Arthropods - The World of Minibeasts

In taxonomic terms, minibeasts are part of the animal kingdom, as opposed to, for instance, to the plant kingdom. Within the kingdom of animals, they belong to the phylum Arthropoda, known simply as arthropods.

Arthropods move along by crawling. Crawling is the result of continuous shifting of a number of segmented legs.

The name "arthropods" means "segmented legs". The phylum is so named because their segmented legs are defining evolutionary features. Before arthropods evolved, the most sophisticated creatures belonged to the pylum Annelida, or segmented worms.

The annelids differ from even more primitive creatures because they have a body with regular segments (earthworms are a good example). This was the evolutionary development that, in taxonomic terms, seperated them from their immediate predecessors.

The annelids got as far as a segmented body, but they never developed legs, although some have bristles on the

undersides to increase friction against the ground. All they can do is wriggle.

The arthropods set a revolution in motion. They developed a leg consisting of segments: an upper thigh, a lower thigh and a foot, each of which was connected by a joint and could be moved by muscles. This enabled them to crawl.

Because they could crawl, arthropods discovered new ways of life and explored new niches. Consequently, a vast number of new species evolved. Even today about three quarters of the species on this planet belong to the phylum Arthropoda.

The phylum Arthropoda today consists of the sub-phylum Cruatacea (including crags, lobsters and shrimp) and several classes of including Arachnida (spiders, mites, scorpions etc.), Pantopoda (centipedes and millipedes - which are, by the way, not defined by the number of legs they have!) and Insecta.