Phylum Arthropoda (Gr. arthros = joint; pods = foot) contains the great majority of the known animals, about one million species, and many of them are enormously abundant as individuals. It includes such common and well-known forms as the crabs, shrimps, insects, spiders, scorpions, ticks, centipedes, as well as a host of other less familiar forms. The Crustacea, Arachnida and Insecta are kept under an independent group, the Arthropoda. Arthropoda are triploblastic, bilaterally symmetrical, metamerically segmented animals. Body segments usually bear paired lateral and jointed appendages. Digestive system complete; mouthparts adapted for various modes of feeding. Circulatory system open with a dorsal heart, arteries and blood sinuses. Respiration by general body surface, gills, tracheae or book-lungs. Excretory organs are green glands or Malpighian tubules. Xervous system with a dorsal nerve ring and a double ventral nerve cord. Sexes are general separate and sexual dimorphism is often exhibited by several forms. Fertilization is internal. Development is usually indirect through larval stages. This work in three volumes contains encyclopaedic information on the phylum Arthropoda. The entire information is presented scientifically. Profusely illustrated the authoritative information gathered herein will prove of utmost use to students, teachers ar.d researchers in the field concerned
