The morphology of the larval stages of Arrenurus nodosus, A. knauthei and A. stecki is described. Particular attention is paid to the different characters separating the three species. The larvae of the three species differ in the size and shape of the dorsal plate. Distinct differences appear between the proportions in the length of the lateral margins of the epimeres, which are similar in A. knauthei and A. stecki, but different in A. nodosus. There are differences in the shape of the excretory pore plates. In A. stecki the shape of the anal plate is slightly different owing to the truncated proleg. The structure of the pedipalps are very similar. The PIII1 setae are always bipectinate, the PIV1 is pectinate in A. knauthei and smooth in the other species, the PV6 is short and thick in A. nodosus, and long and thin in the other two species. Distinct differences also occur in the feathering of legs. The ITi8 seta is short in A. knauthei and long in the other two, the LITi10 seta is long in A. nodosus and short in the other two, and IIITi10 is thick and pectinate in A. nodosus, and smooth and fairly thin in the other two.