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Class

Character

Crustacea

Chilopoda(Centipedes)

Diplopoda(Millipedes)

Insecta

(Largest class in animal kingdom)

Arachnida

Merostomata

Habitat

Mostly marine but a few live in freshwater or moist places, some are parasites.

Terrestrial

Terrestrial

Mostly terrestrial, rarely aquatic

Mostly terrestrial

Mostly marine

Body segments

Body consists of cephalothorax (covered by carapace in some) and abdomen.

Body elongated, dorsoventrally compressed and divisible into head and trunk.

Body elongated,sub-cylindrical and divisible into head, thorax and abdomen.

Head, thorax and abdomen

Cephalothorax and abdomen

Cephalothorax and abdomen

Appendages

Each body segment bears a pair of biramous appendages which are variously modified for feeding, swimming, respiration and reproduction. Appendages are present on abdomen as well as thorax.

Each trunk segment bears a pair of jointed legs, terminating into claws. First pair of legs bear poison apparatus.

Each abdominal segment bears two pairs of jointed legs.

There are three pairs of legs in the thorax and two pairs of thoracic wings which may be absent in some. Abdomen is with appendages.

Four pairs of legs are present over cephalothorax. Abdomen is without appendages.

Cephalothorax bears a pair of chelicera and five pairs of chelate legs. Five-six pairs of abdominal appendages are also present. Abdomen ends in a sharp telson or spine.

Mouth parts

Chewing type

Chewing type

Chewing type

Various types

e.g

.,

siphoning, sucking etc.

Sucking type

Sucking type

Respiratory organ

Body surface or gills

Tracheae

Tracheae

Tracheae

Book lungs, tracheae or both

Book gills

Excretory organ

Green glands

Malpighian tubules

Malpighian tubules

Malpighian tubules

Malpighian tubules and coxal glands

Coxal glands

Antennae

Two pairs

One pair

One pair

One pair

Absent

Absent

Eyes

Compound eyes

Absent or one to many ocelli, compound eyes are present in centipedes.

Simple eyes

Compound eyes

Simple eyes

Median, simple and lateral compound eyes

Reproduction

Sexes separate, Development is usually indirect. Characteristic larva is nauplius.

Sexes separate.Development direct.

Sexes separate.Development direct.

Sexes separate.Development may be direct or indirect.

Sexes separate.Development is generally direct.

Sexes separate. Development indirect.

Examples

Prawn, Crab, Crayfish,

Daphnia

,

Cyclops

, Shrimp, Lobsters etc.

Scolopendra, Scutigera

,

Lithobius etc.

Spirobolus, Julus

etc.

Cockroach,

Apis

Bombyx

, Mosquitoes,

Housefly, Butterfly etc.

Scorpion, Spider, Tick, Mite etc.

Limulus,Eurypterus,Pterygotus

.

Table :

Some important classes of Phylum Arthropoda and their main characteristics