Rarer still are the 250 to 350 species that are routinely exposed to ocean or seawater. Despite low numbers, many insect orders have members that can survive exposure to ocean water. Although each order is represented by only a few species, the diversity indicates that numerous orders have independantly evolved adaptations to salt water. The proportion of total species by insect order is shown in the chart below.
Flies are the most numerous and economically important species of marine insects.
However, their apparent dominance may be an artifact of their medical and social importance, or may reflect their ability as larvae to osmoregulate. Regardless of the reason, the disease-bearing mosquitoes, biting horse flies, deer flies, and midges have impeded the human development of millions of acres of coastal land. Here, a female Aedes aegypti takes a meal. Mosquitoes vector a number of diseases including malaria and yellow fever which are fatal to man. Of these habitats, the fewest insects are pelagic, and generally, the farther in shore, the greater the number of insect species.