Iais pubescens is a species of marine isopod in the family Janiridae.

[1] It inhabits seashores in a large number of locations in the southern hemisphere and may be found both free-living, and as commensals on larger isopods.

[2] I. pubescens may be encountered both free-living in the inter-tidal and sub-tidal zone, at depths of up to 5 m, and as a commensal in the brood pouch of larger isopods.

[3] The species has evolved an unusual mating system (documented in commensal-living individuals) that involves males actively seeking out newly born virgin females and retaining them in their own brood pouches for several days, fertilizing and releasing them shortly after their first moult.

This pattern may have evolved in response to low encounter probabilities between sexes when carried around on their highly mobile hosts.