The largest representative of arthropods, coconut crab! Crabs Land crabs
17/10/2016, 15:00
No doubt you can! Crabs living on the shore near the water are quite unpretentious and easy to care for. Therefore, certain types of these invertebrates can be kept as pets. They are fun to watch and don't need expensive equipment.
Land crabs cannot be kept in a fish tank, but they are fairly easy to care for and the time you spend caring for a crab is comparable to maintaining a regular water tank.
What types of land crabs can be started at home?
The most popular pets are rainbow crabs and harlequin crabs. Both of these species are quite unpretentious, have a modest size and live mainly on land. However, like all other species, they need access to water, so a crab tank needs to have both a water zone and land.
The color of the rainbow crab, as you can easily guess from the name, combines shades of purple, blue, orange and cream. The body of the harlequin crab is usually black, and the legs are orange, with purple markings on the claws. Representatives of both species are colored very brightly and look beautiful!
Housing for land crabs 
Land crabs do not need huge aquariums. These are territorial animals, which in nature usually limit their movements to a certain area. It is better to keep land crabs in pairs; if you are planning to keep a group, the aquarium must be very spacious, otherwise your pets may start fighting for territory. For two crabs, an aquarium measuring 60x30x30 cm will suffice.
In an aquarium with crabs, there should be both water and land. It is best to form a "shore" of special sand for reptiles near one of the walls of the aquarium. The depth of the water should be about 7-9 cm. The crabs will burrow in the sand, so it is very important to use sand that will hold its shape when wet and will not fall into these burrows. Over time, part of the coast is gradually washed away, therefore, in order to maintain its shape, you can create “dams” from snags or aquarium decor items.
Even if the water zone in the aquarium is relatively small and shallow, a small aquarium filter is still necessary: it will keep the water clean.
Crabs love to eat fish, so do not populate aquarium fish in the water area of \u200b\u200bthe aquarium!
Temperature and conditions of detention
The sand in the crab aquarium should always be wet; most often this happens due to constant contact with water. If you notice that the sand is dry, the air in the tank may be too dry, or the volume of water may not be large enough.
Both rainbow crabs and harlequin crabs live near fresh water. Ordinary tap water can be used, but special dechlorinators must be added to it, or allowed to stand before being poured into the aquarium.
In the wild, crabs usually live in warm climates, so you'll need a heating mat and a thermometer to keep an eye on the temperature in your tank. The mat should be placed under the part of the aquarium filled with water. The thermostat must be set to 22 degrees.
What do land crabs eat?
They are omnivores. In nature, crabs feed on plants, fish, and whatever else they can find. Special food for hermit crabs is also suitable for land crabs. You can also feed them raw fish, small cubes of frozen food intended for aquarium fish, potatoes, apples. In addition, your pet will need special calcium supplements for growth and a healthy shell.
Where to buy crabs
Land crabs are sold at some exotic pet stores. But it is better to purchase them from private breeders who can advise you on everything related to crab care.
Seeing this amazing arthropod, every faint of heart will shudder with horror and surprise - after all, there is no one in the world more interesting and, at the same time, more terrible than a coconut crab. In any case, among arthropods - after all, he is rightfully considered their largest representative.
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1. The coconut crab has many other "names" such as the thief crab or the palm thief - after all, this strange arthropod really steals its prey. Travelers of past centuries, who visited the islands spread in the West Pacific Ocean and in the Indian Ocean, talk about the fact that the coconut crab hides from prying eyes in the dense greenery of palm trees in order to suddenly grab its prey lying right under a tree or nearby From him.
2. Coconut crab (lat. Birgus latro) is actually not a crab at all, despite its striking resemblance to the arthropod relative mentioned in the name. This is a land hermit crab belonging to the species of decapods.
Strictly speaking, it is also a stretch to call a palm thief a land arthropod, since part of its life passes in the sea, and even tiny crustaceans are born in the water column. Newborn babies with a defenseless soft abdominal cavity are busily crawling along the bottom of the reservoir in search of a reliable house, which can serve as a nut shell, and an empty shell of a mollusk.
3. In "childhood" birgus latro is not too different from a hermit crab: he drags his shell along with him and spends almost all the time in the water. But having once left the larval state and left the water, he is no longer able to return there, and at some point even carry a shell-house behind him. Unlike the abdomens of hermit crabs, its abdomen is not an Achilles' heel and gradually hardens, and the tail curls under the body, protecting the body from cuts. Thanks to special lungs, he begins to breathe out of the water.
