adapted to some of the hottest and driest environments on earth, such as the Sonoran Desert . Insects form a clade , a natural group with a common ancestor, among the arthropods . A phylogenetic analysis by Kjer et al. (2016) places

448-401: A large group of land and marine mammals (see images), and it is this group that has received by far the most scientific study. The arrangement of these whiskers is not random: they form an ordered grid of arcs (columns) and rows, with shorter whiskers at the front and longer whiskers at the rear (see images). In the mouse, gerbil, hamster, rat, guinea pig, rabbit, and cat, each individual follicle

504-618: A nearly immobile pupa . Insects that undergo three-stage metamorphosis lack a pupa, developing through a series of increasingly adult-like nymphal stages. The higher level relationship of the insects is unclear. Fossilized insects of enormous size have been found from the Paleozoic Era, including giant dragonfly-like insects with wingspans of 55 to 70 cm (22 to 28 in). The most diverse insect groups appear to have coevolved with flowering plants . Adult insects typically move about by walking and flying; some can swim. Insects are

560-680: A period of weeks by whisker trimming (they soon grow back), or for the duration of an experimental trial by restraining the whiskers with a flexible cover like a mask (the latter technique is used, in particular, in studies of marine mammals). Such experiments have shown that whiskers are required for, or contribute to: object localization, orienting of the snout, detection of movement, texture discrimination, shape discrimination, exploration, thigmotaxis , locomotion, maintenance of equilibrium, maze learning, swimming, locating food pellets, locating food animals, and fighting, as well as nipple attachment and huddling in rat pups. Whisking—the periodic movement of

616-422: A sensation in the brain only after information about the stimulus travels there via afferent nerve pathways. Afferent is derived from Latin participle afferentem ( af - = ad -  : to + ferre  : bear, carry), meaning carrying into , whereas efferent is derived from ex ferens , meaning carrying away (e- = ex- means 'from'). Ad and ex give an mnemonic device for remembering

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672-505: A similar way to cats. Other birds that have obvious "whiskers" are kiwis , flycatchers , swallows , nightjars , whip-poor-wills , the kākāpō and the long-whiskered owlet ( Xenoglaux loweryi ). Some fish have slender, pendulous tactile organs near the mouth. These are often referred to as "whiskers", although they are more correctly termed barbels . Fish that have barbels include the catfish, carp, goatfish, hagfish, sturgeon, zebrafish and some species of shark. The Pimelodidae are

728-461: A slightly larger number of microvibrissae. Thus, an estimate for the total number of sensory nerve cells serving the mystacial vibrissal array on the face of a rat or mouse might be 25,000. Natural shapes of rat's mystacial pad vibrissae are well approximated by pieces of the Euler spiral . When all these pieces for a single rat are assembled together, they span an interval extending from one coiled domain of

784-423: A swelling in the dorsal root known as the dorsal root ganglion . All of the axons in the dorsal root, which contains afferent nerve fibers, are used in the transduction of somatosensory information. Somatosensory receptors include senses such as pain, touch, temperature, itch, and stretch. For example, a specific muscle fiber called an intrafusal muscle fiber is a type of afferent neuron that lies parallel to

840-509: A variety of types, both to help them understand how biological whiskers work and as a tactile sense for robots. These efforts range from the abstract, through feature-specific models, to attempts to reproduce complete whiskered animals in robot form (ScratchBot and ShrewBot, both robots by Bristol Robotics Laboratory). A range of non-mammals possess structures which resemble or function similarly to mammalian whiskers. Some birds possess specialized hair-like feathers called rictal bristles around

896-525: A variety of ways. Male moths can sense the pheromones of female moths over great distances. Other species communicate with sounds: crickets stridulate , or rub their wings together, to attract a mate and repel other males. Lampyrid beetles communicate with light. Humans regard many insects as pests , especially those that damage crops, and attempt to control them using insecticides and other techniques. Others are parasitic , and may act as vectors of diseases . Insect pollinators are essential to

952-561: Is genetically determined and does not vary as the cat grows thinner or fatter. In the laboratory, rats are able to accurately (within 5–10%) discriminate the size of an opening, so it seems likely that cats can use their whiskers for this purpose. However, reports of cats, particularly kittens, with their heads firmly stuck in some discarded receptacle are commonplace indicating that if a cat has this information available, it does not always make best use of it. Pinnipeds have well-developed tactile senses. Their mystacial vibrissae have ten times

