Appendix IV : Medical Acarology and Entomology
Graham B. White
Most types of zoological organism (more than 90% of all known species) belong to the phylum Arthropoda, having an exoskeleton. Arthropods of medical interest belong to three classes: Arachnida (ticks, mites, scorpions and spiders; see below), Crustacea (crabs, crayfish, copepods, etc.) and especially the Insecta (insects), characterized by having the body subdivided as head (with antennae), thorax with legs and segmented abdomen.
TICKS AND MITESM. G. R. Varma
Class: ArachnidaThe arachnids differ from insects by lacking antennae and wings, and in having an unsegmented body. During the life cycle, they undergo incomplete metamorphosis; the eggs hatch into six-legged larvae which develop through the nymphal stage to adults. The nymphs and adults have four pairs of legs.
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