Two-tailed is the creature that most closely resembles real insects. They are six-legged and have the international name Diplura. The German naturalist Karl Berner described them in 1904
Origin and Description
This arthropod is included in the class of cryptomaxillaries, uniting the most primitive creatures that lead a very secretive lifestyle, and are closely related to the soil, in addition to the two-tailed, this class includes springtails, springtails. These three species are united by the fact that their oral apparatus is retracted into the head capsule, hence their name.
Previously, this subclass belonged to insects, but now it has been allocated a separate class. Individuals of the two-tailed order are closest to insects. They are larger than other representatives of the cryptomaxillaries: protur and springtail. How the development of six-legged historically took place is poorly understood. But one species of two-eyes is known, dating from the Carboniferous period – this is Testajapyx. Individuals had compound eyes, as well as a mouth organ similar to that of real insects, in this they are closer to them than to modern representatives of Diplura.
Three large groups are distinguished in this species:
The most common are:
- Campodean family;
- Iapix family.
Appearance and features
Most representatives of bivostok are small in size, only a few millimeters (0.08-0.2 mm), but some of them reach several centimeters (2-5 cm) in length. They do not have eyes or wings. The elongated fusiform body is divided into a head, a thorax with three segments, and an abdomen with ten segments. The first seven segments of the abdomen have outgrowths called styli. The animal leans on these multiform outgrowths when running.
An interesting fact: The terminal segment is equipped with rudimentary modified legs called cerci, they resemble antennae or double tails. It is because of them that these creatures got their name, two-tails or forktails.
In representatives of the forktails – yapiks, these outgrowths are short, rigid, similar to a claw. Such cerci are used to catch and hold their prey. In the family Campodea, the cerci are elongated and consist of segments. They play the role of sensitive organs, function as antennas. In the well-known species Projapygoidea, the cerci are thick, shortened, but segmented.
Such individuals also have some unique adaptations – these are abdominal rotating glands at the ends of their shortened cone-shaped caudal processes. Rotating glands produce the filaments used to immobilize prey, as if pincers or jaws are not enough.
The three thoracic segments of the six-legged are prominent, each bearing a pair of slender, long legs. The covers of the cryptomaxillary are tender, soft and thin so that breathing is carried out through them. In addition, bivostok have a tracheal respiratory system and eleven pairs of spiracles. Forktail antennae also consist of a large number of segments: from 13 to 70 pieces, and each segment has its own musculature. For example, open jaws do not have such muscles.
Where does the two-tail live?
Forktails are very secretive, difficult to spot, and their small size, translucency and mimic coloring contribute to this lifestyle. They live in anthills, termite mounds, caves. They live in rotten wood, upper layers of soil, leaf litter, moss, tree bark. You will not meet them on the surface, as they love moisture.
In some countries of the world, certain species live in root crops. It has also been reported that there are representatives that are pests of crops such as sugar cane, peanuts and melons. The most common are individuals from the Campodea family. They are extremely mobile. In appearance, these are gentle and slender creatures, with long antennae and even longer cerci. Six-legged live in soil or rotting garbage, where there is a lot of food for them: small insects and mites, vegetation remains.
What is especially important for providing conditions suitable for the life of these creatures is high humidity. At dry temperatures, the individuals themselves, their larvae and eggs dry out. But there are some subspecies that are more adapted to dry climates, which expands the known geographic range of the bivostok.
Living in the Crimea, on the southern shores, Japix ghilarovi is 1 cm long. In Turkmenistan, the largest representative of this family, Japix dux, is found, it reaches five centimeters in length. In the rainforests of Africa, two-tails live, having features of both Iapix and Campodea – Projapygoidea.
What does the two-tail eat?
Digestive system in of these creatures is very peculiar due to the structure of the oral apparatus. It is of a gnawing type and the mouthparts point forward despite being hidden in the head. The intestinal canal of bivostok looks like a simple tube.
The upper jaws are in the form of a serrated sickle, they are of a grasping type. From the outside, only the very tips are visible, and the rest is hidden in recesses that have a complex shape and are called jaw pockets. The lower lip and pockets form a single unit. The upper jaws or mandibles – mandibles, as well as the lower ones – maxillas are hidden in the recesses. Yapixes, and many other species of forktails, are predators.
They feed on:
- tiny arthropod insects;
- their relatives the Campodeans;
Those forktails, in which the cerci are arranged in the form of claws, seizing the prey, arch their back so that the victim is in front of the head, then eat them. Some of the representatives are omnivorous and feed on detritus, that is, the organic remains of invertebrates and vertebrates, particles of their secretions and undecomposed pieces of plants. Their diet also includes mushroom mycelium.