1008-445: Is innervated by 100–200 primary afferent nerve cells . These cells serve an even larger number of mechanoreceptors of at least eight distinct types. Accordingly, even small deflections of the vibrissal hair can evoke a sensory response in the animal. Rats and mice typically have approximately 30 macrovibrissae on each side of the face, with whisker lengths up to around 50 mm in (laboratory) rats, 30 mm in (laboratory) mice, and

1064-567: Is less consistency (though commonalities are certainly present). Many land mammals, like rats and hamsters, have four typical whisker groups on their heads (called cranial vibrissae ), which might vary among animals due to different lifestyles. These cranial groups include: The mystacial whiskers can be roughly identified as macrovibrissae (long whiskers for feeling the space around the head) and microvibrissae (small, down-pointing whiskers for identifying objects). Not only are these two types hard to distinguish on an animal's face (see for example

1120-830: The Latin word insectum from in , "cut up", as insects appear to be cut into three parts. The Latin word was introduced by Pliny the Elder who calqued the Ancient Greek word ἔντομον éntomon "insect" (as in entomology ) from ἔντομος éntomos "cut in pieces"; this was Aristotle 's term for this class of life in his biology , also in reference to their notched bodies. The English word insect first appears in 1601 in Philemon Holland 's translation of Pliny. In common speech, insects and other terrestrial arthropods are often called bugs . Entomologists to some extent reserve

1176-2337: The Paraneoptera , and Kjer et al. 2016 for the Holometabola . The numbers of described extant species (boldface for groups with over 100,000 species) are from Stork 2018. Archaeognatha (hump-backed/jumping bristletails, 513 spp) [REDACTED] Zygentoma (silverfish, firebrats, fishmoths, 560 spp) [REDACTED] Odonata (dragonflies and damselflies, 5,899 spp) [REDACTED] Ephemeroptera (mayflies, 3,240 spp) [REDACTED] Zoraptera (angel insects, 37 spp) [REDACTED] Dermaptera (earwigs, 1,978 spp) [REDACTED] Plecoptera (stoneflies, 3,743 spp) [REDACTED] Orthoptera (grasshoppers, crickets, katydids, 23,855 spp) [REDACTED] Grylloblattodea (ice crawlers, 34 spp) [REDACTED] Mantophasmatodea (gladiators, 15 spp) [REDACTED] Phasmatodea (stick insects, 3,014 spp) [REDACTED] Embioptera (webspinners, 463 spp) [REDACTED] Mantodea (mantises, 2,400 spp) [REDACTED] Blattodea (cockroaches and termites, 7,314 spp) [REDACTED] Psocodea (book lice, barklice and sucking lice, 11,000 spp) [REDACTED] [REDACTED] Hemiptera (true bugs, 103,590 spp) [REDACTED] Thysanoptera (thrips, 5,864 spp) [REDACTED] Hymenoptera (sawflies, wasps, bees, ants, 116,861 spp) [REDACTED] Strepsiptera (twisted-wing flies, 609 spp) [REDACTED] Coleoptera (beetles, 386,500 spp) [REDACTED] Raphidioptera (snakeflies, 254 spp) [REDACTED] Neuroptera (lacewings, 5,868 spp) [REDACTED] Megaloptera (alderflies and dobsonflies, 354 spp) [REDACTED] Lepidoptera (butterflies and moths, 157,338 spp) [REDACTED] Trichoptera (caddisflies, 14,391 spp) [REDACTED] Diptera (true flies, 155,477 spp) [REDACTED] Mecoptera (scorpionflies, 757 spp) [REDACTED] Siphonaptera (fleas, 2,075 spp) [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] Afferent nerve fiber Afferent nerve fibers are axons (nerve fibers) of sensory neurons that carry sensory information from sensory receptors to

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1232-504: The brain of whisker-specialist mammals is involved in the processing of nerve impulses from vibrissae, a fact that presumably corresponds to the important position the sense occupies for the animal. Information from the vibrissae arrives in the brain via the trigeminal nerve and is delivered first into the trigeminal sensory complex of brainstem . From there, the most studied pathways are those leading up through parts of thalamus and into barrel cortex , though other major pathways through

