Tethina pictipennis Freidberg and Beschovski, 1996 is a North African (Morocco) species strongly characterized mainly by having patterned wings. So far it was the only species in the family to have such a peculiar character state. Unexpectedly, a second species with spotted wings was collected by two of the authors (J.A., R.A.) in a beach of northern Portugal. At first glance it strongly resembles T. pictipennis as to shape, colour, and wings bearing black spots, but it substantially differs from the latter species by having a combination of external and genitalic features that makes it unique within the entire family Canacidae. Besides the spotted wings (a character state which is shared with T. pictipennis only), it lacks postocellar and katepisternal setae and all setulae of head and thorax are lacking as well. Furthermore, an unusually long, narrow, genital postgonite characterizes the male terminalia. This sclerite is so much long that it even protrudes, as a rodlike projection, outside the postabdomen in dry and alcohol specimens.
Both these species, T. pictipennis and T. lusitanica, belong to the alboguttata-group, a group of species with depigmented (white) crossveins (but pigmented in the new species), sometimes surrounded by a milky halo, surstylus with more or less broad ventral lobe, and female cercus bearing numerous, stout, curved spinulae. Additionally, the two species have patterned wings, a character state unique among the canacids, as well as the gena bearing a few, scattered, microscopical setulae like those occurring on the gena of the species of em>Pelomyiella Hendel (Pelomyiinae). The occurrence of the latter character in species of both the subfamilies Tethininae and Pelomyiinae has arisen independently more than once. In the new species described herein these tiny hairs are mostly located on the anterior corner of gena, whereas they are generally more widely distributed on the gena of T. pictipennis. These characters single out the two species as a monophyletic lineage, likely evolved in the westernmost area of the alboguttata-group. The absence of some main setae and setulae in the new species (see diagnosis below) distinguishes it from all congeners. This peculiarity is probably due to an autapomorphic character reversal. A phylogenetic analysis on this species group will hopefully clarify their taxonomic position in a more consistent way.
The specimens, inhabiting a sandy beach characterized by heavy anthropical pressure, were observed in nature, photographed, video recorded (see: http://www.youtube.com/user/tethinaportugal) and finally collected and preserved in alcohol.