Explanation of Names
from the Greek arthron (αρθρον)- "joint" + podos (ποδος)- "of foot, leg"; refers to the jointed legs of all members in the phylum
Numbers
17 classes
99 orders
About 2140 families
About 1.1 million described species (plus many more undescribed)
Size
ranges from the smallest mite (about 0.10 mm) and the smallest insect (a Hymenopteran,
Dicopomorpha echmepterygis at 0.139 mm), up to the King Crab (legspan more than 3.5 m)
most species of Arthropods are in the range 2-25 mm (or 1/12th to 1 inch)
Identification
Three or more pairs of jointed legs
Segmented body
Bilaterally symmetrical
Possessing an
exoskeleton, usually tough, composed in part of
chitin (1)
See
BugGuide Glossary for terminology.
Remarks
Arachnida belongs to subphylum Chelicerata, along with horseshoe crabs.
Insecta, Collembola, Diplura, Protura belong to subphylum
Hexapoda.
Chilopoda, Diplopoda, Symphyla, Pauropoda belong to subphylum
Myriapoda.
Branchiopoda, Malacostraca, Maxillopoda, and Ostracoda belong to subphylum
Crustacea.
Internet References
Introduction to the Arthropoda - overview of fossil record, life history, ecology, systematics, and morphology (Ben Waggoner and Allen Collins, U. of California Museum of Paleontology)
Tree of Life - starting page of Arthropoda taxonomic tree, with representative images, many literature references, and links to more info (David Maddison, U. of Arizona)
Modern Systematics of Insects - includes complete hierarchial listing of all higher taxa of Arthropoda, plus links to discussions on systematics (N. Kluge, St. Petersburg State U., Russia)
Insect Morphology - excellent illustrated glossary (U. of Minnesota, adapted from U. of Sydney, Australia)
