Krasnotelkovye mites are a family of mites from the order Acariformes. This is a large group of small arthropods, which got its name from the bright red integument of the larvae, the color of which intensifies when saturated with blood.
The red beetle mites are characterized by a rather complex development cycle: adults and active nymphs are free-living predators that live in the soil and feed on various invertebrates, while their larvae are typical parasites that feed on the hemolymph of spiders and insects, and sometimes also on the blood of vertebrates. By the nature of feeding, the larvae of the red beetles are somewhat similar to ixodid ticks (for example, the taiga tick), and they do not have any selectivity in relation to their hosts - the larvae during periods of their activation are able to massively attack arthropods, mammals, birds, reptiles and amphibians.
Some species are able to attack a person, while feeding on blood and dissolution products of integumentary tissues. The bites of such red-haired ticks are dangerous and unpleasant, they cause a special form of skin lesions (thrombidiasis). Also, red beetles carry pathogens of a dangerous natural focal disease - tsutsugamushi fever.
On a note
Unlike ixodid ticks, krasnotelkovye, fortunately, do not tolerate tick-borne encephalitis and Lyme disease (borreliosis).However, tsutsugamushi fever is no less dangerous - if left untreated, the mortality rate reaches 40%.
We will talk further about where the red-haired ticks live, what are the features of their development, nutrition and reproduction, as well as how to protect yourself from their bites ...
Distribution and habitats
The superfamily Krasnotelkovye mites (in Latin Trombea) includes 2 families: Trombidiidae and Trombiculidae, however, representatives of the second family, which will be discussed further, are of much greater practical importance. In general, there are about 2,000 species of red beetles in the world fauna, more than 100 of them live on the territory of the former USSR.
Red beetle mites are distributed almost all over the world, they are noted on all continents except Antarctica. These parasites are also found north of the Arctic Circle, in the coniferous forests of the Kola Peninsula, but they have not been found in the tundra (this is due to the confinement of individual stages of the ontogeny of red beetles to deep layers of soil, which are strongly frozen through in the tundra).
A rich species diversity of Trombiculids is characteristic of floodplains of large rivers. Some species are found high in the mountains, at an altitude of up to 4000 m.
As for biotopic preferences, red-calf mites, like all small arthropods, are very dependent on the microclimatic parameters of a particular area. Moreover, these ticks are characterized by a rigid confinement to certain types of landscapes: there are steppe, forest and meadow species that are never found in another area.
It is interesting
Scientists have conducted research on the problem of landscape distribution of red beetle mites.It was noted that when natural conditions changed, for example, during deforestation, the fauna of the ticks under consideration also completely changed: over several years, typical forest species were replaced exclusively by steppe ones, and forest red beetles were preserved only in the beams.
The question of how exactly this change occurs is not fully understood. Red beetles are able to migrate only at the larval stage (on the body of their host), but at the same time, the small parasite cannot control in which landscape it will stop feeding and fall off. This migration is random. Adult ticks are earth mites, live in the soil, migrate only in the vertical direction, and are not capable of significant movements in the horizontal direction.
Within our country, red beetles live almost everywhere, however, the most widespread species are confined to humid habitats.
Among all other biotopes, these parasites are most often found in the following places:
- deciduous forests (most species live just in the depths of the forest);
- on glades and edges (some still go to the borders of forest plantations, since it is easier to find hosts there);
- shores of lakes overgrown with sedge;
- river valleys, with forb-grass vegetation;
- pastures and gardens;
- plowed fields (much less often).
Ticks-red beetles more often bite precisely those who decide to rest, for example, in a clearing in the forest. If a person decides to lie down on lush grass or leaf litter in places where red beetles accumulate, then there is a high probability of being bitten by their larvae.
Coloring and external structure
Since it is the larvae of the red beetles that are active parasites that pose a certain danger to humans, the description of many species is based precisely on the morphological features of the larvae.
On a note
For many species of red beetles, the imago (adult) is not even described, since it is not so easy to find an adult in the soil. In addition, taking into account the diverse structure within the same species (polymorphism), it is extremely difficult, and in some cases impossible, to compare an adult soil inhabitant and a blood-sucking larva. To compose a complete development cycle and describe each stage, scientists need to catch larvae in nature and breed red beetles in the laboratory. This is a difficult and painstaking task, which does not always end in success. That is why red beetles are considered among the least studied mites.
As noted above, the stage of the life cycle of the red tick, at which it is dangerous to humans, is the larval stage.
