arachno-, arachn- +
(Greek: spider; the arachnoidea; when used in medicine this Greek element refers to a membrane, veins, or any web-like structure in the body)
The very name Arachnida, the arthropod class to which the spiders belong, is derived from the story of the Greek maiden from Lydia, Arachne, who was so skilled as a weaver that she had the audacity to challenge the goddess Athena to a weaving contest.
Athena accepted the challenge and wove a tapestry depicting the majesty of the gods while Arachne wove one depicting the gods' amorous adventures or love affairs.
Enraged at the perfection of her rival's work, Athena tore it to shreds, which so upset the maiden that she hanged herself. Out of pity, Athena is said to have loosened the rope from around Arachne's neck which was turned into a cobweb, and Arachne was changed into a spider, doomed to spend the rest of her life weaving.
They are distinguished from insects by having four pairs of walking legs and by having the head and thorax in a single prosoma.
Many of the most important parasites and vectors of human and animal pathogens are included in this large assemblage.
More about Arthropoda
Along with the insects, crustaceans, centipedes, and millipedes; spiders are members of that group of animals without backbones referred to as the Arthropoda, literally the "jointed-limbed" animals.
Clearly they lack a backbone and instead have an external skeleton, called an exoskeleton, which has some similarities to a suit of armor; it is tough and fairly rigid and the muscles are attached to it internally.
Like the vertebrate skeleton, that of the arthopods is designed as a compromise between rigidity, to provide support and protection for the soft, delicate internal organs, and flexibility, to allow for ease of movement.
Also called spider poisoning, arachnoidism, and araneism.
2. The spinning apparatus of a spider, including spinning glands and spinnerets.
The most striking physical properties of spider silk are its strength and elasticity. It has been found that a thread .01 centimetre in diameter will support a weight of 80 grammes before breaking, and will stretch by over twenty per cent of its original length.