External genitalia, tergum 9, tergoanal sclerite, and spiculum gastrale of 54 species, representing 50 genera from various parts of the world, were studied. The female genitalia consist of a pair of valvifers, which are confined to segment 9. The valvifer may be narrower or broader distally or of uniform width. The stylus may be present or absent; when present, it may be elongate, moderately developed, reduced or rudimentary. The loss of stylus seems to be more common in the subfamily Nemognathinae. The principal components of the male genitalia are a pair of parameres, and a median aedeagus. The parameres are separate dorsally but are fused ventrally at their bases with each other and with the phallobase. The distal ends of the parameres are generally curved ventrally. The phallobase may or may not possess an angular protuberance. The latter, when present, is near the base in most species and may be prominent, moderately developed, or poorly developed. The phallobase has an apodeme, which may be broader or narrower than, or as broad as the base of the phallobase. The aedeagus is well sclerotized, except for a portion of its dorsal wall near its base, and possesses single or double dorsal and ventral aedeagal spines. The aedeagal spines are absent in the subfamily Nemognathinae. The relative position and shape of the aedeagal spines are subject to considerable variation among the species studied. The apodeme of the aedeagus is generally well developed in the Meloinae and reduced in Nemognathinae. Tergum 9, tergoanal sclerites, and the spiculum gastrale, although not a part of the genitalia, are associated with the genitalic musculature. Tergum 9 shows several variations in degree and extent of its sclerotization either in one sex or in both. The setae on T9 are present in most species, lacking only in a few. Furthermore, they may be present or absent either in only one sex or in both. The tergoanal sclerites are situated dorsolaterally at each side of T9 and the anus. This sclerite is usually well developed, although it may be reduced, indistinguishable, or absent. The shape of this sclerite shows considerable variation. Generally, setae are present on the tergoanal sclerite, but they may be indistinguishable or absent. The spiculum gastrale is situated beneath the genital chamber in the male. The arms of the spiculum gastrale may be long, short, or of unequal length, rudimentary or absent. They may be curved laterally (Meloinae) or bowed mediolaterally (Nemognathinae). Their apices may be pointed, broadened, rounded, notched, concave, or denticulate. The base of the arms may or may not be bulbous. The junction of the arms may be moderately or more bulbous. In a few species, the junction of the arms possesses posteriad protuberances, which may be rudimentary, small, or greatly developed. The posterior margins of the arms may be smooth or denticulate. The shaft is usually long, but it may be short or considerably reduced. It may be straight or tapering, bent in middle or beyond middle, slightly curved, and slightly or broadly sinuate. The apex may be pointed, rounded, or spatulate. Furthermore, near its apex, the shaft may be bent, recurved slightly, more curved, or slightly sinuate.