The fifth instar larva of Plectrocnemia laetabilis McLachlan, 1880 is described for the first time, and the main taxonomic characters are figured. The larvae of P. laetabilis are very similar to those of P. conspersa (Curtis, 1834), but they are easily distinguishable by some characters of the frontoclypeal apotome, labrum and abdominal segment IX. Additionally, some notes on distribution and ecological preferences are included.