Malachiine beetles characteristically show “foetometamorphosis” during their life cycles, in which the first larval instar is inactive and nonfeeding. However, its adaptive significance has yet to be elucidated. The adaptive significance of hypermetamorphosis, another type of holometamorphosis characterized by a dramatic change of larval morphology from triungulin to eruciform larval stages, has been suggested to include protection, combat, host finding, foraging, and food acquisition. Given these observations from hypermetamorphosis, it is possible that foetometamorphosis is also related to the life cycle, foraging requirements, and larval structure of malachiine beetles; however, biological data on this matter is lacking. In this paper, the mature larval structures, bionomics and life cycles of Intybia pelegrini pelegrini (Pic, 1910) and Intybia takaraensis (Nakane, 1955) are presented for the first time. Based on observations, the unusual larval developmental pattern for both species is discussed.