In truth, most of the legends noted this particular feature of it - the first Europeans who arrived on the islands described coconut crabs as creatures hiding in the foliage of trees with long claws that unexpectedly stretched to the very ground and captured prey, up to sheep and goats. Scientists have confirmed that birgus latro has great strength and can lift up to 30 kg of weight. However, they found out that the crab uses its abilities to drag cargo from place to place, preferring to eat dead animals, crabs and fallen fruit.
4. How do crayfish manage to exist equally comfortably both in water and on land? It turns out that wise nature provided them with two breathing instruments at once: lungs, ventilated by air on the surface of the earth, and gills, allowing them to breathe underwater. But over time, the second organ loses its functions, and palm thieves have to completely switch to a terrestrial lifestyle.
5. Those wishing to meet such a miracle would have to go to the tropics - coconut crabs are found on the islands of the Indian Ocean and on some Western Pacific islands. It is not easy to see them in daylight: palm thieves are nocturnal, and in sunny time they hide in rock crevices or in sandy burrows lined with coconut fibers - this helps to maintain the required level of humidity in the home.
6. And although the version that the crayfish is able to crack a coconut with its front claws failed miserably, its limbs, nevertheless, are sufficiently developed to quickly climb the trunk of a palm tree or bite off a person’s finger phalanx. And cancer is really not indifferent to coconuts: nutritious pulp is the main dish in its menu, to which it owes its “coconut” name.
7. Sometimes the diet of crayfish is enriched with the fruits of pandans, and according to some sources, palm thieves happen to eat their own kind. A hungry crayfish accurately finds the nearest "restaurant": an excellent sense of smell serves as an internal navigator, which brings it to the source of food, even if it is many kilometers away.
8. As for the "thieves' status" of cancer, this is due to its uncontrollable desire to pull into its mink all sorts of things from the category of the one that lies badly - edible and not very.
Coconut crab meat is not only among the delicacies, but also belongs to aphrodisiacs, so these arthropods are actively hunted. In order to prevent their complete extinction, some countries have established severe restrictions on the capture of coconut crabs.
9. The body of the coconut crab, like all decapods, is divided into the front part (cephalothorax), on which there are 10 legs, and the stomach. The front, largest pair of legs has large claws (claws), and the left claw is much larger than the right one. The next two pairs, like those of other hermits, are large, powerful with sharp ends, used by coconut crabs to travel along vertical or inclined surfaces. The fourth pair of legs is much smaller than the first three, which allows young coconut crabs to settle in shells of mollusks or coconut shells, to protect themselves. Adults use this pair for walking and climbing. The last, very small pair, which is usually hidden inside the shell, is used by females for egg care and by males for mating.
10. With the exception of the larval stage, coconut crabs cannot swim, and they will certainly drown if they stay in the water for more than an hour. For breathing, they use a special organ called gill lungs. This organ can be interpreted as a developmental stage between the gills and lungs, and is one of the most important adaptations of the coconut crab to its environment. Gill lungs contain tissues similar to those found in gills, but are suitable for absorbing oxygen from the air rather than water.
11. The coconut crab has a highly developed sense of smell, which it uses to find food. Like most water crabs, they have specialized organs located on their antennae that determine the concentration and direction of scent.
12. During the day, these arthropods sit in burrows or rock crevices, which are lined with coconut fibers or foliage to increase the humidity in the dwelling. While resting in its burrow, the coconut crab closes the entrance with one claw to maintain a humid microclimate in the burrow, which is necessary for its respiratory organs.
13. As the name suggests, this crab feeds on coconuts, and is actually able to climb a coconut tree, up to 6 meters high, where it plucks coconuts with powerful claws if they are not yet available on the ground. If a fallen coconut does not split when it falls, the crab will gut it for a week or even two until it gets to the juicy pulp of the nut. If this dreary job bothers the crab, he lifts the coconut up the tree and throws it down in order to make his work easier. Descending back to the ground, they sometimes fall, but without damage to health they can endure a fall from a height of 4.5 meters. The coconut crab will not refuse other fruits, newborn turtles and carrion. They have also been seen catching and eating Polynesian rats.
14. Another name for it is the palm thief, he received for his love for everything shiny. If a spoon, fork, or other shiny object gets in the way of a crab, you can be sure that he will certainly try to drag it into his mink.
