In evolutionary biology, parasitism is a relationship between species, where one organism, the parasite, lives on or in another organism, the host, causing it some harm, is adapted structurally to this way of life. The entomologist E. O. Wilson has characterised parasites as "predators that eat prey in units of less than one". Parasites include protozoans such as the agents of malaria, sleeping sickness, amoebic dysentery. There are six major parasitic strategies of exploitation of animal hosts, namely parasitic castration, directly transmitted parasitism, trophically transmitted parasitism, vector-transmitted parasitism and micropredation. Like predation, parasitism is a type of consumer-resource interaction, but unlike predators, with the exception of parasitoids, are much smaller than their hosts, do not kill them, live in or on their hosts for an extended period. Parasites of animals are specialised, reproduce at a faster rate than their hosts. Classic examples include interactions between vertebrate hosts and tapeworms, the malaria-causing Plasmodium species, fleas.
Parasites reduce host fitness by general or specialised pathology, from parasitic castration to modification of host behaviour. Parasites increase their own fitness by exploiting hosts for resources necessary for their survival, in particular by feeding on them and by using intermediate hosts to assist in their transmission from one definitive host to another. Although parasitism is unambiguous, it is part of a spectrum of interactions between species, grading via parasitoidism into predation, through evolution into mutualism, in some fungi, shading into being saprophytic. People have known about parasites such as roundworms and tapeworms since ancient Egypt and Rome. In Early Modern times, Antonie van Leeuwenhoek observed Giardia lamblia in his microscope in 1681, while Francesco Redi described internal and external parasites including sheep liver fluke and ticks. Modern parasitology developed in the 19th century. In human culture, parasitism has negative connotations; these were exploited to satirical effect in Jonathan Swift's 1733 poem "On Poetry: A Rhapsody", comparing poets to hyperparasitical "vermin".
In fiction, Bram Stoker's 1897 Gothic horror novel Dracula and its many adaptations featured a blood-drinking parasite. Ridley Scott's 1979 film Alien was one of many works of science fiction to feature a terrifying parasitic alien species. First used in English in 1539, the word parasite comes from the Medieval French parasite, from the Latin parasitus, the latinisation of the Greek παράσιτος, "one who eats at the table of another" and that from παρά, "beside, by" + σῖτος, "wheat", hence "food"; the related term parasitism appears in English from 1611. Parasitism is a kind of symbiosis, a close and persistent long-term biological interaction between a parasite and its host. Unlike commensalism and mutualism, the parasitic relationship harms the host, either feeding on it or, as in the case of intestinal parasites, consuming some of its food; because parasites interact with other species, they can act as vectors of pathogens, causing disease. Predation is by definition not a symbiosis, as the interaction is brief, but the entomologist E. O. Wilson has characterised parasites as "predators that eat prey in units of less than one".
Within that scope are many possible strategies. Taxonomists classify parasites in a variety of overlapping schemes, based on their interactions with their hosts and on their life-cycles, which are sometimes complex. An obligate parasite depends on the host to complete its life cycle, while a facultative parasite does not. Parasite life-cycles involving only one host are called "direct". An endoparasite lives inside the host's body. Mesoparasites - like some copepods, for example - enter an opening in the host's body and remain embedded there; some parasites can be generalists, feeding on a wide range of hosts, but many parasites, the majority of protozoans and helminths that parasitise animals, are specialists and host-specific. An early basic, functional division of parasites distinguished macroparasites; these each had a mathematical model assigned in order to analyse the population movements of the host–parasite groupings. The microorganisms and viruses that can reproduce and complete their life cycle within the host are known as microparasites.
