8/3/2019 Medically Important Classes of Subphylum Arthropod A

http://slidepdf.com/reader/full/medically-important-classes-of-subphylum-arthropod-a 1/1

Medically Important Classes of Subphylum Arthropoda

Class Arachnida

There are approximately 57 000 known species of 

arachnids. Familiar arachnids include spiders, ticks and

mites. Arachnids have a pair of appendages called

chelicerae located near their mouths. Chelicerae are

modified into pincer in many species. In others, cheliceraeare modified into fangs that inject venom into prey.

Arachnids can generally be identified by the following

characteristics:

y  One or two body segments

y  Mouthparts adapted for slicing and

sucking (no chewing mouthparts)

y  Book lungs for breathing

y  Four pairs of walking legs

y  No antennae

y  Simple eyes

Class Chilopoda

Chilopoda is the lease diverse class of arthropods.

There are approximately 2500 known species of chilopods.

The most familiar member of the Class Chilopoda is the

centipede. Species are terrestrial and can be found

worldwide. They are carnivores and feed mainly on other

arthropods, snails, and worms. Chilopods can be identified

by the following characteristics:

y  Cylindrical, flattened body (made up of 

multiple segments)

y  Mouthparts adapted for chewing

y  Tracheal tubes for breathing

y  One pair of legs per body segment

(laterally located on the sides of the body)

y  One pair of antennae

y  Compound eyes

y  Claws

Class Crustacea

Class crustacean gets its name from the Latin

word crusta, meaning crust. There are approximately 35

000 known species of crustaceans. Familiar crustaceans

include lobsters, barnacles, and shrimp. Most species are

aquatic and live in marine environments. Crustaceans can

generally be identified by the following characteristics:

y  Two or three body sections

y  Exoskeleton made of tough chitin

y  Mouthparts adapted for chewing

y  Two pairs of antennae

y  Five or more pairs of walking legs

y  Compound eyes on movable stalks

y  Claws

Class Diplopoda

There are approximately 10 000 known species of

diplopods. The most familiar member of class diplopoda is

the millipede. All species are terrestrial and inhabit damp

forest floors. Diplopods are herbivores and feed on

decaying plant material. Diplopods can be identified by

the following characteristics:

y  Cylindrical body (made up of multiple

segments)

y  Mouthparts adapted for chewing

y  Tracheal tubes for breathing

y  Two pairs of legs per body segment

(ventrally located beneath the body)

y  One pair of antennae

y  Compound eyes

Class Insecta

Insecta is the most diverse class of arthropods

There are over 800 000 known species of insects, and an

estimated several millions yet undiscovered. Cockroaches

butterflies, and ants are some common insects. Most

insects live on land, although some freshwater aquatic

species exist. Insects can be identified by the following

characteristics:

y  Three body segments head, thorax and

abdomen

y  Mouthparts adapted for chewing, biting

sucking, and lapping

y Trachea for breathing

y  Two pairs of wings

y  One pair of antennae

y  Three pairs of walking legs

y  Compound eyes

Source:

http://www.mhhe.com/biosci/genbio/virtual_labs/BL_18/

BL_18.html