1288-430: The brainstem . The second order neuron's projection decussates at the medulla through medial lemniscus to the third order neurons in the thalamus . The third order neuron's axon terminates at the primary somatosensory cortex of the parietal lobe . Types of afferent fibers include the general somatic , the general visceral , the special somatic and the special visceral afferent fibers . Alternatively, in

1344-422: The central nervous system . Many afferent projections arrive at a particular brain region. In the peripheral nervous system , afferent nerve fibers are part of the sensory nervous system and arise from outside of the central nervous system. Sensory and mixed nerves contain afferent fibers. Afferent neurons are pseudounipolar neurons that have a single process leaving the cell body dividing into two branches:

1400-439: 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 jointed legs , compound eyes , and a pair of antennae . Insects are the most diverse group of animals, with more than a million described species ; they represent more than half of all animal species. The insect nervous system consists of

1456-439: The extrafusal muscle fibers thus functions as a stretch receptor by detecting muscle length. All of these sensations travel along the same general pathways towards the brain. One pathway— dorsal column–medial lemniscus pathway —begins with sensation from the periphery being sent via afferent nerve fiber of the dorsal root ganglion (first order neuron) through the spinal cord to the dorsal column nuclei (second order neuron) in

1512-436: The innervation of terrestrial mammals, allowing them to effectively detect vibrations in the water. These vibrations are generated, for example, when a fish swims through water. Detecting vibrations is useful when the animals are foraging and may add to or even replace vision, particularly in darkness. Harbor seals have been observed following varying paths of other organisms that swam ahead several minutes before, similar to

1568-404: The sensory system , afferent fibers can be classified by sizes with category specifications depending on if they innervate the skins or muscles. In the nervous system , there is a "closed loop" system of sensation, decision, and reactions. This process is carried out through the activity of sensory neurons, interneurons , and motor neurons . A touch or painful stimulus, for example, creates

1624-602: The superior colliculus in midbrain (a major visual structure in visual animals) and the cerebellum , to name but a couple, are increasingly coming under scrutiny. Neuroscientists, and other researchers, studying sensory systems favour the whisker system for a number of reasons (see Barrel cortex ), not least the simple fact that laboratory rats and mice are whisker, rather than visual, specialists. The presence of mystacial vibrissae in distinct lineages ( Rodentia , Afrotheria , marsupials ) with remarkable conservation of operation suggests that they may be an old feature present in

1680-588: The Euler spiral to the other. Marine mammals may make even greater investment in their vibrissal sensory system than rats and mice. Seal whiskers, which are similarly arrayed across the mystacial region, are each served by around 10 times as many nerve fibres as those in rats and mice, so that the total number of nerve cells innervating the mystacial vibrissae of a seal has been estimated to be in excess of 300,000. Manatees, remarkably, have around 600 vibrissae on or around their lips. Whiskers can be very long in some species;

1736-618: The Hemiptera (true bugs), Lepidoptera (butterflies and moths), Diptera (true flies), Hymenoptera (wasps, ants, and bees), and Coleoptera (beetles), each with more than 100,000 described species. Insects are distributed over every continent and almost every terrestrial habitat. There are many more species in the tropics , especially in rainforests , than in temperate zones. The world's regions have received widely differing amounts of attention from entomologists. The British Isles have been thoroughly surveyed, so that Gullan and Cranston 2014 state that

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1792-561: The animal. Likely benefits are that it provides more degrees of freedom for sensor positioning, that it allows the animal to sample a larger volume of space with a given density of whiskers, and that it allows control over the velocity with which the whiskers contact surfaces. Animals that do not whisk, but have motile whiskers, presumably also gain some advantage from the investment in musculature. Dorothy Souza, in her book Look What Whiskers Can Do reports some whisker movement during prey capture (in cats, in this case): Whiskers bend forward as

1848-488: The base of the beak which are sometimes referred to as whiskers. The whiskered auklet ( Aethia pygmaea ) has striking, stiff white feathers protruding from above and below the eyes of the otherwise slate-grey bird, and a dark plume which swoops forward from the top of its head. Whiskered auklets sent through a maze of tunnels with their feathers taped back bumped their heads more than twice as often as they did when their feathers were free, indicating they use their feathers in

1904-486: The body hairs of the Florida manatee may be a vibrissa (see image). Other marine mammals, like seals and sea-lions, have head vibrissae just like those on land mammals (see image), although these groups function quite differently . Vibrissal follicles have evolved other functions in dolphins, such as electroreception . The vibrissal hair is usually thicker and stiffer than other types of (pelagic) hair but, like other hairs,

