Abstract
The Chimarra lehibemavo group is described to include thirteen new species: Chimarra lehibemavo sp. nov., C. cebegepi sp. nov., C. fenoevo sp. nov., C. forcellinii sp. nov., C. fotobohitra sp. nov., C. gattolliati sp. nov., C. gensonae sp. nov., C. jejyorum sp. nov., C. hamatra sp. nov., C. makiorum sp. nov., C. moramanga sp. nov., C. saha sp. nov. and C. tamara sp. nov. The adults are easily recognizable by their large size, yellow colour and the structure of the male genitalia. The membranous tergum IX and the absence of the mesal lobe of tergum X are observed in other lineages, but the strong asymmetrical deformation of the phallotheca is apomorphic. The group is monophyletic with unknown affinities, but a preliminary phylogenetic placement is suggested following genetic analysis of two specimens. With one exception, the species have restricted geographical distributions in Madagascar and inhabit rivers in eastern pristine rainforests.