The larvae of some species of red beetles are very small, they are not always easy to see with the naked eye: the body length of hungry individuals is approximately 300 microns, and that of satiated individuals is 600-800 microns.
The body of the larva is not divided into segments, it looks like a bag. In hungry individuals, the integument is collected in folds, which straighten out when the tick is saturated, thereby increasing the possible volume of absorbed hemolymph or blood.
From above, the red tick is covered with bristles and hairs (trichobothria). Their number and placement on the body is strictly defined and is species-specific. The dense arrangement of bristles and numerous folds on the body of the larva look like velvet, which is why the red velvet mite is also called the “red velvet mite” (see photo below):
In general, the color of the covers can be very diverse:
- with a bright red back;
- dark red;
- in addition, the tick may be with a reddish belly and a dot on it.
The intensity of the color depends on how saturated the tick is. The color of the blood that the red beetle has sucked out is visible through the translucent integument of the body, therefore a well-fed larva is colored more intensely than its hungry relatives.
On the dorsal side, the body of the tick is covered with a shield (dense wide chitinous formation). It usually has two long bristles - sensilla. They perform the function of touch and help the small parasite to find a future victim. It is the sensilla and other trichobothria, located on different parts of the body of red-haired ticks, that perform the main sensitive function.
On a note
All bristles of the red beetle mites are located at a certain angle to the body, which makes it possible to reduce resistance during movement and increase the parasite's maneuverability. In addition, the mite is flat, and together all these factors contribute to the fact that red beetles can move very quickly along the surface of the host's body among wool and hair, while clinging tightly to individual hairs if necessary.
At the base of the scutellum there is a pair of primitive eyes - they react only to lighting, and the parasite only senses a change in the light/shadow gradient.
Larvae, unlike nymphs and adults, have not 4, but only 3 pairs of walking legs, so they can be confused with some small reddish bug.
The paws of red ticks are segmented, consist of seven sections and end in sharp claws, with the help of which the parasite clings to the wool or clothes of the future host.
On the belly is a slit-like anus (excretory pore). The genital opening is absent.
On a note
The color of red beetles does not play a primary role in the identification of these parasites. There are many red insects that look like tick larvae. Moreover, it will not be easy for an unprepared person to make such an identification - any small bug with a red booty (abdomen) may seem visually similar to a red beetle larva.
Moreover, a number of species of mites have a reddish hue, but do not belong to the Trombiculidae family. For example, if you notice a reddish mite on an apple tree that grows on a plot, or on an orchid, a lemon in a room, then most likely it is not a red-haired mite, but a spider mite. This is a completely different systematic group of parasites: they feed on plant sap, and pose absolutely no danger to humans.
Among the red beetles there is no division, for example, into citrus or apple mites, but they may well live in a garden on the ground. If you notice a small velvety red tick on a cat, then there is a high probability that this is a red beetle.
Life cycle features
The life cycle of red ticks consists of seven stages:
- egg;
- prelarva;
- larva;
- protonymph;
- deutonymph;
- tritonymph;
- adult (adult).
Experts note that in the conditions of the south-west of Russia, red-calf ticks have 1-2 generations per year, and individuals of different ages are simultaneously present in the natural environment.
The larva, deutonymph and imago are active stages, while at the stage of prelarva, proto- and tritonymph of the red beetle are at rest.
On a note
Initially, it was believed that during the resting stages, the larvae of the red tick develop complex histological processes inside, characterized by the dissolution of tissues and organs and the return of the body, as it were, to the state of the embryo. However, recent studies have made it possible to associate these changes with a special form of molting, which is a separate phase of individual development. Resting stages are now considered to start with immobilization, and the end is considered to be the beginning of active movements.
The soil is the habitat for all stages of ontogeny of red-body mites. Only the larva leaves it for the feeding period. The female and male meet in the soil, fertilization is spermatophoric (spermatophore is a sac with seminal fluid). The female grasps this pouch with her genital flaps, and fertilization occurs.
After some time, eggs are laid. Eggs are located in soil cells in groups; prelarvae are formed in them. The prelarvae hatch into larvae, which are blood-sucking external parasites, which are not characterized by selectivity in choosing a host.
The larva feeds on the tissue fluid of insects, spiders, and vertebrates and stays on them only during the feeding period. Usually, the larvae accumulate on the soil surface, lying in wait for the host, and actively attack him when approaching.
