Robertson, Desiree R. & Holzenthal, Ralph W., 2005, The Neotropical caddisfly genus To l h u a c a (Trichoptera: Glossosomatidae), Zootaxa 1063, pp. 53-68 : 55-56

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Position of Tolhuaca within the subfamily Protoptilinae

Schmid (1964) originally placed Tolhuaca in the family Sericostomatidae , commenting on the similarity of the bifid tergum X of the male genitalia to that of Brachycentridae , at that time a subfamily within Sericostomatidae . Flint (1967) later transferred Tolhuaca to Protoptilinae upon discovery that the wing figures in the original description were mislabelled with those of Austrocentrus griseus Schmid 1964 ( Helicophidae ). Since that time, there has been nothing published regarding the placement of Tolhuaca in relation to the other protoptiline genera.

When Schmid (1964) first described the genus he wrote, “Dans l’état actuel de nos connaissances, il est impossible d’assigner une position phylétique au genre Tolhuaca , dont la nervulation assez complète, surtout aux ailes antérieures, contraste avec l’extrême simplification et spécialisation des génitalia…” [“In the current state of our knowledge, it is impossible to assign a phyletic position to the genus Tolhuaca , whose rather complete venation, especially in the forewings, contrasts with the extreme simplification and specialization of the genitalia…” Translation from Schmid (1964)]. The male genitalia ( Figs. 5 View FIGURE 5 A, 7 A) have completely lost both the inferior and preanal appendages, and sternum IX has been reduced to nothing more than a thin, ventral strap. The phallic apparatus ( Figs. 5 View FIGURE 5 A, 5 D, 5 F, 7 A, 7 D) consists of a greatly enlarged, but simple tubular phallobase, and an eversible membranous endotheca. These apparently derived conditions of the male genitalia contrast with other features that imply a basal placement of Tolhuaca within Protoptilinae .

Published works regarding protoptiline phylogeny are few and far between. Morse and Yang (1993) discussed some genera from the East Palaearctic and Oriental regions, and also provided a very useful table comparing wing venation among 15 recognized genera. Ross (1956) provided an early discussion of possible phylogenetic relationships among protoptiline genera and considered the genus Matrioptila Ross 1956 to be most primitive based on characteristics of the male genitalia and wing venation. In Matrioptila , segment IX is complete and ringlike, tergum X consists of a pair of simple lobes, and inferior appendages are present. Forewing veins Cu 1 and Cu 2 are often fused in Protoptilinae , but in Matrioptila , they are separate and distinct along their entire lengths and in the hind wing, Cu 1 is branched. These genitalic and venational characters are primitive according to Ross (1956). Kimmins (1964) described a new genus, Nepaloptila , from Nepal and placed it in Protoptilinae . The genus shares some characteristics of the male genitalia with Matrioptila , but Kimmins (1964) considered Nepaloptila to be more primitive, based on its retention of apical fork V in the forewing, which is usually absent in other Protoptilinae . The venation of Tolhuaca ( Figs. 3, 4 View FIGURE 4 ) is quite similar to that of Nepaloptila ( Kimmins 1964) , differing only slightly. In Tolhuaca, Sc is distinct from R 1 in the forewing, whereas in Nepaloptila, Sc and R 1 are fused near the wing margin. The 2 genera also differ in the position of crossveins in the forewing: those of Tolhuaca form a relatively straight transverse cord along the anastomosis whereas in Nepaloptila , they do not. In the hind wing, A 2 is present in Tolhuaca , but absent in Nepaloptila .

Although Tolhuaca would seem to have more specialized male genitalia than Nepaloptila and Matrioptila , other characters suggest Tolhuaca is the more primitive genus. In Nepaloptila and Matrioptila , the foretibial spur has been lost, whereas in Tolhuaca , although reduced considerably, the spur is retained (Fig. 2). The genus Tolhuaca also has two small setal warts on the mesoscutellum ( Fig. 1 View FIGURE 1 ), which Ross (1956) considered to be primitive; these warts are absent in all other known protoptilines. The female genitalia ( Figs. 6 View FIGURE 6 , 8 View FIGURE 8 ) consist of an elongate oviscapt and 2 pairs of long, rod­like apodemes on segments VIII and IX. The presence of these apodemes is pleisiomorphic within Amphiesmenoptera ( Kristensen 1984). The retention of the foretibial spur, presence of mesoscutellar setal warts, and the structure of the female genitalia suggest that Tolhuaca deserves a basal placement within the subfamily Protoptilinae .