15. From the beginning of June to the end of August, the palm thieves begin the breeding season. The courtship process lasts long and tedious, but the mating itself takes place quite quickly. The female carries fertilized eggs for several months on the underside of the abdomen. When the eggs are ready to hatch, the female descends to the seashore at high tide and releases the larvae into the water. During the next three to four weeks, the larvae floating in the water go through several stages of development. After 25 - 30 days, already small crabs sink to the bottom, settle in the shells of gastropod mollusks, and prepare to migrate to the ground. At this time, babies sometimes visit land, and gradually losing the ability to breathe underwater, they finally move to the main habitat. Coconut crabs reach sexual maturity about five years after hatching, but do not reach their maximum size until they are 40 years old.
16. Palm thieves live in the tropics, on the islands of the Indian and Western Pacific Oceans. Christmas Island in the Indian Ocean has the highest population density of coconut crabs in the world.
17. Swedish and Australian scientists have confirmed the veracity of all the stories about coconut crabs. So, the inhabitants of the Pacific islands claimed that they could smell, for example, meat or ripe fruits a few kilometers away. And indeed, the special baits planted by the researchers immediately attracted the attention of thieving crabs, who nevertheless disdained the usual pieces of bread that ordinary crabs are greedy for.
18. The janitor function is, of course, not bad and useful, however, since the birgus latro creature is predominantly nocturnal and not very friendly, stumbling upon it, the locals are not particularly enthusiastic. The decrease in its numbers forced the local authorities to set a limit on the capture of birgus latro. In Papua New Guinea, it is forbidden to include it in restaurant menus, on the island of Saipan - to catch crabs with a shell of less than 3.5 cm, and also from June to September, during the breeding season.
19. On the inner surface of the walls of the gill cavities, this terrestrial descendant of hermit crabs develop grape-like skin folds, in which numerous blood vessels branch. These are real lungs, allowing the use of oxygen from the air filling the gill cavities. The lungs are ventilated due to the movements of scaphognathite, as well as due to the ability of animals to raise and lower the carapace from time to time, for which special muscles serve.
It is remarkable that the gills are also preserved, although they are relatively small in size. The removal of the gills did not harm the breath in the least; on the other hand, the crayfish has completely lost the ability to breathe in water. Submerged in water, the palm thief died after 4 hours. Residual gills, apparently, do not function. The palm thief digs shallow holes in the soil, which he lines with coconut fibers. Charles Darwin relates that the natives on some islands select these fibers from the burrows of the palm thief, which they need in their simple economy. Sometimes a palm thief is content with natural shelters - crevices in rocks, cavities in drained coral reefs, but even in such cases, he uses plant material to line them, which retains high humidity in housing.
The land hermit crab is a land crab that can drown if it stays in the water for a long time. It lives in the Caribbean Sea, it is also common in Venezuela, the Bahamas, Belize, India, Florida, the Virgin Islands. These crabs are also called tree crabs, tropical land hermit crabs, and Caribbean hermit crabs.
Description of the land hermit crab
There are 7 varieties of tropical land hermit crabs. These crabs reach a length of about 3 centimeters, the weight of an adult reaches 110 grams.
The body shape is cylindrical, elongated. The body is covered with small hairs. The front part of the body is protected by a hard shell, and the abdominal part is much softer.
Land hermit crabs have 5 pairs of legs. The first pair are pincers. With the help of the right claw, the crab eats, and the left one is used for protection, for example, it can close the entrance to the hole in time of danger. Most crabs have purple claws, but they can also be lemon, brown, or red. The second and third pair of crab legs are for walking. The last two pairs of legs are very small and sometimes do not protrude from the shell.
Caribbean hermit crabs breathe with gills. There are 2 pairs of retractable antennae: long antennae are used for touch, and short ones perform the function of smell. Land hermit crabs have good eyesight.
When the crab is outside the shell, its sex can be determined: the male has hairs on the last pair of legs, and there are no appendages on the abdominal cavity.
Lifestyle of land hermit crabs
Tree crabs are social animals that live in large groups. They lead a nocturnal lifestyle, their peak activity is observed at 20 o'clock. Land hermit crabs do not like high temperatures and the sun, so during the day they hide in small holes, under stones, logs, leaves, and the like.
