Phylum Arthropoda: General Characteristics and Classification

Insects, spiders, crustaceans, and other invertebrates are all members of the phylum Arthropoda. Arthropods are the most numerous creatures on Earth, with over a million identified species. They are important pollinators, decomposers, and prey for other creatures in ecosystems. Arthropods have a strong exoskeleton and segmented body, allowing them to adapt to a variety of settings. Understanding the biology and behavior of arthropods is critical for pest species management, drug development, and ecological study.

Characteristics of Arthropoda

Gr. Arthos : Jointed         podos: legs

  • Animals with jointed legs
  • Largest phylum in Animal kingdom in both number of taxa and biomass
  • Most successful group of  animals due to chitinous skeleton.
  • Bilaterally symmetrical, triploblastic, metamerically segmented and tagmatization
  • Segments are not separated as in annelids; external segmentation is present.
  • Organ system level of body organization.
  • Body is divided into three tagmata : head , thorax and abdomen ; Head and thorax are fused in some animals called cephalothorax
  • Reduced coelom in adult ; body cavity consists of haemocoel ; so called haemocoelomate.
  • Alimentary canal completing consisting of foregut, midgut and hindgut.
  • Mouthparts adapted for various modes of feeding :
  • Biting and chewing type :   Cockroach , grasshopper etc.
  • Chewing and lapping :         Bees and wasps
  • Piercing and sucking :          Bugs, Aphids, Mosquitoes
  • Sponging :                              Housefly
  • Siphoning :                           Butterflies and moths
  • Circulatory system open type with dorsal contractile heart.
  • Respiration by general body surface or special structure such as gills, trachea or book lungs.
  • Excretory system are coxal glands, green or maxillary (in aquatic forms) and Malpighian tubules (in terrestrial forms).
  • Major excretory product is uric acid
  • Nervous system with dorsal nerve ring and a double ventral nerve cord.
  • Sense organs comprise antennae, simple eyes, compound eyes, statocysts, chemoreceptors and taste receptors.
  • Usually dioecious. Fertilization internal.
  • Majority are oviparous, few like scorpios are ovoviviparous.
  • Development direct or indirect, one to many larval stages, parthenogenesis in some.

Classification of Arthropoda

Subphylum 1 : ONYCHOPHORA

  • Most primitive ; commonly called velvet worms or walking worms
  • eg : Peripatus (connecting link of arthropods and annelids)


  • These are fossil arthropods

Subphylum 3 : CHELICERATA

  • 1st pair of appendages are chelicerae , second pair are pedipalps.
  • Body divided into prosoma (cephalothorax) and opisthosoma (abdomen)

Subphylum 4: MANDIBULATA

  • Body divided into head, thorax and abdomen, have one or 2 pairs of antennae, a pair of jawa (mandibles), one or two pairs of maxillae

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Binod G C

I'm Binod G C (MSc), a PhD candidate in cell and molecular biology who works as a biology educator and enjoys scientific blogging. My proclivity for blogging is intended to make notes and study materials more accessible to students.

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