1960-448: The cat pounces. Teeth grasp the mouse tightly around its neck. The cat holds on until the prey stops wriggling. Anecdotally, it is often stated that cats use their whiskers to gauge whether an opening is wide enough for their body to pass through. This is sometimes supported by the statement that the whiskers of individual cats extend out to about the same width as the cat's body, but at least two informal reports indicate that whisker length

2016-563: The characteristic motion seen in a small rodent that is otherwise sitting still. In medicine, the term also refers to the thick hairs found inside human nostrils . The last common ancestor of all extant mammals had vibrissae. All other extant mammal species besides great apes retain the same ancestral layout of the whiskers along with the special facial muscles that move them. Vibrissae are anatomically distinguished from other hair. They are easily visually identified since they are longer, stiffer, significantly larger in diameter, and stand above

2072-443: The head and body. Generally, vibrissae are considered to mediate a tactile sense, complementary to that of skin. This is presumed to be advantageous in particular to animals that cannot always rely on sight to navigate or to find food, for example, nocturnal animals or animals which forage in muddy waters. Whiskers can also function as wind detecting antannae such as the supra-orbital ones in rats. Sensory function aside, movements of

2128-773: The image of a rat here), there are similarly weak distinctions in how they are used, though the distinction is nonetheless referred to ubiquitously in scientific literature and is considered useful in analysis. Many land mammals, including domestic cats, also have vibrissae on the underside of the leg just above the paws (called carpal vibrissae ). Whilst these five major groups are often reported in studies of land mammals, several other groups have been reported more occasionally; for instance nasal , angular , and submental whiskers . Marine mammals can have substantially different arrangements of their vibrissae. For instance, whales and dolphins have lost their snout whiskers and gained vibrissae around their blowholes, whereas every single one of

2184-592: The insects among the Hexapoda , six-legged animals with segmented bodies; their closest relatives are the Diplura (bristletails). Collembola (springtails) [REDACTED] Protura (coneheads) [REDACTED] Diplura (two-pronged bristletails) [REDACTED] Insecta (=Ectognatha) [REDACTED] The internal phylogeny is based on the works of Wipfler et al. 2019 for the Polyneoptera , Johnson et al. 2018 for

2240-406: The legs or other parts of the body. Their sense of smell is via receptors, usually on the antennae and the mouthparts. Nearly all insects hatch from eggs . Insect growth is constrained by the inelastic exoskeleton, so development involves a series of molts . The immature stages often differ from the adults in structure, habit and habitat. Groups that undergo four-stage metamorphosis often have

2296-459: The length of a chinchilla 's whiskers can be more than a third of its body length (see image). Even in species with shorter whiskers, they can be very prominent appendages (see images). Thus, whilst whiskers certainly could be described as "proximal sensors" in contrast to, say, eyes, they offer a tactile sense with a sensing range that is functionally very significant. The follicles of some groups of vibrissae in some species are motile . Generally,

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2352-409: The long one towards the sensory organ , and the short one toward the central nervous system (e.g. spinal cord). These cells do have sensory afferent dendrites , similar to those typically inherent in neurons . They have a smooth and rounded cell body located in the ganglia of the peripheral nervous system. Just outside the spinal cord , thousands of afferent neuronal cell bodies are aggregated in

2408-460: The macrovibrissae together. Amongst those species with motile macrovibrissae, some (rats, mice, flying squirrels, gerbils, chinchillas, hamsters, shrews, porcupines, opossums) move them back and forth periodically in a movement known as whisking , while other species (cats, dogs, raccoons, pandas) do not appear to. The distribution of mechanoreceptor types in the whisker follicle differs between rats and cats, which may correspond to this difference in

2464-402: The name "bugs" for a narrow category of " true bugs ", insects of the order Hemiptera , such as cicadas and shield bugs . Other terrestrial arthropods, such as centipedes , millipedes , woodlice , spiders , mites and scorpions , are sometimes confused with insects, since they have a jointed exoskeleton. Adult insects are the only arthropods that ever have wings, with up to two pairs on

2520-554: The only invertebrates that can achieve sustained powered flight; insect flight evolved just once. Many insects are at least partly aquatic , and have larvae with gills; in some species, the adults too are aquatic. Some species, such as water striders , can walk on the surface of water. Insects are mostly solitary, but some, such as bees , ants and termites , are social and live in large, well-organized colonies . Others, such as earwigs , provide maternal care, guarding their eggs and young. Insects can communicate with each other in

