Nearly zoo genera and about 700 species of mosquitoes are now recognized, but in all probability the total number of species is not less than 1000.
Of insects there are relatively few kinds; but ants, beetles and mosquitoes abound.
Following up this line of investigation, Major Ronald Ross in 1895 found that if a mosquito sucked blood containing the parasites they soon began to throw out flagellae, which broke away and became free; and in 1897 he discovered peculiar pigmented cells, which afterwards turned out to be the parasites of aestivo-autumnal malaria in an early stage of development, within the stomachwall of mosquitoes which had been fed on malarial blood.
Should the summer be very cool and the mosquitoes few, the Lapp finds it next to impossible to bring the creatures together.
In tropical climates with a well-marked dry season mosquitoes pass into a semi-dormant condition during the period when there is little water in which to deposit their eggs.
The result has been that in subsequent years mosquitoes have been collected, studied and described by naturalists and medical men in all parts of the globe.
Other flies act as diseasecarriers, including the mosquitoes (Anopheles), which not only carry malarial germs, but also form a secondary host for these parasites.
He further found that only mosquitoes of the genus Anopheles had these cells, and that they did not get them when fed on healthy blood.
Perhaps the converse is more feasible in some circumstances - that is to say, preventing mosquitoes from having access to malarial persons, and so propagating the parasite in themsevles.
Gadflies and mosquitoes are a veritable plague around the lakes of the lowlands in the hot weather.