Spider

Spiders are eight-legged arachnids that live across almost all of Earth aside from Antarctica. As of 2022, there are nearly 50,000 species of spiders living across nearly every major biome. Spiders range from incredibly tiny – the smallest spider is a fraction of the size of a pinhead – to giant spiders that can measure a foot across.

Spider Facts

• The largest spider in the world is the giant huntsman spider. It measures a foot wide when you count its leg span. Incredibly, this spider was only discovered this century and lives in caves in the country of Laos.
• The oldest known spider lived to be 43 years old. It was a trapdoor spider in Australia and didn’t even die from old age. Instead, it was killed by a tarantula hawk that laid its eggs in the spider.
• How’s this for dedication? The black lace-weaver spider has evolved so spiderlings that hatch eat their mother alive. The name for offspring consuming their mothers is named “matriphagy” and is displayed in several spider species.
• A spider named Darwin’s bark spider produces a web that’s 10-fold stronger than Kevlar. Its silk is the toughest biological material ever discovered.
• Are spiders masters of disguise? More than 300 species put their front legs on the top of their heads to disguise themselves as ants. This behavior helps them both avoid and eat ants.

Scientific Name

What is the scientific name for spiders? The scientific name for spiders is Araneae, and they are air-breathing arthropods with eight legs, fangs that can inject venom, and spinnerets that secrete silk. This group of arachnids is one of the most diverse among all living organisms and can be found on every continent except Antarctica. As of today, 50,356 spider species have been recorded and categorized into 132 families, though there is some debate among scientists about how these should be classified, with over 20 different classifications proposed. A group of spiders is known as a cluster, clutter, or sometimes a colony.

Appearance and Behavior

The physical makeup of spiders is distinct from other arthropods in that their typical body parts are combined into two sections, a cephalothorax, and an abdomen, connected by a thin tube-like pedicel. This naming of this structure has been disputed, as there is no fossil or embryonic evidence to suggest that the head and thorax were ever separated. The abdomen of each spider contains the heart and breathing organs. All spiders have eight legs. Many of them have fangs that can excrete a venomous substance.

Spiders have silk-spinning organs called spinnerets on their forelegs or under their abdomen. Some spiders have six, two, four, or eight spinnerets that they can move in unison or separately as they so desire. The spinnerets do not only release one thread of silk but are complex and contain many spigots that each release a fine stream of silk. Spiders can also produce different types of silk for different types of projects or combine silks to make them stronger. Some spiders have very large spinnerets consisting of a spigot that stretches the length of their abdomen, such as the desert grass spider.

Spiders use their silk for various purposes, such as building webs to live in, building webs to catch prey, constructing egg sacs, transferring sperm, encapsulating insects, creating balloons to fly, weaving structures to protect themselves from predators, assembling cocoons and manipulating static electricity in the air.

Spiders differ from insects in that they do not have antennae. Most spiders have a highly centralized nervous system, meaning that all their ganglia are joined together in the cephalothorax. Additionally, spiders do not use their extensor muscles to extend their limbs but rather rely on hydraulic pressure.

Evolution and Origins

Humans have been around for a much shorter period of time than spiders, who likely evolved approximately 400 million years ago. The earliest spiders were likely descended from arachnids that had recently left their aquatic homes. Fossils like Attercopus fimbriungus, which lived 380 million years ago during the Devonian Period, demonstrate that spiders existed long before the dinosaurs.

The earliest segmented spider fossils belonged to the Mesothelae group, which had spinnerets positioned in the middle of their abdomens instead of at the end, like modern spiders. It is thought they were predators on the ground, living amongst fern and moss during the Palaeozoic era and hunting primitive creatures like slaters, millipedes, silverfish, and cockroaches. It is possible that these spiders used silk for protection for their eggs, to line a shelter hole, and later for constructing sheet webs and trapdoors.

