Insects are the largest class in the animal kingdom. They belong to the Phylum Arthropoda, which also includes spiders, crustaceans, ticks, centipedes and millipedes. All members of the phylum are characterized by having a segmented body and segmented legs. Insects and some other arthropods are the vectors of some of the most destructive diseases in the world, some of which are listed in Table 1. The vectors of disease that are of relevance to Australia are mosquitoes, flies, ticks and mites. Of these, mosquitoes are considered to be the most important.