According to scientists, Australia is currently home to about 200,000 species of animals. Most of the creatures living on this continent cannot be found on other continents, that is, they are unique. It just so happens that people associate Australia with poisonous snakes, spiders and other scary creatures. And this is very fair, because the Internet is full of stories about how Australians discovered huge snakes right in their toilet and deadly spiders in the living room. In fact, most Australian snakes and spiders are harmless to humans, but how do we know? After all, not everyone knows how to recognize animal species by their appearance alone. To help people quickly identify the venomous properties of snakes and spiders, CSIRO has developed the Critterpedia app. Users can take a photo of the animal and the service will quickly determine its type and degree of danger to humans.
The Sydney leukoweb spider (Atrax robustus) is one of the most dangerous inhabitants of Australia.
External structure
External structure of a spider
Spiders are heterosexual, and in most species the males are smaller than the females. This is due to the fact that when creating offspring of a female, it is then easier to eat the partner and produce more cubs. At the back are the warts, from which the warts stand out.
Body
The body consists of a cephalothorax covered with chitin, a hard exoskeleton. During its life, it can be updated up to 10 times, and the old one is reset only after a new one is formed under it.
Limbs
Spiders have four pairs of legs covered with small hairs.
There are also two pedipalps on the body, which are responsible for the sense of smell. Next to the jaws there are also chelicerae, with the help of which the predator injects poison into the prey. Interesting fact : thanks to the hairs on its limbs, the spider senses the direction of the wind and orients itself in space.
Color
The main components that determine the spider's color are bilin and guanine. They add brown and white to the body respectively. Also, other shades appear due to the light reflection characteristics of the hairs on the body.
Determination of gender
One of the most important aspects associated with the successful breeding of tarantulas in captivity is the ability to determine the sex of the spider as early as possible in order to slow down or maximize its growth and onset of puberty.
Recent research by scientists (Rick West, Mark R. Hart), based on the work of B.J. Marples, "The Spinnerets and Epiandrous Glands of Spiders", 1967, provided the only truly possible way to accurately determine the sex of a tarantula from a living specimen. As already mentioned when considering the arachnoid apparatus of tarantula spiders, only males have special arachnoid glands, the appendages of which barely noticeably open with openings in the epiginum , anterior to the epigastric groove . These holes are arranged in 2-4 rows, having a semicircular or triangular shape. The area where they are located can be determined by denser and shorter dark hairs arranged in the form of an “arch” (see figure).
These appendages, similar to the main spinneret (web appendages) of a spider, are called epiandrous fusillae (epiandral glands) and are used by males in spinning sperm - webs . Therefore, if they are found in a tarantula, then this specimen is a male; if they are not present, it is a female. However, mastering this method requires some practice, you need to have a “trained eye”, which comes with experience. It can be especially difficult to determine the sex of species that have a light color on the underside of the abdomen and the special hairs themselves - Aphonopelma seemanni, Nhandu coloratovillosus, Megaphobema robustum. It also requires precision and careful handling of spiders. But this method is unique and effective, since it is based on a scientific approach and is the only one that allows you to reliably determine the sex of a living tarantula spider.
This method allows you to determine the sex even of spiders of early instars, however, this requires good additional lighting and a binocular or microscope.
The next, also absolutely reliable and accurate way to determine sex, is to study the exuvium (old exoskeleton) of the tarantula remaining after its molt.
To do this, you need to straighten the exuvium as shown in the figures and pay attention to the area between the first pair of white spots, located at the base of the abdomen. These spots determine the location of the tarantula's lungs - the first and second pairs, respectively. The tarantula spider's genitals are located in this area, and the female's exuvium has a mark from the spermatheca (spermatheca) , which is well defined in adult females. In the exuvium of males this place has a smooth edge.
To determine the sex of small individuals, good lighting and strong magnification are necessary, which is quite difficult due to the usually weak expression of the spermatheca “pocket” in juvenile females. The shape of the spermatheca pouch varies among species.
It is also necessary to take into account that many species, in a short time immediately after molting, manage to “chew” the discarded exuvium, thereby rendering it in a state unsuitable for sex determination. Therefore, to avoid this, it is necessary to remove the exuvium immediately after the tarantula has moulted, without in any way disturbing the spider itself.
Recently, another “comprehensive” method for determining the sex of living spiders has also become widespread, which makes it possible with a high degree of probability to determine whether a specimen is male or female, respectively, by the shape of the epigastric groove, the distance between the anterior pair of lungs and the angle of inclination of the anterior lungs.
Internal structure
Internal structure of a spider
Spiders have a complex internal structure, and several systems continuously function in their bodies.
central nervous system
Consists of the nervous system and brain. The latter is a collection of ganglia. It is responsible for the functioning of the eyes and perception of the environment. The spider's brain is developed enough to analyze and act not only on instincts, but also on existing experience.
Circulatory system
This system is not closed. The heart is located inside the abdominal cavity; the role of its valves is performed by stomata, which close during pulsations. The circulatory system runs through the entire body and into the limbs.
Digestive system
In the process of eating food, the spider's digestive system begins to work. When a predator pulls fluid from its prey, it ends up in the foregut. In it, part of the liquid is absorbed into the walls, and the rest is transported to the stomach. Spiders also have a liver, which is responsible for breaking down food particles.
Nutrition
As mentioned above, the main dish of spiders is insects. But the eating process itself is of greater interest, because digestion occurs outside the intestines. The meal can take from 1 to 3 hours.
By piercing the caught prey with chelicerae, the spider injects digestive juice into it in portions, which is produced by the labial glands and liver. It dissolves all soft tissue, leaving hair, bones and chitinous cover. These same chelicerae cause damage, as a result of which the ready-to-use “cocktail” comes out. Like the movements of a cat's tongue, the spider eats it with the help of the muscular rostrum, and then repeats the actions, turning the victim on the other side.
