What is an arthropod?

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April 14, 2016 10:18AM

The arthropods constitute over 90% of the animal kingdom and are classified in the phylum Arthropoda. They are distinguished from other animals by:

  • an exoskeleton (a skeleton on the outside of the body) body divided into distinct parts
  • jointed legs and appendages
  • bilateral symmetry (both sides of the body are the same)

Class Distinctions

Insects Grasshoppers, butterflies, beetles, ants, etc. 1,000,000 described world species:

  • three body regions: head, thorax, abdomen
  • six legs attached to the thorax (which has 3 segments)
  • adults with one or two pairs of wings attached to the thorax (some have none)
  • two antennae
  • lateral compound eyes

Arachnids Spiders, scorpions, ticks, mites, etc. 65,000 described world species:

  • two body regions (cephalothorax, abdomen)
  • eight legs
  • no antennae
  • Mouth parts are chelicerae (modified appendages) which in spiders are fangs

Crustaceans (technically a subphylum)

Classes include crabs, shrimps, lobsters, barnacles, isopods etc. 44,000 described world species:

  • two body regions
  • two pairs of antennae
  • 5 or more pairs of legs
  • primarily aquatic, few terrestrial

Chilopods Centipedes. 2,800 described world species:

  • well-defined head
  • first pair of legs modified for envenomation
  • flattened top to bottom
  • one pair of legs per segment
  • one pair of antennae

Diplopods Millipedes. 10,000 described world species:

  • two pairs of legs per segments, first four segments have 1 pair legs
  • one pair of antennae
  • well-defined head
  • usually cylindrical.

An arthropod is an invertebrate (meaning it lacks a backbone) with an external skeleton, a segmented body, and jointed appendages. Arthropods belong to the Phylum Arthropoda. Insects, arachnids, centipedes and crustaceans are all arthropods.

An arthropod is an invertabrate animal that has an exoskeleton, a segmented body, and jointed appendages. An ANTHROPOD is a bipedal humanoid (ie Homo Sapien, Homo Neanderthalus, Homo Habilus, Australopithicene Afarensis, and other hominids).

Arthropod is a family which includes insects and spiders.
Arthropods are Invertebrates (no backbone)

First of all, arthropods are NOT insects, insects are only a type of arthropod.

Arthropods are Split into 4 classes/groups.

Crustaceans: Have a hard shell (exoskeleton)

Many legs

No wings

One or 2 pairs of antennae

May live on land or water

Examples: Crabs, Lice, Lobster

Myriapods: Segments Present

1 or 2 pairs of legs per segment

Antennae (1 pair)

No wings

Examples: Centipede, Millipede

Arachnids: No antennae

2 body parts

8 legs (4 pairs)


No wings

Examples: Spiders, Scorpions, Ticks, Mites

Insects: Antennae Present

May have wings

6 legs (3 on each side)

3 body parts (head, thorax, abdomen)

Hope This helps

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January 24, 2015 4:10PM

Arthropods are animals which possess chitinous exoskeleton , jointed appendages , segmentation with tagmatization , open blood system , malpighian tubules . It is the largest group of animals . It includes insects, crustaceans , arachnids etc .