Land hermit crabs live on the sandy shores of the Caribbean islands, at a distance of 1.8-3.5 kilometers from the water. They are found among coastal plants. They avoid swamps and places with dense vegetation. Hermit crabs prefer low salinity water.
If a tropical land crab is left in the water for a long time, it will drown. Adults molt every 12-18 months, while juveniles molt several times a year. After molting, the crab chooses a new, larger shell.
At temperatures below 20 degrees, the activity of land hermit crabs decreases, and at temperatures below 18 degrees, they hibernate. These crabs can make various sounds: chirping, crackling, croaking.
Tropical land hermit crabs feed at night. They are omnivorous scavengers. Also, their diet includes cactus fruits and even fresh litter of horses and cows. In captivity, they can live up to 11 years.
Reproduction of land hermit crabs
The breeding season for tree crabs is August-October. To mate, males and females have to leave their shells. Young females lay 800-1200 eggs, and adult females - 40-50000 eggs. The color of newly laid eggs is red-brown, within a month they turn blue or gray.
3 weeks after mating, the female goes to shallow water, her eggs are on the 5th leg, she collects them and transfers them to wet stones. The eggs are washed away by the waves into the water.
In the larvae of land hermit crabs, several stages of development are observed: zoe, then glaucotoe, after the young crab. During metamorphosis, the larva settles to the bottom, and then crawls out onto land.
Zoe is thin and long, its size reaches 3 millimeters. She has 2 large eyes. At this stage, the larva feeds on plankton. Zoe makes 3-4 molts, during which it grows.
After 4-5 molts, the larva passes into the stage of glaucotoe. At this stage, it develops very small antennae, eyes are located on stalks, and the first paws are transformed into claws. Glaucotoe looks like an adult crab. This stage lasts about a month, after which the larva grows to 5 millimeters.
Before the last stage, young crabs begin to look for a shell. If a crab comes out of the sea without a shell, it usually dies.
On land, young crabs are active mainly at night, and during the day they hide in various cracks and crevices.
These crabs are kept in horizontal type terrariums. The soil is partially flooded with water, but the water level must be very low, as land hermit crabs drown easily.
- Class: Crustacea = Crustaceans, crayfish
- Subclass: Malacostraca = Higher crayfish
- Order Decapoda = Decapod crustaceans (crayfish, crabs...)
- Suborder: Pleocyemata Burkenroad, 1963 = Crabs
- Infraorder: Brachyura Latreille, 1802 = Crabs, short-tailed crayfish
Land (land) crabs
Crabs are marine life, and it is hard to imagine that they can live on land, and even more so in trees or in arid regions. Therefore, land-based land crabs are an unusual zoological phenomenon.
The conquest of land by crabs was gradual. Crabs had 10 times less time to conquer land than insects, but their success in adapting to terrestrial existence is very significant. The initial stage of this process is the development of ghost crabs and soldier crabs on tropical beaches. These crabs live in burrows in coastal areas regularly flooded by ocean tides.
Mangrove crabs living on the roots and branches of mangrove trees in tropical rainforests have taken the next step towards land development. All these crabs migrate to the sea for breeding, and after breeding is completed, they again leave for many kilometers from the coast.
Another way for crabs to explore the continents is their adaptation to life in fresh water (see). Along the rivers and streams, these crabs penetrated far into the depths of the continents, climbed the mountains, mastering even the Himalayas. Some crabs, such as the bromeliad crab Metopaulias depressus, have adapted to live in the axils of large leaves of land plants, where rainwater accumulates.
Tropical earth crabs spend their whole lives on land, living in bare desert areas where huge cacti proudly rise above the sands. These crabs can be found at a distance of several kilometers from the sea, where in search of food they roam the clearings overgrown with thorny bushes and barren savannahs. These crabs feed on leaves and other greens.
In the deserts of Australia, thousands of kilometers from the sea, a crab lives, which uses night dew and carries juveniles in a tightly closed “pocket” on its abdomen. The main problem for land crabs is the fight against desiccation. They solve this problem in several ways. Firstly, dense calcareous covers of the body prevent drying out, and secondly, crabs go hunting only at night or after heavy tropical rains, hiding in underground burrows during dry times. In addition, real gills in earth crabs are transformed into a "lung", the respiratory surface of which is moistened due to the presence of tufts of bristles that suck water from the sand. Crab burrows, dug in soft ground, form complex labyrinths several meters long. Often one of the exits leads to a reservoir, due to which high humidity is maintained in the crab's cave.
