We demonstrated nanopit formation by Ga-assisted local droplet etching technique in InGaAs metamorphic layers grown on vicinal GaAs(111)A substrates. We studied nanopit formation depending on the substrate temperature, Ga flux and Ga amount. The etched pits show a highly symmetrical pyramidal shape with an equilateral triangular base and the edges of the triangle are along < 1 1 0 > directions. The observed behavior, in terms of nanopit density, depth and, aspect ratio is well described by a model taking into account the dynamics of the droplet etching process