Macroparasites are the multicellular organisms that reproduce and complete their life cycle outside of the host or on the host's body. Much of the thinking on types of parasitism has focussed on terrestrial animal parasites of animals, such as helminths; those in other environments and with other hosts have analogous strategies. For example, the snubnosed eel is a facultative endoparasite that opportunistically burrows into and eats sick and dying fish. Plant-eating insects such as scale insects and caterpillars resemble ectoparasites, attacking much larger plants; as female scale-insects cannot move, they are obligate parasites, permanently attached to their hosts. There are six major parasitic strategies, namely parasitic castration, directly transmitted parasitism, trophically transmitted parasitism, vector-transmitted parasitism, parasitoid
Androlaelaps casalis known as Haemolaelaps casalis is a species of predatory mite that feeds on other mites and small invertebrates. It cannot bite or sting birds and humans because its mandibles are not designed for sucking but for predation on other mites; because Androlaelaps casalis mites feed off parasitic mites like Dermanyssus gallinae, individuals with red colored abdomens can be found. This is not due to any blood-sucking by A. casalis but is because it has ingested blood-engorged parasitic mites. There is some evidence that it may be associated with dermatitis in humans
An allergen is a type of antigen that produces an abnormally vigorous immune response in which the immune system fights off a perceived threat that would otherwise be harmless to the body. Such reactions are called allergies. In technical terms, an allergen is an antigen, capable of stimulating a type-I hypersensitivity reaction in atopic individuals through Immunoglobulin E responses. Most humans mount significant Immunoglobulin E responses only as a defense against parasitic infections. However, some individuals may respond to many common environmental antigens; this hereditary predisposition is called atopy. In atopic individuals, non-parasitic antigens stimulate inappropriate IgE production, leading to type I hypersensitivity. Sensitivities vary from one person to another. A broad range of substances can be allergens to sensitive individuals. Allergens can be found in a variety of sources, such as dust mite excretion, pet dander, or royal jelly. Food allergies are not as common as food sensitivity, but some foods such as peanuts, nuts and shellfish are the cause of serious allergies in many people.
The United States Food and Drug Administration does recognize eight foods as being common for allergic reactions in a large segment of the sensitive population. These include peanuts, tree nuts, milk, fish and their derivatives, soy and their derivatives, as well as sulfites at 10ppm and over. See the FDA website for complete details. Other countries, in view of the differences in the genetic profiles of their citizens and different levels of exposure to specific foods due to different dietary habits, the "official" allergen list will change. Canada recognizes all eight of the allergens recognized by the US, recognizes sesame seeds, mustard; the European Union additionally recognizes other gluten-containing cereals as well as celery and lupin. Another allergen is urushiol, a resin produced by poison ivy and poison oak, which causes the skin rash condition known as urushiol-induced contact dermatitis by changing a skin cell's configuration so that it is no longer recognized by the immune system as part of the body.
Various trees and wood products such as paper, cardboard, MDF etc. can cause mild to severe allergy symptoms through touch or inhalation of sawdust such as asthma and skin rash. An allergic reaction can be caused by any form of direct contact with the allergen—consuming food or drink one is sensitive to, breathing in pollen, perfume or pet dander, or brushing a body part against an allergy-causing plant. Other common causes of serious allergy are wasp, fire ant and bee stings and latex. An serious form of an allergic reaction is called anaphylaxis. One form of treatment is the administration of sterile epinephrine to the person experiencing anaphylaxis, which suppresses the body's overreaction to the allergen, allows for the patient to be transported to a medical facility. In addition to foreign proteins found in foreign serum and vaccines, common allergens include: Animal products Fel d 1 fur and dander cockroach calyx wool dust mite excretion Drugs penicillin sulfonamides salicylates Foods celery and celeriac corn or maize eggs fruit pumpkin, egg-plant legumes beans peas peanuts soybeans milk seafood sesame soy tree nuts pecans almonds wheat Insect stings bee sting venom wasp sting venom mosquito stings Mold spores Top 5 allergens discovered in patch tests in 2005–06: nickel sulfate Balsam of Peru fragrance mix I quaternium-15, neomycin.
Metals Nickel Chromium Other latex wood Plant pollens grass — ryegrass, timothy-grass weeds — ragweed, nettle, Artemisia vulgaris, Chenopodium album, sorrel trees — birch, hazel, Aesculus, poplar, Tilia, Ashe juniper, Alstonia scholaris Seasonal allergy symptoms are experienced during specific parts of the year during spring, summer or fall when certain trees or grasses pollinate. This depends on the kind of grass. For instance, some trees such as oak and maple pollinate in the spring, while grasses such as Bermuda and orchard pollinate in the summer. Grass allergy is linked to hay fever because their symptoms and causes are somehow similar to each other. Symptoms include rhinitis, which causes sneezing and a runny nose, as well as allergic conjunctivitis, which includes watering and itchy eyes. An initial tickle on the roof of the mouth or in the back of the throat may be experienced. Depending on the season, the symptoms may be more severe and people may experience coughing and irritability.
