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.
Athena wove into her web the stories of those who had aroused the anger of the gods, while Arachne chose stories of the errors of the gods.
Enraged at the excellence of the work, Athena tore Arachne's web into pieces. Arachne hanged herself in grief and was transformed by Athena into a spider.
This was adopted as the spider family in science which includes scorpions, mites, and ticks.
The term arachnoid refers to anything that resembles a spider's web.