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THE part played by the female mosquito, or gnat, in the life-history of the germ of malaria, as well as in that of yellow fever, of filariasis, of dengue, and perhaps other diseases of warm climates, renders some knowledge of the natural history of this insect a necessity for the tropical pathologist. Although the Culicidæ or mosquitoes had received, now and again, some attention from naturalists ever since the time of Linnæus, it is but recently that the extent, complexity, and importance of this group of insects have been apprehended. Considerations of space preclude me from giving more than the merest outline of the subject; those who desire to follow it up would do well to provide themselves with one, or more, of five recent works namely, "The Mosquitoes of North and Central America and the West Indies," by Howard, Dyar, and Knab; Alcock's " Entomology for Medical Officers," Theobald's " Monograph of the Culicidæ," Blanchard's " Les Moustiques,"—— and Giles's " Handbook of the Gnats or Mosquitoes" in which will be found details of all that was known about these insects up to the date of their publication.

The Culicidæ, of which there are at least 500 known and, probably, over 200 additional and as yet undescribed species, belong to the order of Diptera, or two- winged insects, in which the posterior of the two pairs of wings of the typical insect are rudimentary, being represented by the halteres or balancers (Fig. 23). Like most other members of the order, they lay eggs, from which are hatched worm-like larvœ; these, after growth and several changes of skin, cease to eat, and become converted into nymphs