Reproduction
Female with spiderlings
The mating season for spiders begins in autumn and lasts until spring. At this time, the male goes in search of the female. Having found a suitable candidate, he begins to perform a special dance that attracts attention. If the female reciprocates, then they retire. After this, the male moves away, and the female begins to wait for offspring. After two and a half months, she lays eggs, and after another month, the young hatch from them.
How do they breathe
Respiratory system of spiders
Depending on the species, spiders may have the following variations of the respiratory system:
- one pair of lungs;
- two pairs of lungs;
- a pair of lungs and a pair of tracheas;
- pairs of sieve and tubular tracheas;
- pair of sieve tracheas.
Getting inside the spider through special holes, oxygen is transported through the hemolymph to the respiratory organs with the help of hemocyanin. The lung sacs are located in the front of the abdomen. They saturate the body with oxygen through the circulatory system. Also behind the pulmonary sacs are bundles of tracheae, which are small tubes. They exit through a single breathing hole. During exhalation, the spider releases the resulting carbon dioxide into space.
How do they winter
Some spiders can lead an active lifestyle in winter.
Spiders are able to hibernate in different ways. Some survive frosts in the foliage and bark of trees. Spiders also try to escape the cold by settling in different buildings. In the cold, the predator produces a special chemical that acts as antifreeze. If a female lays eggs before the onset of cold weather, she tries to hide them in a secluded place where the temperature will still remain above zero in the winter.
Interesting fact : in the cold, spiders fall into a state similar to suspended animation. Because of this, processes in the body slow down and they age more slowly.
How many eyes does a spider have?
Spider Eyes
The number of spider eyes varies from 2 to 12 depending on the species, but in most cases there are 8. They are located in such a way that the creature's viewing radius is 360 degrees. Spiders see what is happening around them at about 30 cm. The main task of the visual organs is to notice in time the approach of prey or danger. Also, some types of spiders can distinguish between colors.
In the center of the head is the main pair of eyes, which are larger than the others. With their help, the spider focuses on objects. The lateral eyes are motionless and are needed for additional visibility.
Danger to humans
As mentioned above, the substance injected by spiders causes the greatest harm to the body. Their poison glands produce 2 types of poison:
- neurotoxic - affects the nervous system, muscles, heart and internal organs;
- necrotic - causes cell death.
In order to cause serious harm to the body, an impressive portion of poison and a weakened immune system are required. With this combination of circumstances, paralysis may occur, the heart rate may become erratic and the limbs may go numb.
Are spiders insects or not? Difference between spiders and insects
Spider and Beetle
Spiders are not insects. Despite the fact that they also belong to the type of arthropods, they have a number of differences:
- Spiders have four pairs of limbs, and insects have three;
- spiders have chelicerae with which they inject venom into their prey;
- the head of insects is clearly defined, and in spiders it is combined with the body;
- Insects have only one pair of eyes;
- all types of spiders (with rare exceptions) lead a predatory lifestyle and do not eat plants;
- spiders breathe using pulmonary sacs, and insects use only tracheas;
- Insects have antennae on their heads.
Also, one of the main differences between spiders and insects is the ability to weave webs.
Primary sexual characteristics
During puberty, primary sexual characteristics become visible in animals. To find them, you need to examine the abdomen and cephalothorax from the back. This method of determining the sex of a tarantula is used only for arthropods that are not distinguished by their aggressive nature and highly toxic poison.
- Use your fingers to press on the dorsal shield, pressing the individual to the ground.
- Take the spider by the sides of the cephalothorax. The animal presses its limbs to its body.
- The tarantula is turned over with its paws up and examined.
- Find the epigastric groove. It is located on the upper part of the abdomen, closer to the cephalothorax.
- Inspect the hair above the furrow.
- The male tarantula has hairs of varying lengths. The darker bristles form an arched pattern. In this area, spiders have male reproductive glands. Before mating, seminal fluid is released from them.
- Females have hairs of the same size and shade. No drawings are found.
Harmless species of spiders
If the spider's venom is mildly toxic and causes almost no harm to humans, such species are considered harmless and non-poisonous. There are a large number of species in the world, and the main ones are listed below.
Hunter bordered
Border hunter
Lives in swamps and places with high humidity. To hunt, it enters the water and waits for insects and other small creatures to swim nearby on the surface. Feeling the vibrations, the spider breaks away and runs towards the source of the waves to grab its prey. The hunter's length grows up to 2.3 cm, the paw span reaches 8 cm.
Flower spider
Flower Spider
The spider has long front legs that can effectively grab prey. Males grow up to 4 mm in length, and females grow up to 9 mm. Females are white, sometimes with a yellow tint on their paws. Males are brown with red spots.
Interesting fact : the spider lives in the buds of different flowers, and its color can change depending on the color of the leaves. This helps to remain invisible while hunting insects.
Knitting spiders
Knitting spiders
Representatives of this species live in fields and prefer to settle near a water source. They spread their nets between branches over a river or pond and wait for various insects to get there. Knitting spiders mainly prefer flies, ants and aphids. Adults stretch up to several millimeters in length.
Haymaker
The Harvesting Spider
has a small round body and long thin legs. The color can be dark brown or with a reddish tint. The haymaker lives both in nature and in residential buildings. Builds webs in well-lit places, because... loves sunlight. Hunts small insects, but can also eat plant foods. It is completely harmless to humans.
Goliath tarantula
Goliath tarantula
An adult can grow up to 30 cm, making this species one of the largest among spiders. The body is covered with hairs, the color varies from light brown to dark colors. Most of the population lives in South America. The goliath tarantula is often kept as a pet. It feeds on insects and other spiders.
Interesting: Wasp