A few people become depressed, lose their appetite, or have problems sleeping. Moreover, since the sinuses may become congested, some people experience headaches. If both parents suffered from allergies in the past, there is a 66% chance for the individual to suffer from seasonal allergies, the risk lowers to 60% if just one parent had suffered from allergies; the immune system has strong influence on seasonal allergies, since it reacts differently to diverse allergens like pollen. When an allergen enters the body of an individual, predisposed to allergies, it triggers an immune reaction and the production of antibodies; these allergen antibodies migrate to mast cells lining the nose and lungs. When an allergen drifts into the nose more than once, mast cells release a slew of chemicals or histamines that irritate and inflame the moist membranes lining the nose and produ
In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and all descendants of that ancestor excluding a few—typically only one or two—monophyletic subgroups. The group is said to be paraphyletic with respect to the excluded subgroups; the arrangement of the members of a paraphyletic group is called a paraphyly. The term is used in phylogenetics and in linguistics; the term was coined to apply to well-known taxa like Reptilia which, as named and traditionally defined, is paraphyletic with respect to mammals and birds. Reptilia contains the last common ancestor of reptiles and all descendants of that ancestor—including all extant reptiles as well as the extinct synapsids—except for mammals and birds. Other recognized paraphyletic groups include fish and lizards. If many subgroups are missing from the named group, it is said to be polyparaphyletic. A paraphyletic group cannot be a clade, or monophyletic group, any group of species that includes only a common ancestor and all of its descendants.
Formally, a paraphyletic group is the relative complement of one or more subclades within a clade: removing one or more subclades leaves a paraphyletic group. The term paraphyly, or paraphyletic, derives from the two Ancient Greek words παρά, meaning "beside, near", φῦλον, meaning "genus, species", refers to the situation in which one or several monophyletic subgroups of organisms are left apart from all other descendants of a unique common ancestor. Conversely, the term monophyly, or monophyletic, builds on the Ancient Greek prefix μόνος, meaning "alone, unique", refers to the fact that a monophyletic group includes organisms consisting of all the descendants of a unique common ancestor. By comparison, the term polyphyly, or polyphyletic, uses the Ancient Greek prefix πολύς, meaning "many, a lot of", refers to the fact that a polyphyletic group includes organisms arising from multiple ancestral sources. Groups that include all the descendants of a common ancestor are said to be monophyletic.
A paraphyletic group is a monophyletic group from which one or more subsidiary clades are excluded to form a separate group. Ereshefsky has argued that paraphyletic taxa are the result of anagenesis in the excluded group or groups. A group whose identifying features evolved convergently in two or more lineages is polyphyletic. More broadly, any taxon, not paraphyletic or monophyletic can be called polyphyletic; these terms were developed during the debates of the 1960s and 1970s accompanying the rise of cladistics. Paraphyletic groupings are considered problematic by many taxonomists, as it is not possible to talk about their phylogenetic relationships, their characteristic traits and literal extinction. Related terminology that may be encountered are stem group, budding cladogenesis, anagenesis, or'grade' groupings. Paraphyletic groups are a relic from previous erroneous assessments about phylogenic relationships, or from before the rise of cladistics; the prokaryotes, because they exclude the eukaryotes, a descendant group.
Bacteria and Archaea are prokaryotes, but archaea and eukaryotes share a common ancestor, not ancestral to the bacteria. The prokaryote/eukaryote distinction was proposed by Edouard Chatton in 1937 and was accepted after being adopted by Roger Stanier and C. B. van Niel in 1962. The botanical code abandoned consideration of bacterial nomenclature in 1975. Among plants, dicotyledons are paraphyletic. "Dicotyledon" has not been used as an ICBN classification for decades, but is allowed as a synonym of Magnoliopsida. Phylogenetic analysis indicates. Excluding monocots from the dicots makes the latter a paraphyletic group. Among animals, several familiar groups are not, in fact, clades; the order Artiodactyla is paraphyletic. In the ICZN Code, the two taxa are orders of equal rank. Molecular studies, have shown that the Cetacea descend from artiodactyl ancestors, although the precise phylogeny within the order remains uncertain. Without the Cetacean descendants the Artiodactyls must be paraphyletic; the class Reptilia as traditionally defined is paraphyletic because it excludes mammals.
