Introduction

Abstract

Members of the phylum Arthropoda are the most numerous and widely distributed of all animal groups. They may be found in every part of the world and in every type of environment. Many, particularly those within the classes Insecta and Arachnida, live in close association with humans; others, while primarily parasites of animals, will readily attack or feed upon humans and some may be specifically adapted as human parasites. They may be of medical significance simply because of their physical attack and blood-sucking habits, or they may be of considerable importance as distributors of organisms that cause disease. These arthropod disease vectors may transfer pathogenic organisms in a purely mechanical manner from infected material to human food, or, more significantly, they may act as developmental vectors, incubating the disease organisms in their bodies before passing them on to uninfected hosts. Several arthropods, for example beetles, moths, cockroaches and mites, may be of considerable public health and economic importance, causing significant damage and nuisance by infesting and feeding on stored food and other commodities and infesting domestic situations.