1) Chilopoda :
1. Phylum Arthropoda includes this group Chilopoda.
2. Chilopoda includes centipedes.
3. These are dorso - ventrally flattened, distinctly segmented arthropods.
4. The body shows 2 divisions. 1. head and 2. long trunk.
5. The head bears a pair of long, many jointed, sensory antennae, a pair of eyes, a pair of toothed mandibles and two pairs of maxillae.
6. The mouth lies on the ventral side near the anterior border of the head.
7. The trunk contains 15-173 segments in different species.
8. Each segment has a flat tergum on the dorsal side, sternum on the ventral side.
9. Each trunk segment, except the last two, bears on its lateral sides a pair of legs. They are modified into stout poison claws or maxillipedes. They are used for killing the prey.
10. The anus is situated at the extreme end of the trunk.
11. There is a single genital opening.
12. The genital opening opens in front of the anus on the ventral side of thepenultimate segment.
13. A pair of long Malphighian take up excretion.
14. Tracheae serve as respiratory organs.
15. Sexes are separate, there is a single gonad above the alimentary canal. Ex : Scolopendra.
2. Diplopoda :
1. Phylum Arthropoda includes this class.
2. The class diplopoda includes the millipedes,
3. These are long, cylindrical, segmented arthropods.
4. Body has 3 divisions, head, thorax and abdomen.
5. The head bears a pair of short, 7 jointed antennae, a pair of eyes, a pair of mandibles and a pair of maxillae.
6. The maxillae are fused with the first thoracic sternum to form a large labium like structure called the Ganthochilarium.
7. The mouth lies between the mandibles.
8. The thorax is short and consists of four single segments.
9. Each segment has an arched tergum and a small flat sternum.
10. The abdomen is long and comprises 20 to 103 segments.
11. Each segment bears two pairs of 7 jointed legs.
12. The third abdominal segment bears in the male a pair of short gonads or auxilliary compulatory organs.
13. There are two genital apertures that open out towards the anterior end on the third segment close to the second pair of legs (Progoneata).
14. A pair of long malphighian tubules take up excretion.
15. Tracheae will serve as respiratory organs.
16. Sexes are separate. Ex : Julus