In the ICZN Code, the three taxa are classes of equal rank. However, mammals hail from the synapsids and birds are descended from the dinosaurs, both of which are reptiles. Alternatively, reptiles are paraphyletic. Birds and reptiles together make Sauropsids. Osteichthyes, bony fish, are paraphyletic when they include only Actinopterygii and Sarcopterygii, excluding tetrapods; the wasps are paraphyletic, consisting of the narrow-waisted Apocrita without the bees. The sawflies are paraphyletic, forming all of the Hymenoptera except for the Apocrita, a clade deep within the sawfly tree. Crustaceans are not a clade; the modern clade that spans all of them is the Tetraconata. Species have a special status in systematics as being an observable feature of nature itself and a
Demodex is a genus of tiny mites that live in or near hair follicles of mammals. Around 65 species of Demodex are known. Two species live on humans: Demodex folliculorum and Demodex brevis, both referred to as eyelash mites. Different species of animals host different species of Demodex. Demodex canis lives on the domestic dog. Infestation with Demodex is common and does not cause any symptoms, although some skin diseases can be caused by the mites. Demodex is derived from Greek δημός dēmos "fat" and δήξ dēx, "woodworm". D. folliculorum and D. brevis are found on humans. D. folliculorum was first described in 1842 by Simon. D. folliculorum is found in hair follicles, while D. brevis lives in sebaceous glands connected to hair follicles. Both species are found in the face - near the nose, the eyelashes, eyebrows, but occur elsewhere on the body; the adult mites are only 0.3–0.4 mm long, with D. brevis shorter than D. folliculorum. Each has a elongated body that consists of two fused segments. Eight short, segmented legs are attached to the first body segment.
The body is covered with scales for anchoring itself in the hair follicle, the mite has pin-like mouthparts for eating skin cells and oils which accumulate in the hair follicles. The mites can leave the hair follicles and walk around on the skin, at a speed of 8–16 mm per hour at night, as they try to avoid light; the mites are transferred between hosts through contact with hair and the sebaceous glands of the face. Females of D. folliculorum are rounder than males. Both male and female Demodex mites have a genital opening, fertilization is internal. Mating takes place in the follicle opening, eggs are laid inside the hair follicles or sebaceous glands; the six-legged larvae hatch after 3-4 days, the larvae develop into adults in about 7 days. The total lifespan of a Demodex mite is several weeks. Older people are much more to carry the mites; the lower rate in children may be. A study of 29 adults in North Carolina, US, found that 70% of those under 18 years of age carried mites, that all adults over 18 carried them.
This study, along with several studies of cadavers, suggests that previous work might have underestimated the mites' prevalence. However, the small sample size and small geographical area involved prevent drawing broad conclusions from these data. Demodex mites are now considered parasitic. However, in the vast majority of cases, the mites go unobserved without any adverse symptoms, though in certain cases, mite populations can increase; this results in a condition known as demodicosis or Demodex mite bite, characterised by itching and other skin disorders. Blepharitis can be caused by Demodex mites. Research about human infection by Demodex mites is ongoing: Evidence of a correlation between Demodex infection and acne vulgaris exists, suggesting it might play a role in promoting acne. Several preliminary studies suggest an association between mite rosacea; the natural host of D. canis is the domestic dog. Although it can temporarily infect humans, D. canis mites cannot survive on the human skin, so die shortly after exposure and are considered not to be zoonotic.
The D. canis mite has a commensal relationship with the dog and under normal conditions does not produce any clinical signs or disease. The escalation of a commensal D. canis infestation into one requiring clinical attention involves complex immune factors. Under normal health conditions, the mite can live within the dermis of the dog without causing any harm to the animal. However, whenever an immunosuppressive condition is present and the dog's immune system is compromised, it allows the mites to proliferate; as they continue to infest the host, clinical signs begin to become apparent and demodicosis/demodectic mange/red mange is diagnosed. Demodicosis can manifest as lesions of two types: squamous, which causes dry alopecia and thickening of the skin, pustular, the more severe form, causing secondary infection, resulting in the characteristic numerous red pustules and wrinkling of the skin. Demodicosis can follow immunosuppressive conditions or treatments, or may be related to a genetic immune deficiency.