Character and Lifestyle Features
Forktails are difficult to follow, they are small and very restless. Almost all of the shots that have captured the creature are taken from above, but not from the side. It used to be that the outgrowths on the abdomen were just rudimentary organs.
After long-term observations and obtaining enlarged photos, it became clear that the six-legged use their protruding stylus on the abdomen as limbs. When moving on a horizontal surface, they hang freely. When overcoming vertical obstacles, forktails actively use them as legs. Movable campodeans have sensitive cerci at the end of the abdomen, which are used for the same purposes as the antennae. They move very quickly in search of prey, feeling the way with their antennae in the cracks of the earth, sensing the slightest obstacles.
Interesting fact: Campodeans can run head-first or vice versa equally well. Legs and outgrowths on the abdomen are well adapted for movement back and forth. And the cerci on the tail of the abdomen successfully replace the antennae-antennae.
Campodea sensitively reacts to the most insignificant air tremors that arise from a moving victim or enemy. If this creature stumbles upon an obstacle or senses danger, it quickly takes off running.
Interesting fact: Two-tails can reach speeds of up to 54 mm/s, which is twenty-seven body lengths per second. For comparison, a cheetah runs at about 110 km/h. In order for a cheetah to move at the same relative speed as a forktail, it must develop it up to 186 km/h.
Social structure and reproduction
These primitive beings are divided into two sexes. Males and females may differ in size. Fertilization in bivoctates, like in other cryptomaxillaries, has an external-internal character. Males lay spromatophores – capsules containing spermatozoa. These capsules are attached to the ground with a short stem. In a week, one individual can lay up to two hundred such spermatophores. It is believed that their viability lasts about two days.
The female picks up spermatophores with her genital opening, and then lays fertilized eggs in cracks or depressions in the soil. Individuals emerge from the egg, completely similar to adults, they have fewer outgrowths on the abdomen and no genitals. Diplurans spend their first few days immobile and only after the first molt do they begin to move and forage.
From the larva to the adult specimen, development occurs in a direct way through the stages of molting, which can be about 40 times in a lifetime, they live for about a year. There is evidence that some species can live for three years.
Interesting fact: It is known that Campodeans leave their eggs, while Iapixes remain close to the clutches, protecting eggs and larvae from enemies.
Two East Natural Enemies
The little-studied of these creatures, their secretive nature life does not allow to fully and accurately determine the entire circle of their enemies. But here you can include predatory mites, representatives of false scorpions, rove beetles, ground beetles, empid flies, ants. Rarely, but they can become prey for spiders, frogs, snails.
Changes in the macroflora also affect the population. Direct cultivation (such as ploughing) has an immediate harmful effect but does little damage. Fertilizers increase the number of individuals in the soil, and herbicides do not act on them. Some insecticides are lethal, and the increase in numbers of bivostok after insecticide application is likely due to the lethal effects of the chemicals on their enemies.
Interesting fact: Some of the bivostok can discard their tail cerci in case of danger. They are the only arthropods that are able to regenerate a lost organ after a series of molts. Not only cerci, but also antennae and legs are subject to restoration.
Population and species status
Groups of two-tails that live in the ground are large in number and are an indispensable part of the soil biocenosis. They are distributed throughout the world, from the tropics to the temperate zones. These creatures are more common in countries with a hot and humid climate, but there are up to 800 species in total, of which:
- in North America – 70 species;
- in Russia and post-Soviet countries — 20 kinds;
- in the UK, 12 species;
- in Australia — 28 types.
Yapiks are found in the Crimea, in the Caucasus, in the countries of Central Asia, in Moldova and Ukraine, as well as in hotter countries. These creatures do not have any conservation status, although some of them, such as the large yapix, are protected in some countries. In the United States, in the state of West Virginia, the two-tailed Plusiocampa fieldingi from the Campodea family is included in the list of rare species. In New Zealand, the Department of Agriculture lists the forktail Octostigma herbivora, a member of the Projapygidae family, as a pest.
Fun fact: Springtails are often confused with earwigs. Those also have claw-shaped formations at the end of an elongated body. Earwigs belong to the class of insects. On closer examination, they have eyes, very small wings and hard elytra, they have a dense cover, and the abdomen consists of 7 sections. The size of insects is larger than the forktails that are found in our country, and earwigs also move quietly on the surface of the earth.
You should not confuse the cryptomaxillaries with centipedes, in which all limbs are approximately the same size, and the two-tails have three pairs long legs, and the rest are small scallops on the abdomen. The two-tailed, for the most part, is a harmless and even useful creature that helps composting, processing the remains of organic materials. A person may not notice their presence, as they exist in the soil and are so small that they are difficult to notice.