Abstract
A new species of the genus Platydecticus is described based on adult male and female specimens and the egg. The new species, Platydecticus diaguita, inhabits the Andes Range at 27º S latitude, above 3000 m elevation. Both sexes are easily identifiable by genital morphology characters and by the external characters of the fastigium of the vertex and the reduced number of spines in the hind tibia. It is also the smallest species described for the genus.