We compared the larval morphology of the genera Ataenius and Aphodius. The third larval instars of five Ataenius species: Ataenius opatrinus Harold, A. picinus Harold, A. platenis (Blanchard), A. simulator Harold and A. strigicauda Bates, are described or redescribed and illustrated. The most important morphological characteristics of the larvae of Ataenius are found in the respiratory plate of thoracic spiracle, the setation of venter of the last abdominal segment, the setation of the epicranial region and the morphology of the epipharynx. A key to larvae of the known species of Ataenius is included.