We explain everything about spiders, where they live, what they eat and other characteristics. Also, which are the most poisonous spiders.
What are spiders?
Spiders are an immensely large and motley group of arthropods, related to scorpions, ticks, and mites (all members of the class arachnida) and very distantly with insects, with which it is important not to confuse them.
Spiders are animals with an important presence in our daily lives, constituting the seventh most diverse order of animals on the entire planet, with more than 46,500 different species classified to date.
In general, however, spiders are small to medium-sized arthropods, famous for their ability to produce a kind of silk (spider web) with which they weave nets or traps ready to hunt their prey, as they are important predators of small animals.
For this they have a poisonous sting capable of paralyzing their prey. However, given their enormous variety, spiders can have very different habits, colorations, habitats and levels of danger.
The human being has known spiders since time immemorial, and gave them a very important presence in culture. Not only as a symbol of industry, patience and perseverance, but also as ambassadors of predation, venomousness and danger, despite the fact that very few species actually pose a risk to human health.
According to the Roman Ovid (43 BC – 17 AD) in his Metamorphosis, the ancient Greeks told the myth of arachne, a spinner whose talents were such that she prided herself on being better than the gods, to the point of beating the goddess Minerva in a competition. The latter, offended not only by her defeat but because Arachne had woven various scenes of gods disguised as animals, turned her into a spider as punishment.
See also: Insectivorous animals
Spiders characteristics
In general, spiders are characterized by the following:
- Its dimensions generally range between 0.5 mm and 9 cm in length corporal, although there are exceptional cases of gigantic spiders, capable of reaching 30 cm.
- Since they do not have antennas, their most developed senses are those of touch and smell, which they exert through their first pair of appendages (pedipalps), since their sight is usually rather poor. Despite this, they usually have three to four pairs of eyes, arranged in a very varied way and color.
- In its posterior region they have glands capable of secreting a silk, composed of complex proteins, which in contact with air dry out and harden, forming the well-known “spider web”. The spiders are able to mold showy webs with it, or use it as an adhesive to make burrows, or as a method of preservation of their victims, wrapped in cloth to devour them later.
- Spider venom is made up of a specialized digestive enzyme, which paralyzes the victim and in many cases initiates a digestion process that liquefies the entrails and allows the spider to suck the contents of the victim without problem. Spiders generally have two types of venom: this paralyzing and another with greater effect, which they use to defend themselves from their multiple predators.
- Spiders have a very limited learning capacity, like most arthropods, but at the same time a wide range of instinctive or inherited behaviors, which allow them to imitate other species (ants or wasps, for example) or even lead an aquatic life (skating on the surface of the water, or diving into it with a bubble attached to the abdomen, like a diver). It all depends on the species.
They have a body composed of two parts:
- Cephalothorax (head and trunk in one), from which a pair of chelicerae (mouthparts) are born with which they inject poison into their prey.
- Abdomen, from which four pairs of articulated legs are born.
Where do spiders live?
Spiders have a massive presence on all continents except Antarctica, and in all climates and habitats, even in the cold. They are adapted to very different survival patterns, often at the top of the local food chain, although they also have numerous predators (birds, reptiles, mammals, etc.).
Likewise, many species have adapted to life alongside humans, occupying discreet corners of their homes, while many others maintain their wild life.
What do spiders eat?
They are predators par excellence. Whether they directly assault their prey, or wait patiently for them in the middle of their web, the diet of these animals consists of insects, other arachnids, worms, larvae, and even, in the larger species, small reptiles or rodents. Also famous are the cases of spiders in which the female, once the reproduction has been completed, devours the male.
How do spiders reproduce?
Spiders reproduce sexually, by laying eggs (oviparous reproduction), once the female has been fertilized by the male, inserting his sperm (actually spermatophores) into the female’s sexual tracts using one of his pedipalps.
To get there, the male must be very careful, since spiders usually consider food that is of the appropriate weight and size, and females are usually much larger than males. Thus, it is common for the male of some species to give the female “gifts”: animals wrapped in silk, so that she is distracted and does not devour it before it has fertilized her.
How long do spiders live?
Most spiders have relatively short life spans, rarely longer than a year. This, of course, depends on the individual species.
The most poisonous spider species
In a strict sense, all spiders are poisonous, except those belonging to the family Uloboridae, but very few represent a risk to humans, since the vast majority of them are incapable of penetrating human skin with their chelicerae to inject their venom. Those that actively hunt their prey are usually more poisonous than weaver spiders.
In general, in cases where a spider bite is received, it usually generates an unpleasant local reaction and nothing else; although many others have stinging villi capable of causing burning only with contact with the skin.
However, a few species possess such intense poisons that they are capable of producing severe poisoning or local necrotic reactions (tissue death) in humans, such as the Australian spiders of the genera Atrax and Hadronyche (about 35 species), or the small spiders of the genus Latrodectus and Loxosceles, more common and close to the human being.
The main endangered species are the following:
- Sydney spider (Atrax robustus), native to eastern Australia, measuring between 6 and 7 cm long, has a blue-black to bright brown coloration. Aggressive in behavior, they are one of the most poisonous spiders in the world, whose bite inoculates variable amounts of neurotoxins, very lethal in primates, although much less in chickens, dogs, cats and other domestic animals. Without specialized medical care, death can occur in 15 minutes to 3 days.
- Australian funnel spider (Modest hadronyche), native to caves and rocky regions of Australia, is together with the genus Atrax the most abundant and dangerous species on the continent. With nocturnal habits, they produce a poison similar to that of the black widow spider, which luckily has a specific serum with which to treat those affected.
- Southern black widow spider (Latrodectus mactans), the most famous spider in the world, typical of American countries such as the United States, Mexico and Venezuela, is a shiny carbon black color with a reddish hourglass-shaped spot on the lower abdomen. Females can measure up to 50 mm long and although they are nocturnal spiders, rather shy and solitary, the neurotoxic venom they produce is capable of paralyzing the central nervous system and producing enormous muscle pain, as well as triggering hypertensive episodes. However, with proper treatment it is rarely fatal.
- Fiddler spider (Loxosceles laeta), also called “Chilean recluse”, is the most dangerous species of its entire genus, whose bite injects proteinic and necrotic substances that can cause serious systemic reactions or death. Native to South America, it lives in hard-to-reach nooks and crannies, and is common in Chile, Peru, Ecuador, Bolivia, Argentina, Paraguay, Uruguay and eastern Brazil. It measures between 8 and 30 mm long, is brown and has a black violin-shaped line on the thorax.
- Banana spider (Phoneutria phera), for many the most poisonous spider in the world, is a large, wandering and aggressive species, capable of spanning the palm of a hand. Typical of the South American Amazon (Venezuela, Colombia, Peru, Bolivia, Ecuador, Brazil, and northern Argentina), it is capable of running at speeds of 40 kmph on its hairy legs, with light brown markings, and is recognizable by its chelicerae reddish brown. Its venom is capable of killing a person between 2 and 12 hours of effect without treatment, during which there is a loss of muscle control, severe pain, shortness of breath and risk of heart attack. Another known effect of its venom is to induce very painful and prolonged erections (lasting at least 4 hours) in men, capable of causing permanent physical damage.