The duration of feeding on the host depends on the type of tick and can vary from 3-5 to 10-32 days.A well-fed larva leaves the host and re-enters the soil - while it may be at a considerable distance from the place where it was originally attached.
After the larva goes into the soil and successively passes through all three nymphal stages. Deutonymphs and adults are active soil predators that feed on small invertebrates and their eggs (mainly springtails).
Thus, the relationship of red beetle mites with their hosts is determined, firstly, by their use of the latter as food objects, and secondly, as a means of settling. These moments, apparently, determined the characteristics of parasitism in red beetle mites, which we will discuss a little later.
Feeding red mites
The range of hosts of red-calf ticks is unusually wide. In general, this group is not characterized by any selectivity in the choice of the future host. However, the range of possible hosts narrows depending on the state in which the tick lives.
If this is a steppe species, then, in addition to invertebrates, small mouse-like rodents can be hosts. Forest red-calf ticks usually have more choice, and trophic relationships also extend to larger mammals.
Studies of the fauna of Trombiculidae have shown that a large number of species of red beetles feed on rodents, less often saturation occurs on insectivores (hedgehogs and moles). This is followed by the parasite fauna of bats, birds and reptiles.
Humans, like primates, appear to be accidental hosts - however, many red beetles are capable of attacking humans and sucking their blood.
After hatching, the larvae are active, they crawl out of the soil and climb into the upper layers of the leaf litter or onto grassy vegetation.During this period, they are characterized by positive phototropism, that is, ticks strive for light, but at the same time avoid open areas illuminated by direct sunlight.
After some time, they slide down, forming extensive aggregations, so the bites of red beetles are often massive. In their shelters, red beetles await potential prey.
Upon contact with it, the chemoreceptors of the red tick are activated, and the parasite begins to move rapidly, actively choosing places for attachment. This process is much faster than, for example, the black wood tick.
If the host is a warm-blooded animal, red beetles choose skin areas with thin covers and a high degree of blood supply, as well as inaccessible to combing and shaking. In animals, this is mainly:
- scruff;
- auricles;
- nose;
- the area around the eyes;
- groin area;
- genitals;
- anus and perianal region.
In some species, the larvae may not look red, but yellowish:
In humans, bites are primarily exposed to open places and limbs.. The duration of feeding of the larva depends on the species and can last from several hours to two days. After saturation, the larva disappears and begins to actively migrate into the soil, where it passes into the protonymph stage. Hungry larvae do not survive the winter and mostly die.
The nature and nutritional characteristics of the red tick are determined by the structure of its oral apparatus, which is called the gnathosoma (that is, it is the entire anterior part of the body). Gnathosoma consists of 2 pairs of limbs: two-membered chelicerae and five-membered pedipalps.At the same time, chelicerae are not enclosed in any protective chambers, which is the main feature of all Acariform mites.
The head section is clearly separated from the body by a constriction, near which a specific roller is formed, which performs a number of functions. First, when the tick is attached to the body of the host, the roller plays the role of a sucker, due to which the parasite is securely attached to the victim. Secondly, such a mechanism facilitates the suction of the liquid - due to the vacuum action.
On a note
The suction of hemolymph or blood into the narrow pharynx of the parasite is carried out mainly due to the contractile movements of the esophagus. When the muscle walls of the pharynx are compressed and relaxed, negative pressure is created, and the fluid rises along the conducting paths. The skin sucker, in turn, enhances the pumping action.
Chelicerae look like thin and sharp scalpels. With the outer side of the chelicerae, the tick cuts the integument of the victim, while their inner parts create a chute along which food moves into the digestive tract of the red beetle. The palps perform a sensitive function due to the bristles located on them. They do not take part in attaching or feeding the larva, so it clings only with 6 walking legs.
When larvae of red beetles are parasitized, a special food tube is formed, called a stylostomy - because of its formation, host tissues are much more affected than when parasitized by ixodid ticks. This is one of the dangers of meeting with red-haired mites.
The stylostome is a product of the activity of the salivary glands and is a thin tube that penetrates deeply into the tissues of the host.During the feeding of the larva, the stylostome increases in length, which allows deep penetration into the integument with short mouth organs.
On a note
The developed stylostome perforates the epidermis through but never reaches the dermis. At the end of the stylostomy, an accumulation of saliva is formed and a focus of inflammation occurs. Blood elements, dead leukocytes and lysis products of the tissues of the upper layers of the skin accumulate in the focus. The longer the tick feeds, the more pronounced the inflammatory reaction becomes. The red beetle drinks not only blood - in addition to it, the main part of the nutrient substrate is precisely the lysed tissues of the victim, so the bites of the red beetle are more painful than the bites of encephalitis ticks.