As plants and insects evolved, so did spiders’ use of silk. Spiders with spinnerets on their abdomens (Opisthothelae) emerged over 250 million years ago, which likely encouraged the production of more complex webs to capture prey on the ground and in trees. During the Jurassic Period, when dinosaurs roamed the planet, orb-weaving spiders developed aerial webs to catch the increasing variety of flying insects. Additionally, hunting spiders in different habitats also started to diversify in order to catch more prey and occupy more habitats.

The fossil record of spiders is not very extensive. However, amber fossils of spiders, which are complete spiders trapped in tree resin, show us that a spider population similar to today’s existed 30 million years ago. Additionally, segmented spiders have survived in East Asia since the late Palaeozoic period until now. They live in caves and burrows and build trapdoors over them. They have not changed much from their ancestors.

Habitat

There are a variety of habitats where spiders can be found. Most species of spiders prefer living outdoors, where they build webs or hunt for prey on the ground or among vegetation. Common outdoor habitats include forests, fields, gardens, and deserts.

Spiders can also live indoors, particularly in areas such as basements and attics that are dark and undisturbed by humans. Additionally, many species of spiders will make their homes near water sources like ponds and streams in order to have easy access to food sources like insects that congregate around bodies of water.

Lastly, some aquatic spider species inhabit freshwater rivers and lakes, where they hang out underwater by weaving air bubbles into silken nests from which they breathe oxygen while submerged beneath the surface.

Diet

Spiders are carnivores and feed mainly on insects, usually their own prey. Depending on the species, they can also consume other spiders, small mammals, and reptiles. For most of them, however, the main food sources are flying or crawling insects such as flies, moths, and ants. Some spider species will even eat small amphibians or fish if they come across them.

The type of diet for a particular spider species depends largely on its size; larger spiders have more options when it comes to potential prey items than smaller ones do. A few types of spiders survive solely by scavenging dead animals or consuming nectar from plants instead of living organisms like insects. In addition to these dietary habits, some spiders use toxins in the form of venom injected into their victims to make them easier to digest before consuming them whole.

Predators

Spiders are voracious predators, but what animals eat spiders? With the vast majority of spiders being less than a couple of inches in width, the main answer is that animals that also eat smaller insects will eat spiders as well. Animals like frogs, birds, and lizards are top predators of spiders.

In a controlled simulation meant to mimic conditions on an island, researchers tested spider populations with and without lizards. They found that after four days without lizards, 65% of spiders had survived. However, when lizards were introduced, only 40% of spiders remained at the end of the study. This is to say; lizards can deplete spider populations very rapidly.

Other animals that eat spiders are fish, snakes, toads, tarantula hawks, scorpions, spider wasps, centipedes, other spiders, bats, and small mammals like shrews.

It is also important to know that despite spiders being part of the diet of snakes, there are some species of spiders that eat snakes.

Reproduction and Lifecycle

Spiders reproduce in a variety of ways, depending on the species. Most spiders lay eggs and store them in silken egg sacs that are either attached to their webs or carried by the female until they hatch. Female spiders can also produce live young without fertilization, though this is more common in some species than others.

Once hatched, baby spiders go through several stages of growth before becoming adults. During these stages, called instars, they shed their exoskeleton multiple times as they grow bigger and stronger. After reaching adulthood, most spiders will only live for one or two years before dying off naturally due to old age or predation from other animals.

Conservation and Population

There are a variety of threats that have led to the endangerment of 27 species of spiders. These include habitat loss or fragmentation due to human development, climate change, pollution, and disease. Loss or degradation of their habitats can cause significant population decline for these species as they struggle to survive in a new environment. Pesticides used on crops can also be toxic to spiders, reducing populations and even leading to extinction in some cases.

Two examples of endangered spider species are the Regal Jumping Spider (Phidippus regius) and the Hentz Orbweaver (Neoscona crucifera). The Regal Jumping Spider is native to North America and is threatened by the destruction or alteration of its natural habitat due to urban development. The Hentz Orbweaver is found primarily in the southeastern United States and faces similar threats from land-use changes caused by humans, such as deforestation for livestock grazing and urban sprawl.