Proasellus lescherae n.sp. is a little, interstitial species, living in the underflow of Rio Guadalope Basin (a tributary of Ebro River). It is related to the water-slaters of the underground waters of the Pyreneo-cantabrigian region (the phyletic line of ProaselIus spelaeus Racovitza). The mean size of the reproductive females is very small (2.9 mm) and the brood contains only 6-10 eggs. Nevertheless, the size of the eggs and intramarsupial larval stages are the same as in epigean or hypogean species of the genus, which reach a larger adult size.