Mortoniella bilineata, Ulmer, 1906

Blahnik, Roger J. & Holzenthal, Ralph W., 2011, Revision of the austral South American species of Mortoniella (Trichoptera: Glossosomatidae: Protoptilinae) 2851, Zootaxa 2851 (1), pp. 1-75 : 61-63

M. bilineata species group

The primary character used to distinguish this group, formerly representing Mortoniella s.s., is the presence of 3 forks in the hind wing (forks II, III and V present), as opposed to only 1 or 2 forks present in species historically placed in Mexitrichia (fork II or forks II and III present). As pointed out by Blahnik & Holzenthal (2008), the character defining the M. bilineata species group is likely a plesiomorphic character. Other characters discussed by Blahnik & Holzenthal (2008), including the presence of a narrow, posteriorly directed ventral process of sternum VI (in both males and females), segment IX of the male with the anteroventral margin produced and with the lobes widely separated dorsally, and the presence of a deeply invaginated tergum VIII in females, are not unique to the M. bilineata group. However, the structure of tergum VIII of females is distinctive for the group and could probably be considered diagnostic. An illustration of the female genitalia for M. bilineata is provided in Fig. 33 , since no female of the M. bilineata species group has been previously illustrated. Its general characters are representative of the group (for those species that have been examined), except for the recurved anterior margin of tergum IX, which is a character attribute peculiar to M. bilineata . A larval character listed by Flint (1963) as diagnostic for the M. bilineata species group, a thickened seta at the base of the foretarsal claw, is difficult to apply in placing species, since very few larvae have been associated or described for Mortoniella . Flint (1963) listed several gestalt characters uniting the taxa placed in the M. bilineata species group, including the tendency of tergum X to be elongate, and several other genitalic characters, not all of which seem to be consistent for the entire group.

Sykora (1999) divided the known taxa into 5 "tentative" subgroups (the M. argentinica , bilineata , enchrysa , flinti , and wygodzinskii subgroups), and also suggested that concepts of relationships are likely to change once the taxa are better known. About 1/2 of these species were placed in his M. bilineata subgroup. Although the included taxa were listed for each group, the defining characters for the subgroups were not discussed. An examination of illustrations for the species and representative specimens from the subgroups, suggests that the majority of species in the M. bilineata species group do have a very coherent "gestalt" similarity, although individual species may vary somewhat from this idealized form. These characters apply especially to the M. bilineata , enchrysa , and wygodzinskii subgroups of Sykora (including the majority of species), all of which have a very consistent morphological pattern. The illustration of M. wygodzinskii ( Fig. 34 ) can be used to point out the characters uniting this group. Character similarities include the following: A more or less elongate tergum X (as suggested by Flint), usually with the mesal margin characteristically notched (as in Fig. 34B ), although sometimes more deeply divided; the presence of sclerotized and setose ventral lobes on tergum X, bordering the dorsal phallic spine; an angulate ventral margin of the dorsal phallic spine, articulating with a sclerotized process on the phallicata [the process usually without dorsolateral processes acting as guides for the paramere appendages ( M. roldani Flint an exception)]; a dorsal phallic spine that is sharply upturned apically and also has it apex rounded, as viewed laterally; a characteristic shape of segment IX, with the anteroventral margin produced and with the posterior margin distinctly angulate in its dorsal 1/2.

Primary differences between the M. bilineata and enchrysa subgroups seem to be based largely on color. A number of the species in the M. bilineata subgroup of Sykora have the forewing distinctively marked with 2 wing bars, 1 at the anastamosis, as is common in Mortoniella , and another more proximal band (a unique character within Mortoniella ). This contrasts with the distinctive color of the M. enchrysa group, with males uniformly golden in color (another unique character within Mortoniella ), without any apparent wing bands, and with the membrane of the wing, beneath the golden setae, darkened or fuscous. Several of the species in the M. bilineata subgroup were described from pharate pupae or from alcohol, making it difficult to determine the original color of the wings, including M. angulata Flint , M. apiculata Flint , and M. hodgesi Flint. Species with 2 wing bands include M. bilineata Ulmer , M. roldani Flint , M. similis Sykora , M. chicana Sykora , and M. iridescens Flint , the first 3 with dark wings and white bands, M. chicana with light brown wings and white bands, and M. iridescens with dark wings and iridescent bands, only visible at some light angles. The only species placed in the M. enchrysa subgroup are M. enchrysa and M. paraenchrysa , although Flint (1996) recorded 2 additional undescribed species from Peru. Based on color considerations, and also genitalic characters, M. denticulata Sykora , which Sykora placed in his M. flinti subgroup, should probably be moved to the M. enchrysa subgroup. Males are nearly golden in color, without wing bars, and females have an indistinct or incomplete wing bar at the usual position, indicating the probable ancestral state for the group. Similarly, M. paralineata , which Sykora described in the M. bilineata subgroup, is described as being yellow with a fuscous wing membrane, suggesting its probable placement in the M. enchrysa subgroup. Mortoniella squamata Sykora, 1999 , which Sykora placed in the M. bilineata subgroup, is described as being golden beige and unmarked, or not strictly conforming to either species group based on color considerations. Similarly, Mortoniella foersteri (Schmid, 1964) is discussed as being dark with a single white wing band. Although the M. enchrysa subgroup seems to represent a monophyletic assemblage, based on color considerations, monophyly of the entire M. bilineata group needs to be more clearly demonstrated.

The M. flinti group of Sykora, as originally conceived, is quite heterogeneous and species differ significantly from the 3 species subgroups discussed above. With M. denticulata removed, only 4 species remain. We have not directly examined any of these species, although we have examined specimens of a species from Venezuela that is apparently very closely related to M. bifurcata Sykora , or possibly conspecific. It differs from the species discussed above in lacking an angulate ventral margin of the dorsal phallic spine and also a somewhat different overall structure of the dorsal phallic spine, as well as lacking an angulate posterior margin to segment IX. In most other respects, however, including the general structure of tergum X and also female genitalia with a deeply incised tergum VIII, it is characteristic of the M. bilineata species group. We believe that it is correctly placed here and that this will also prove to be true for M. flinti Sykora and M. quinas Harper & Turcotte. Based on genitalic considerations, we suspect that M. santiaga Sykora may not only not be a member of the M. flinti subgroup, but may be misplaced in the M. bilineata species group. However, this needs to be confirmed. Mortoniella wygodzinskii , the only species placed by Sykora in his M. wygodzinskii group, is discussed below in the redescription of that species. Morphologically it is very similar to the M. bilineata and enchrysa subgroups, but lacks the distinctive color attributes of either subgroup and has some peculiar morphological distinctions of its own.

Based on genitalic considerations, M. argentinica , type species of the M. argentinica subgroup of Sykora, is being removed from the M. bilineata species group, as discussed in the species description for that species in the section on 'species unplaced to species group'. Both the overall form of the male genitalia, and also that of the female, more closely resemble species in the M. leroda species group. The only other species "speculatively" placed in the M. argentinica subgroup by Sykora is M. unilineata Sykora , which we believe may also be misplaced in the M. bilineata species group. However, this also needs verification. It appears that these species may have been placed in the M. bilineata group based mainly on venational considerations, which as discussed above, may be plesiomorphic.

Figures

FIGURE 33. Mortoniella bilineata Ulmer, female genitalia: A—lateral; B—ventral; C—dorsal: D— glands of terga VI and VII, dorsal.

FIGURE 34. Mortoniella wygodzinskii (Schmid), male genitalia: A—lateral; B—segment IX and tergum X, dorsal; C—phallic ensemble, ventral.