Type species: Mortoniella bilineata Ulmer, 1906.

As a subgenus, distinct from the newly recognized subgenus Nanotrichia, this taxon is restricted to include taxa formerly referred to as members of the bilineata and leroda species groups (Blahnik and Holzenthal 2008, 2011), as well as all of the taxa previously unplaced to species group, except for M. rodmani Blahnik and Holzenthal, 2008. A formal assignment of all species in the genus to subgenus and species group, including those described in this paper, can be found in Table 1. A generic synonymy for the genus as wholde and a more complete listing of literature citations and distributional records for the individual species can be found in the Catalog of Neotropical Trichoptera (Holzenthal and Calor 2017). We have continued to designate species of M. (Mortoniella) within the two recognized species groups (the bilineata and leroda groups), since they are diagnostically distinct and represent about 85% of the species. A third group of species is also considered under the category of “unplaced species,” but is probably not a natural group. It includes species retaining some plesiomorphic characters, but lacking the apomorphic characters used to define either the bilineata or leroda species groups. The individual species may either be basal to one or the other of these two species groups, or basal to both groups combined. Characters suggestive of their phylogenetic placement are discussed under the subgroup headings or species descriptions and in the accompanying phylogeny.

The subgenus Mortoniella can be recognized by a combination of characters. About 75% of the species have more than 1 fork in the hind wing (forks III and/or fork V present, in addition to fork II). Species with the hind wing venation reduced to fork II, as in M. (Nanotrichia), typically have the costal margin of the hind wing more abruptly angulate (Fig. 101B). These species belong to the leroda group and are also characterized by a relatively short ventral process on segment VI and males with the anterior margin of segment IX broadly rounded (diagnostic characters of the leroda group). Hind wing configuration for other species in the subgenus Mortoniella includes having forks II, III, and V present (present in most species of the bilineata group, as well as in the species unplaced to species group) (Fig. 97B, 99B); forks II and III present (various species subgroups of the leroda group) (Fig. 100B); or forks II and V present (the flinti subgroup of the bilineata group) (Fig. 98B). Overall character similarities are difficult to define, due to the variability in genitalia, but there is a tendency for tergum X of males to have the apicolateral lobes distinctly sclerotized and defined, whereas tergum X in members of M. (Nanotrichia) usually have the apicolateral lobes broadly rounded or simple in form.