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The Order of Spiders (Araneae)

Spiders, grouped within the order Araneae, constitute one of the most fascinating groups in the animal kingdom. Present on every continent except Antarctica, they have colonized a wide variety of habitats—from humid forests to arid deserts, including human dwellings. Their anatomy is characterized by two main parts (cephalothorax and abdomen), eight legs, venomous chelicerae, and the ability to produce silk from spinnerets. Spiders have developed numerous hunting strategies: geometric webs, ground traps, ambushes, or chase hunting. Their morphological, behavioral, and ecological diversity is immense, with over 50,000 described species to date. This page serves as a general introduction to the order and guides to the main families and superfamilies covered on this site.

The Order of Spiders (Araneae) are arthropod invertebrates, with nearly 50,000 known species (2021). Only one species is primarily herbivorous.

They are not insects.

Their body is divided into two parts, called tagmata—the cephalothorax (prosoma) and the abdomen (opisthosoma).

Spiders have 8 legs and 6 to 8 eyes, simple or multiple.

Characteristics and Aspects of the Order Araneae:

General Anatomy:

Spiders have a body divided into two parts. The cephalothorax houses the eyes, chelicerae (venomous pincers), legs, and pedipalps (sensory and reproductive structures), while the abdomen contains internal organs.

Prosoma - Cephalothorax

3 to 4 pairs of eyes
2 chelicerae
4 pairs of legs
2 pedipalps

Opisthosoma - Abdomen

heart
lungs
intestine
digestive glands
silk glands
reproductive organs

Silk Secretion:

Spiders possess silk-producing glands called sericigenous glands. They use silk for building hunting webs, egg sacs, safety lines, etc.

A spider can produce up to 8 different types of silk: dry silk used as safety lines (draglines), framework threads or radial threads in orb webs, sticky silk forming the spiral to catch prey, cribellate silk with a velcro-like structure, parchment silk and cotton-like silk used for cocoon construction.

Diet:

Most spiders are carnivorous. They hunt prey by trapping them in webs, grabbing them directly, or using varied hunting strategies. Some species specialize in catching flying insects, while others feed on terrestrial arthropods.

Curiosity:

99.9% of spiders are carnivorous.
Only one known herbivorous spider: Bagheera kiplingi.

Venom:

Spider chelicerae inject paralytic venom into prey or predators. This venom liquefies the internal tissues of prey, allowing the spider to suck them up.

Reproduction:

Spider reproduction can involve complex courtship rituals, males offering prey gifts to females, and varied copulation mechanisms. Some species exhibit maternal care; others may be cannibalistic post-mating.

Webs:

Many spider species build webs to catch prey. Webs vary widely in shape, size, and complexity depending on the species’ feeding habits.

Orb Web

circular
radial spokes and sticky spiral

Sheet or Tangle Web

horizontal sheet with capture threads above
prey falls into the sheet where they are trapped

Funnel Web

funnel-shaped with a retreat tube
spiders wait for prey at the bottom of the funnel

Irregular or Chaotic Web

no clear pattern, often dense and tangled
to capture random prey

Tubular Web

forming tunnels or tubes
used to capture prey entering the tube

No Permanent Structure

Crab spiders (Thomisidae) and wolf spiders (Lycosidae) do not build webs to catch prey

The Order of Spiders (Araneae)

Classification into superfamilies is constantly changing due to phylogenetic research. Therefore, it is simpler to categorize the order by suborders, then by families.