The external female genitalia of 29 species belonging to three genera of Megalopodidae and 80 speciesbelonging to 61 genera of another four families in Chrysomeloidea were studied. The external femalegenitalia within the superfamily Chrysomeloidea can be divided into a cerambycid type and a chrysomelidtype. The comparative study of external female genitalia shows Megalopodidae is more closely related tothe family Cerambycidae than to the family Chrysomelidae s.l. Among five subfamilies of Cerambycidaewe studied, the subfamily Lamiinae is most closely allied to Megalopodidae. An evolutionary path is pro-posed for the spiculum gastrale in Chrysomeloidea: the characteristic state of the spiculum gastrale with-out a joint is primary, and that with a joint is secondary. The family Orsodacnidae has probably evolvedin isolation from the early chrysomelids, due to their shared external female genitalia (cerambycid type).In the family Chrysomelidae, the structure of external female genitalia and ovipositing behavior show thatthe subfamily Synetinae is closer to the Camptosomata than the subfamily Eumolpinae. In general, theshape of the terminal ovipositor is palp-like in the Chrysomeloidea. Terminal ovipositors are generallypalp-shaped in Chrysomeloidea except for those that are lamellate in the genus Callispa and the subfamilyCassidinae who produce egg-sheaths.