Aenigmatrichia, Wells & De Moor, 2020

Wells, Alice & De Moor, Ferdinand C., 2020, Hydroptilidae (Trichoptera) of Angola, a new genus, seven new species, and five new records, Zootaxa 4868 (4), pp. 495-514 : 503-504

Genus Aenigmatrichia gen. nov.

Type species: Aenigmatrichia asymmetrica sp. nov., here designated.

Diagnosis. Assigned to subfamily Hydroptilinae , members of this genus share a combination of features with the monotypic Tanzanian genus Tangatrichia Wells & Andersen 1995 , having three ocelli; the antennal flagellomeres are as in Oxyethira species with a basal whorl of clothing hair and scattered sensilla auricillica, without sensilla placodea; each forewing is without a jugal lobe; the tibial spur formula is 0,3,4; and the metascutellum is triangular. However, the males differ significantly, with the structure of the terminal abdominal segments showing superficial resemblance to those of Pseudoxyethira: Anteroventral margins of segments VIII and IX produced, rounded and retracted well within VII, not in the form of slender apodemes; externally having abdominal segment VIII deeply cleft mid-ventrally and forming elongate lateral lobes flanking paired lightly sclerotised rod-shaped structures, interpreted as inferior appendages; the ventral plate is well developed; and the phallus has a median titillator and the apex flared.

Among females collected with the males is a single equally unusual one, here assumed to be that of Aenigmatrichia asymmetrica sp. nov. and distinguished from other known females by the prominent conical ventral structure interpreted as abdominal sternite VIII.

Etymology. The generic name Aenigmatrichia , with feminine gender, was chosen because this taxon is an enigma, exhibiting features of both Hydroptilinae and Stactobiinae .

Remarks. All efforts to accommodate completely the set of four small adult males in any existing genus failed. Superficially, genitalia of these males resemble those of some stactobiine genera such as Catoxyethira —dorsally they are equipped with a pair of stout black spiny structures—or Pseudoxyethira which shares the general appearance of abdominal segments VIII and IX. In superficial appearance, the male genitalia closely resemble those of Catoxyethira pinheyi Kimmins 1958 from Zimbabwe (which is probably a species of Pseudoxyethira ). However, the dorsal spines are unlike any seen in species of Catoxyethira: They are divided into two clearly distinct parts, the distalmost jet black and more slender than the paler proximal part.

Among 6 females collected with 3 of the males, was the very distinctive specimen, illustrated in Figures 35 and 36. We associate this female, tentatively, with the males of Aenigmatrichia asymmetrica which also exhibit unusual modifications.

Possible assignment of this new species to Ithytrichia , subfamily Orthotriichinae , immatures of which are known from Sub-Saharan Africa fail, although again genitalic features of males of both genera are somewhat similar superficially, especially in the form of the phallus which resembles that of most species of Orthotrichia ; however, the head and thoracic features differ significantly. Within the subfamily Hydroptilinae , the combination of features in Aenigmatrichia is distinct from all known Hydroptilinae genera. Thus, we reluctantly erect another monotypic genus among Sub-Saharan Hydroptilidae .