As in all insects, they differ very materially in each species of one genus. Those best known are the Anopheline eggs.
The eggs always float on the surface of the water; immersion soon destroys them, but many may occur in mud and can resist desiccation.
Fig. 397.—Types of scales, a to k; head and scutellar ornamentation, 1 to 5; forms of clypeus, 6. (Theobald.) 1, head and scutellum of Stegomyia, etc.; 2, of Culex and Mansonia; 3, of Howardina, Ædes, etc.; 4, of Megarhinus and Toxorhynchites, etc.; 5, of Cellia and some other Anophelines; 6, a′, clypeus of Culex; b′ of Stegomyia; c′, of Joblotia.
Characters of Adult Culicidæ.—The chief characters by which true mosquitoes, or Culicidæ, are known are the following:—
(1) Wings always with the veins covered with scales; the longitudinal veins, usually six in number (in one genus seven); the costal vein carried round the border of the wing.
(2) Head, thorax and abdomen usually, but not always (Anopheles, etc.), covered with scales.
(3) Mouth parts formed into a long piercing proboscis.
As a rule the males may be told from the females by their antennæ being plumose, whilst in the females they are pilose (vide fig. 394), but this does not invariably hold good, for in Deinocerites, Theobald, and Sabethes, Desvoidy, and others, they are pilose in both sexes. The labial palpi are very variable in regard to their form and the number of segments; in the Anophelina they are long in both sexes, as long or nearly so as the proboscis, more or less clubbed in the males; in Culicina, Joblotina and Heptaphlebomyia, they are long in the males, short in the females; in Ædeomyina, short in both sexes.