The third, or _Anopheles_, sub-family is that concerned in the transmission of human malaria, and, as may be seen by comparing the two lower photographs of the plate with the upper ones, can easily be recognised by their characteristic form and attitude. In these mosquitoes the feelers are long and thick in both sexes, and as they are held habitually in contact with the proboscis, these together appear to the naked eye as a prolongation of the body as thick, or thicker, than the abdomen. Moreover, except in a few species, their position, when resting, forms a singular contrast to that of the _Culices_, the whole body and proboscis being held in one straight line, with the abdomen raised from, and the proboscis pointed almost vertically at the surface on which they rest, and almost touching it with its point, as if they were preparing to drive the latter into it; so that, viewed with the naked eye, they look much like minute black thorns, stuck into the surface on which they are sitting. On closer examination, it will be seen that the wings are not plain, but spotted (the number of plain-winged species being unimportant). [Illustration: FIG. 10.--Wings of various sorts of _Anopheles_ mosquitoes, much magnified, to show the arrangement of the dark and light scales which form the characteristic spots.] The appearance of spotting is usually produced by alternate lengths of the veins of the wings being coloured in finely contrasted dark brown or black, and white or yellow, and varies, of course, in detail in different species, but the above figures of the wings of some of the commoner Indian forms will give an idea of the general effect, as seen under a moderate magnification, for though the spots are quite visible to the naked eye, it requires a fairly powerful hand lens to make out the details properly. Like the _Stegomyiæ_, the _Anophelinæ_ are only common during the rains, but stray specimens will be met with for a month or two afterwards; and though they practically disappear during cold weather, a few may be generally met with during the hot dry months of continental hot climates. From what has been said, it follows that the prevalence of malaria, like that of mosquitoes, must necessarily be seasonal. The survival of the malarial parasite at those times of the year when mosquitoes are scarce or absent, is maintained by the persistence of considerable numbers in a latent condition, in the persons of human beings who have been imperfectly cured of an attack of malaria. Cases of this sort, which have either been never treated at all, or in which the administration of quinine has been stopped too soon, are extremely common in all malaria-stricken communities, and such persons are always liable to relapses if they are brought below _par_ by any depressing influence, such as chill, too great exposure to the sun, or the incidence of injuries, or of other diseases.