Classification of the Phylum Arthropoda

Phylum called Arthropoda (arthropods) 
is the largest and most successful
of the
animal phyla. All arthropods
have segmented
bodies divided into
a head, jointed
legs and abdomen.

The major Classes of
living arthropods
are as follows with
one example each:
Class Arachnida -  spiders  
Class Crustacea -  crabs                                                                         

Merostoma- horseshoe crabs
Class Diplopoda -  millipedes 
Class Chilopoda -  centipede 
Class Insecta or Hexopoda - insects
Class trilobites are an extinct group
of arthropods that lived in the seas
of the
world for about 380 Mya (million years ago), from the Precambrian 610 Mya
to around the end of the Permian 230 Mya.
                Class Insecta – true insects are the most important members of the 
Arthropoda. Typical adult insects have
one pair of antennae, three
pairs of legs,
and three body regions:
head, thorax, and abdomen. The class
Insecta is divided
into some 29 to 40 major orders. Insects make up more than
half of all living things in the world. There are more than a million known species
of insects
and there are many more
waiting to be discovered.