An extremely unusual respiratory organ was formed in land crabs skopimera and dotilla. These crabs live at the very edge of the water, gathering food on the bare seabed at low tide, and hiding in deep burrows where air is stored at high tide. They breathe with their feet. The hips of the walking legs of these crabs are greatly expanded, and in their middle there is a “window” covered with a thin membrane. In scopimera, windows, the width of the entire segment, are located even on the front claws. In dotilla, they are smaller, but they are also located on the sides of the shell. Previously, it was assumed that these windows serve as organs of hearing, but it turned out that these are real respiratory organs. Crabs with windows smeared with paint begin to suffocate and try with all their might to peel off the paint. Directly under the membrane, inside the segment, there is a complex system of tubules filled with blood. The venous blood passing through them comes into contact with the "gas window" and is enriched with oxygen. The total gas exchange surface of these crabs is large - up to square millimeters, that is, more than that of terrestrial crabs that breathe with their lungs.
Ghost crabs are nocturnal. During the day, they escape from overheating and drying out in deep burrows (up to 1.8 meters deep in large individuals) with a closing entrance. They feed on living crustaceans, mollusks, plant foods (even seeds), and decaying remains. On land, ghost crabs move in sharp dashes at speeds up to 1.8 meters per second on sand and up to 2.3 meters per second on solid ground. Crabs do not avoid humans and even concentrate in places where they find the remains of his food (near baths, beach cafes, etc.).
The most imposing of them (32 cm long), armed with powerful claws, and the most famous are crayfish (or crabs - as they are called) palm thieves, or robber crayfish. They are distributed throughout the islands of the Indian and western Pacific Oceans.
Palm crayfish are a kind of amphibian: their larvae live in the sea, while adults completely parted with it as purely land animals. They can even drown in the sea! If an adult palm thief is lowered into water, then he will last in it for a maximum of 5 hours, and then he will die.
But on land, they feel great. They run quickly sideways, like crabs. See? Hear? Feel? Feel? In a word, by the vibrations of the earth, they learn in time about the approach of a person or ... a pig
their worst enemy is now on many islands. And if there is any danger - they immediately rush to their shelters (or the nearest ones that get in the way) and hide in holes, between stones, in crevices of the earth or the surface of the reef.
For life on land, they are given by nature a special respiratory device. It is called lungs, but it looks more like a labyrinth organ of fish - on the inner wall of the gill cavity of the crayfish, "groin-shaped folds of skin were formed, in which numerous blood vessels branch." The blood in these folds receives oxygen directly from the air and releases carbon dioxide. So everything flows like in the lungs. Only as if turned inside out.
And then one day, at a time determined by nature, the female palm thieves nevertheless go to the ocean. Their abdominal legs are burdened with caviar. Having plunged a little into the water or standing on a stone, which is constantly washed by gentle waves, they vigorously shake their belly: they dump the eggs they have generated into the sea. On land, they hatched them for three to four weeks.
From the eggs, larvae soon emerge, not at all like robber crayfish. Once in the sea after four to six months, the larva sinks to the bottom. Here she takes on the appearance of the animal with which we have just parted - her alleged ancestor of the hermit crab. The same as his, easily injured, soft, slightly spiral abdomen, and just like him, she hides it in empty snail shells. Still lives in the sea. When he grows up, he takes the first step into a different, previously completely alien element, gets out on the shore. On land, it lives for several months in the shell of land mollusks. Sheds and leaves the shell forever. Her belly is shortened, folded under the chest and is no longer as soft as before: its skin has become denser from the fact that it was saturated with calcium salts. In this way, the larva turns from a hermit crab into a palm thief.
The palm thief is omnivorous (and eats fruits, soil, and other crabs too), but, according to some researchers, it has a special propensity for coconuts. Incredible stories are told about the palm thief!
The palm thief deftly climbs twenty-meter-high coconut palms, but it is enough to put a bandage of grass on the trunk of a palm tree at a height of several meters, as a poison thief stumbles and flies down, where local residents pick him up, smashed or at least stunned. These crabs feed on oily coconuts so much that they themselves render up to 1.5 kg of excellent oil. When catching "palm thieves" one must be careful: with their claws, they can easily cut off a finger. Their burrows are found right there at the foot of palm trees.
