Porcelloderes impenetrabilis gen. & sp. n. (Hemiptera: Heteroptera: Reduviidae: Physoderinae) is described, based on males, females, and larvae from different localities in northeastern Tanzania. The new discovery extends the range of the subfamily (previously known from the Oriental Region and the Pacific, from Madagascar and neighbouring islands, and from Central and South America) to mainland Africa. In contrast to all previously described physoderine species, the new species is apterous, which is probably a result of neoteny; the neotenous aptery and its morphological consequences are discussed. The diagnosis of Physoderinae is extended in order to make it applicable to apterous taxa. In all examined specimens including larvae, the body surface is covered by a firm incrustation of soil, deposited between the long setigerous tubercles. This is the first record in the subfamily Physoderinae of camouflaging by application of material on the body, and the first report of such behaviour in the adult stage in Reduviidae.