In addition to external parasitism, larvae of red beetles, depending on the species, can live in the respiratory tract of mammals and birds, and also pass to subcutaneous parasitism.
Now let's talk about the types of parasitism within the group of red beetles and what a person should be afraid of first of all ...
Types of parasitism
As noted above, red beetle larvae are temporary, obligate external parasites, and if they feed on the integument of small vertebrates, they suck out blood and tissue dissolution products. However, this is only one side of the coin: studies have shown that the larvae of red beetles of different species are characterized by different types of parasitism.
Firstly, this is an external parasitism on the integument, with long-term nutrition, like in ixodid ticks. It is in this case that a full-fledged stylostomy is formed, and a strong inflammatory reaction develops with a bite. This type of parasitism is characteristic of most trombiculids.
Secondly, it is intracavitary parasitism in the respiratory tract of mammals and birds. At the same time, the mortality of red tick larvae drops significantly due to favorable microclimatic conditions inside the host organism.
Thirdly, some red beetles feeding on amphibians (frogs, toads, salamanders) are characterized by immersion under the skin of the host.
And finally, fourthly, partial immersion in the skin of the host and the formation of a kind of pockets. This type of parasitism is also widespread among the red beetles, and it is characterized by insignificant foci of inflammation, since the depth of immersion of the oral organs and the stylostomy into the integument of the host is insignificant.
Such a variety of parasitic adaptations once again indicates a high level of adaptation of red beetles, as parasites, to external factors and the ability to feed on all groups of vertebrates.
Medical significance and danger to humans
Every year in our country, cases of bites by red beetles of people are recorded. When these ticks enter the places of accumulation of these ticks, a person is often immediately subjected to a mass attack. The disease caused by the bites of these parasites is called autumn erythema or thrombidiosis.
The small size of ticks helps them to go unnoticed on the human body for a long time. They can hide in secluded places: in the hairline and in areas with a tight fit of clothing.
At the time of feeding the bloodsucker, the victim does not feel discomfort, but after a while a red spot (papule, erythema) forms at the site of the bite, which itches a lot. At night, the itching intensifies, and in some places becomes unbearable, and scratching leads to increased inflammation, and sometimes to infection in the wound.
Such erythema can cover up to 80% of the surface of the human body. After 5-8 days, redness and inflammation disappear, dark spots remain at the site of the bites. With repeated contact with red-haired mites, a more pronounced allergic reaction often occurs.
If over time the patient's condition worsens after being bitten, then another disease may develop - a natural focal disease called tsutsugamushi fever. The causative agent of this dangerous disease is rickettsia, and the natural hosts are various small rodents. It is the ability to tolerate causative agents of tsutsugamushi fever that determines the medical significance of red beetles.
If a red beetle tick has bitten an infected host (for example, a rodent), then the pathogens enter the abdomen of the parasite, and then into its saliva, and during subsequent bloodsucking, the disease is transmitted to a healthy host.
On a note
Tsutsugamushi fever is characterized by rapid clinical development: there is a severe headache, high fever. Patients complain of insomnia, they are irritable and agitated. A week later, a rash appears on the skin, the face and body swell slightly due to swelling of the tissues. The clinic of fever is very similar to the symptoms of typhus.
The disease lasts about a month, but the main complications are associated with secondary infections. If you do not see a doctor in time, then the probability of death reaches 40%.
In countries where tsutsugamushi fever is rampant (East Asia), control measures are systematically carried out in the form of treating the natural habitats of red ticks with chemicals in order to reduce their numbers.In our country, such measures have not been taken to combat soil mites.
To protect yourself from the bite of red ticks, you should follow the basic preventive rules:
- in nature, it is recommended to wear closed clothes - with tight cuffs on the arms, no holes between trousers and socks;
- it is necessary to use repellents - impregnate protective clothing and wipe the skin;
- it is not recommended to lie on the grass or the ground in places where red-haired ticks are likely to accumulate;
- after being outdoors, you need to change clothes and take a shower.
The bites of red beetles are very unpleasant and always carry the threat of infection with fever pathogens. Only following simple rules and attentive attitude to your health will protect yourself from these parasites.
Interesting video: red velvet mite
And this is what it looks like at high magnification
