Answer
The phylum Arthropoda ( jointed feet animals) includes such animals as insects, crustaceans, spiders, scorpions, millipedes, centipedes, mites and ticks.
There are four living (extant) subphyla and one extinct subphylum in the Arthropoda.:
The living subphyla are Chelicerata, Crustacea , Myriapoda, and Hexapoda. Trilobites (Trilobata) make up the single fossil subphylum.
Examples of animals in the Chelicerata are horseshoe crabs, spiders, ticks and scorpions. Centipedes and millipedes are common Myriapoda. The Crustacea includes crayfish, lobsters, crabs and barnacles. Insecta -- ants, termites, mosquitoes and others--is the main class of the Hexapoda. However, the less numerous Entognatha (class)--spring tails, and snow flies-- also belongs to the Hexapoda.
Work Step by Step
Trilobites belong to an extinct subphylum of the Arthrpoda. they wer bundant in the Cambrian and Ordovician but died out 200 million years ago. The trilobite body was divided int three lobes by two longitidinal grooves. They were most likely bottom feeding scavengers.
The Chelicerae had bodies that were divided int two tagmata --cephalothorax and abdomen. They do not have a mandible and antennae were absent. Instead they have chelicerae ( onepair); pedipalps ( 1 pair), and four pairs of walking legs. Spiders, scorpions, ticks and mites belong to the Chelicerata.
The Myriapoda have bodies that are divided into two tagmata*-- head and trunk. Centipedes and millipedes belong to this subphylum.
Crustaceans are mainly aquatic ( marine and freshwater); crayfish, lobsters, crabs , barnacles are members of this subphylum.
The Hexapoda which is the largest subphylum, comprises the very numerous Insecta and the less well-known Entognatha--springtails , snow flies and Japygids ( Diplura). Mosguitoes, houseflies, butterflies, grasshoppers moths, ants , termites, and bed bugs (Cimex) are some common insects.
* Tagmata( sing. tagma). A tagma is a compound body division of an arthropod, formed by embryonic fusion of two or more segments. Some examples of tagmata are head, thorax ,abdomen and cephalothorax.