Certain breeds, such as the Dalmatian, the American Bulldog, the American Pit Bull Terrier—appear to be more susceptible. Since D. canis is a part of the natural fauna on a canine's skin, the mite is not considered to be contagious. All dogs receive an initial exposure from their mothers during nursing; the immune system of the animal under most all healthy conditions keeps the population of the mite in check, so subsequent exposure to dogs possessing clinical demodectic mange does not increase an animal's chance of developing demodicosis. Since demodicosis is the result of an immune deficiency, subsequent infestations after treatment can occur. 16. Shipstone, Michael. "Antiparasitics for Integumentary Disease: Ivermectin," http://www.merckvetmanual.com/pharmacology/systemic-pharmacotherapeutics-of-the-integumentary-system/antiparasitics-for-integum
Arachnids are a class of joint-legged invertebrate animals, in the subphylum Chelicerata. All adult arachnids have eight legs, although the front pair of legs in some species has converted to a sensory function, while in other species, different appendages can grow large enough to take on the appearance of extra pairs of legs; the term is derived from the Greek word ἀράχνη, from the myth of the hubristic human weaver Arachne, turned into a spider. Spiders are the largest order in the class, which includes scorpions, mites and solifuges. In 2019, a molecular phylogenetic study placed horseshoe crabs in Arachnida. All extant arachnids are terrestrial, living on land. However, some inhabit freshwater environments and, with the exception of the pelagic zone, marine environments as well, they comprise over 100,000 named species. All adult arachnids have eight legs, arachnids may be distinguished from insects by this fact, since insects have six legs. However, arachnids have two further pairs of appendages that have become adapted for feeding and sensory perception.
The first pair, the chelicerae, serve in defense. The next pair of appendages, the pedipalps, have been adapted for feeding, and/or reproductive functions. In Solifugae, the palps are quite leg-like; the larvae of mites and Ricinulei have only six legs. However, mites are variable: as well as eight, there are adult mites with six or four legs. Arachnids are further distinguished from insects by the fact, their body is organized into two tagmata, called the prosoma, or cephalothorax, the opisthosoma, or abdomen. The cephalothorax is derived from the fusion of the cephalon and the thorax, is covered by a single, unsegmented carapace; the abdomen is segmented in the more primitive forms, but varying degrees of fusion between the segments occur in many groups. It is divided into a preabdomen and postabdomen, although this is only visible in scorpions, in some orders, such as the Acari, the abdominal sections are fused. A telson is present in scorpions, where it has been modified to a stinger, in the Schizomida, whip scorpions and Palpigradi.
Like all arthropods, arachnids have an exoskeleton, they have an internal structure of cartilage-like tissue, called the endosternite, to which certain muscle groups are attached. The endosternite is calcified in some Opiliones. Most arachnids lack extensor muscles in the distal joints of their appendages. Spiders and whipscorpions extend their limbs hydraulically using the pressure of their hemolymph. Solifuges and some harvestmen extend their knees by the use of elastic thickenings in the joint cuticle. Scorpions and some harvestmen have evolved muscles that extend two leg joints at once; the equivalent joints of the pedipalps of scorpions though, are extended by elastic recoil. There are characteristics that are important for the terrestrial lifestyle of arachnids, such as internal respiratory surfaces in the form of tracheae, or modification of the book gill into a book lung, an internal series of vascular lamellae used for gas exchange with the air. While the tracheae are individual systems of tubes, similar to those in insects, ricinuleids and some spiders possess sieve tracheae, in which several tubes arise in a bundle from a small chamber connected to the spiracle.
This type of tracheal system has certainly evolved from the book lungs, indicates that the tracheae of arachnids are not homologous with those of insects. Further adaptations to terrestrial life are appendages modified for more efficient locomotion on land, internal fertilisation, special sensory organs, water conservation enhanced by efficient excretory structures as well as a waxy layer covering the cuticle; the excretory glands of arachnids include up to four pairs of coxal glands along the side of the prosoma, one or two pairs of Malpighian tubules, emptying into the gut. Many arachnids have the other type of excretory gland, although several do have both; the primary nitrogenous waste product in arachnids is guanine. Arachnid blood is variable in composition, depending on the mode of respiration. Arachnids with an efficient tracheal system do not need to transport oxygen in the blood, may have a reduced circulatory system. In scorpions and some spiders, the blood contains haemocyanin, a copper-based pigment with a similar function to haemoglobin in vertebrates.