Often this crayfish was found on a palm tree, at a height of 20 m, where it cut nuts with powerful claws to then eat them on the ground. First, he removes the peel, and then opens the nut with his large claw.
The second land fellow of the marine hermit crab - cenobit crayfish lives in general in the same place as the palm thief. Even for adults, he does not part with the shell in which he hides his soft belly. So it drags it on itself over the unevenness of the soil, which is much harder work than that of the sea hermit crab: after all, in the water, the earth's gravity does not affect its inhabitants so much as it does on the inhabitants of the land.
Cenobita is essentially a land hermit crab (but without sea anemones on the shell). A completely new respiratory organ arose only among terrestrial inhabitants of the genus cenobite ... Its abdomen, covered with highly wrinkled skin, is permeated with a highly developed system of blood lacunae, which serve for direct gas exchange. The gill cavity plays a subordinate role. It is possible to remove the reduced gills... and even the wall of the carapace, and this will not cause significant harm to the animal's breathing. In water, species of the genus cenobita can live only a few hours.
Land crabs are wonderful round-faced creatures that live in burrows in the depths of the Bahamas sharply bob. Their place is not on the shore, but in arid spaces, where huge cacti proudly rise above the sands. They can be found in places miles away from the coast...where they roam thorny scrub clearings and barren savannahs in search of food (tree branches and fresh greenery). In the shade of bushes and under the roots of trees, they dig deep holes, long winding caves: scraping clay with claws, roll it into lumps and put these lumps one by one at the entrance to the hole. On warm tropical nights, they go to feed and return to their lairs with juicy green branches. The rainy season ends, the tropical sun bakes hotter, the lakes dry up, the earth cracks, the plants wither, only the cacti remain fresh and green. In this difficult time for crabs, they hide in the depths of holes, where at least some freshness has been preserved. They do not go to feed, even at night. They are starving. They sit in their drowsy, suspended animation-like state. They are waiting for the rain. But then thunder struck - water gushing in continuous streams, spilling over the earth like a flood. From all sides, crabs come to the surface, straying into huge shoals, and set off along the rain-washed gravel. And the path is the same for everyone: neither the lakes again filled with water will attract them, no stones or thickets will stop them - they rush to the ocean, to the sand of the surf, which is now captivating for them. They go to sea to breed.
Ghost crabs, scurrying in silent shadows across the sand beyond the coastal strip, bear the scientific name "ocypods". They are really elusive, like ghosts: not every person will run after them. They are so lightning fast in their movements that sometimes even small birds are caught!
Ocipods are not real land crabs, but amphibians: they live on the border of land and sea and cannot do without water for a long time.
These are common inhabitants of the coasts of all warm seas and often settle in large companies. A little above the tide line, they dig vertically downwards in the ground, leaving holes that reach the groundwater. In the morning and evening, or at low tide, quickly seeding with their legs, they scurry along the shore in search of dead fish, crustaceans, fruits, rummage in the silt, extracting from it every trifle edible to their taste. At the slightest danger, they rush to their burrows and hide in them. They are so well oriented that when they tried to carry them away from the hole for 200 meters, they still found it.
The same burrows, reaching deep to groundwater, are dug in the tidal zone or among mango thickets and close relatives of ocypods - the so-called alluring crabs. They live in tighter necks than ocinodes: on one square meter of land, it happens that up to 50 of these crabs settle (however, they are small in stature: the width of the carapace is up to 3.5 cm, but more often even less).
At high tide they sit in their burrows. The tide will begin to ebb - they go to look for food: they rummage in the silt, fishing out everything suitable for food from it.
From time to time, this or that male interrupts the meal in order to perform a seemingly strange ritual, because of which these crabs got their unusual name. In males, one claw (usually the right one) is much larger than the other. With it, he makes alluring movements. Here the crab stood up in its original position: it lifted a huge claw from the ground and set it right in front of it. Suddenly he abruptly took her to the side, immediately lifted her up and again lowered her down in front of him, to the starting position. All this claw manipulation lasts about 2 seconds. And the more excited the male, the more often he repeats his alluring movements.
At night or in dense thickets, when there is practically no visibility, the male does not wave his claws, but rather loudly knocks on the ground with it. The female then learns about his call by slight vibrations of the earth and hurries to him.
Attracting a female is not the only purpose of the crab's alluring movements. He does the same in front of another male - a contender for his apartment or for a female. And if the rival does not retreat, a fight may break out between the males.vv