2576-466: The relationship between afferent and efferent  : a fferent connection a rrives and an e fferent connection e xits . Another mnemonic device used for remembering afferent and efferent (in terms of the spinal cord, with its dorsal/ventral organization) is SAME DAVE. Sensory Afferent Motor Efferent, Dorsal Afferent Ventral Efferent. Afferent and efferent are connected to affect and effect through their common Latin roots: afferent nerves affect

2632-535: The reproduction of many flowering plants and so to their ecosystems. Many insects are ecologically beneficial as predators of pest insects, while a few provide direct economic benefit. Two species in particular are economically important and were domesticated many centuries ago: silkworms for silk and honey bees for honey . Insects are consumed as food in 80% of the world's nations, by people in roughly 3000 ethnic groups. Human activities are having serious effects on insect biodiversity . The word insect comes from

2688-618: The same position. By holding their vibrissae steady, pinnipeds are able to maximize their detection ability. The vibrissae of seals are undulated and wavy while sea lion and walrus vibrissae are smooth. Research is ongoing to determine the function, if any, of these shapes on detection ability. The vibrissa's angle relative to the flow, and not the fiber shape, however, seems to be the most important factor. Most cetaceans have whiskers at birth but they are typically lost during maturation. The follicles and any vestigial hair sometimes function as touch or electrical sense organs. A large part of

2744-428: The shaft consists of an inert material ( keratin ) and contains no nerves . However, vibrissae are different from other hair structures because they grow from a special hair follicle incorporating a capsule of blood called a blood sinus which is heavily innervated by sensory nerves. Vibrissae are symmetrically arranged in groups on the face and supply the trigeminal nerve. The mystacial macrovibrissae are shared by

2800-420: The supraorbital, genal and macrovibrissae are motile, whereas the microvibrissae are not. This is reflected in anatomical reports that have identified musculature associated with the macrovibrissae that is absent for the microvibrissae. A small muscle 'sling' is attached to each macrovibrissa and can move it more-or-less independently of the others, whilst larger muscles in the surrounding tissue move many or all of

2856-404: The surrounding fur by a considerable amount. In addition, they have well-innervated follicles , and an identifiable representation in the somatosensory cortex of the brain. The largest number and the longest are found among the small, social, arboreal, and nocturnal mammals. Whiskers of aquatic mammals are the most sensitive. During foraging in complex, dark habitats, whiskers are rapidly moved in

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2912-527: The thorax. Whether winged or not, adult insects can be distinguished by their three-part body plan, with head, thorax, and abdomen; they have three pairs of legs on the thorax. Estimates of the total number of insect species vary considerably, suggesting that there are perhaps some 5.5 million insect species in existence, of which about one million have been described and named. These constitute around half of all eukaryote species, including animals , plants , and fungi . The most diverse insect orders are

2968-518: The total of around 22,500 species is probably within 5% of the actual number there; they comment that Canada's list of 30,000 described species is surely over half of the actual total. They add that the 3000 species of the American Arctic must be broadly accurate. In contrast, a large majority of the insect species of the tropics and the southern hemisphere are probably undescribed. Some 30–40,000 species inhabit freshwater ; very few insects, perhaps

3024-412: The vibrissae may also indicate something of the state of mind of the animal, and the whiskers play a role in social behaviour of rats. The sensory function of vibrissae is an active research area—experiments to establish the capabilities of whiskers use a variety of techniques, including temporary deprivation either of the whisker sense or of other senses. Animals can be deprived of their whisker sense for

3080-422: The way they are used. Whisking movements are amongst the fastest produced by mammals. In all whisking animals in which it has so far been measured, these whisking movements are rapidly controlled in response to behavioural and environmental conditions. The whisking movements occur in bouts of variable duration, and at rates between 3 and 25 whisks/second. Movements of the whiskers are closely coordinated with those of

3136-451: The whiskers—is also presumed to serve tactile sensing in some way. However, exactly why an animal might be driven "to beat the night with sticks", as one researcher once put it, is a matter of debate, and the answer is probably multi-faceted. Scholarpedia offers: Since rapid movement of the vibrissae consumes energy, and has required the evolution of specialised musculature, it can be assumed that whisking must convey some sensory advantages to

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