The heart is located in the forward part of the abdomen, may or may not be segmented. Some mites have no heart at all. Arachnids are carnivorous, feeding on the pre-digested bodies of insects and other small animals. Only in the harvestmen and among mites, such as the house dust mite, is there ingestion of solid food particles, thus exposure to internal parasites, although it is not unusual for spiders to eat their own silk. Several groups secrete venom from specialized glands to kill prey or enemies. Several mites and ticks are parasites. Arachnids produce digestive juices in their stomachs, use their pedipalps and chelicerae to pour them over their dead prey; the digestive juices turn the prey into a broth of nutrients, which the arachnid sucks into a pre-buccal cavity located in front of the mouth. Behind the mouth is a muscular, sclerotised pharynx, which acts as a pump, sucking the food through the mouth and on into the oesophagus and stomach. In some arachnids, the oesophagus a
Trombiculidae are a family of mites. The best known of the Trombiculidae are the chiggers; the two recognized definitions of "chigger" are the scientific and the common, the latter of which can be found in English and medical dictionaries. According to most dictionaries, the several species of Trombiculidae that bite their host in their larval stage and cause "intense irritation" or "a wheal with severe itching and dermatitis", are called chiggers; the scientific definition includes many more, but not all species of Trombiculidae. Trombiculidae live in forests and grasslands and are found in the vegetation of low, damp areas such as woodlands, berry bushes, along lakes and streams, in drier places where vegetation is low, such as lawns, golf courses, parks, they are most numerous in early summer when grass and other vegetation are heaviest. In their larval stage, they attach to various animals, including humans, feed on skin causing itching; these relatives of ticks are nearly microscopic, have a chrome-orange hue.
There is a marked constriction in the front part of the body in the adult stages. The best known species of chigger in North America is the hard-biting Trombicula alfreddugesi of the southeastern United States, humid Midwest and Mexico. Trombiculid mites go through a lifecycle of egg, larva and adult; the larval mites feed on the skin cells of animals. The six-legged parasitic larva feeds on a large variety of creatures, including humans, toads, box turtles and some insects. After crawling onto their hosts, they inject digestive enzymes into the skin that break down skin cells, they do not "bite", but instead form a hole in the skin called a stylostome and chew up tiny parts of the inner skin, thus causing severe irritation and swelling. The severe itching is accompanied by red, pimple-like bumps or hives and skin rash or lesions on a sun-exposed area. For humans, itching occurs after the larvae detach from the skin. After feeding on their hosts, the larvae drop to the ground and become nymphs mature into adults which have eight legs and are harmless to humans.
In the postlarval stage, they feed on plant material. The females lay three to eight eggs in a clutch on a leaf or under the roots of a plant, die by autumn. Trombiculidae, from Greek τρομειν and Latin culex, genitive culicis, was first described as an independent family by Henry Ellsworth Ewing in 1944; when the family was first described, it included two subfamilies, Hemitrombiculinae and Trombiculinae. Womersley added another, which at the time contained only Leeuwenhoekia, he erected the family Leeuwenhoekiidae for the genus and subfamily, having six genera. References to chiggers, however, go as far back as sixth-century China, by 1733, the first recognition of trombiculid mites in North America was made. In 1758, Carl Linnaeus described a single species, Acarus batatas. However, most information about chiggers came from problems that arose during and after World War II. Trombiculid mites are found throughout the world. In Europe and North America, they tend to be more prevalent in the humid regions.
In the more temperate regions, they are found only during the summer. In the United States, they are found in the southeast, the south, the Midwest, they are not present, or found, in far northern areas, high mountains, deserts. In the British Isles, the species Trombicula autumnalis is called harvest mites, in North America the species Trombicula alfreddugesi, the species Trombicula hirsti which are found in Australia and are called the scrub-itch mite; the length of the mite's cycle depends on species and environment but lasts two to 12 months. The number of cycles in a year depends on the region. For example, in a temperate region, there might only be three per year, but in tropical regions the cycle might be continuous all year long. Adult harvest mites winter in protected places such as below the soil. Females become active in the spring, once the ground temperature is above 60 °F, she lays eggs in vegetation, up to 15 eggs per day; the eggs are round and are dormant for about six days, after which the nonfeeding prelarvae emerge, with only three pairs of legs.
After about six days, the prelarva grows into its larval stage. The larvae called chiggers, are about 0.17–0.21 mm in diameter light red in color, covered in hairs. The larvae congregate in groups on small clods of soil, in matted vegetation, on low bushes and plants, where they have more access to prospective hosts; the larval stage is the only parasitic stage of the mite's lifecycle. They are parasites on many animals. About 30 of the many species in this family, in their larval stage, attach to various animals and feed on skin; this causes an intensely itchy, red bump in humans. Chiggers attach to the host, pierce the skin, inject enzymes into the bite wound that digest cellular contents, suck up the digested tissue through a tube formed by hardened skin cells called a stylostome, they do not burrow into the skin or suck blood, as is assumed. Itching from a chig