Meleoma, Fitch, 1855

Tauber, Catherine A., 2019, A new species of Ungla (Neuroptera: Chrysopidae) that exhibits remarkable homoplasy in male secondary sexual characters, Zootaxa 4700 (1), pp. 87-101 : 97-100

Homoplasy with Meleoma Species

As shown above, U. pseudomeleoma ’s secondary sexual characters are highly modified and very unusual for the genus Ungla . However, they also appear highly modified even when compared with those of Meleoma , a genus noted for elaborate expressions of the antennae, vertex, and frons. Indeed, U. pseudomeleoma ’s features appear to mimic those of Meleoma species in many ways.

Antennal modifications. The elongation of the male U. pseudomeleoma scape and the enlargement and setation of its basal flagellar segments ( Fig. 8A ) closely resemble those of several Meleoma species, specifically Meleoma emuncta (Fitch) ( Fig. 8B ); for comparison with a simpler male scape in Meleoma , see Meleoma undescribed sp. #1 ( Fig. 8C ), and for a more complex male scape see Meleoma stangei Penny ( Fig. 8D ). Interestingly, in all the sexually dimorphic species (the Meleoma species, including the elaborate M. stangei , and also U. pseudomeleoma ), the pedicel does not appear to be modified significantly. The elaborate features are limited to the scape and flagellum. The main antennal differences between U. pseudomeleoma and the majority of the horned Meleoma species are in the orientation and insertion of the scapes. In most Meleoma species the bases of the scapes are widely separated (usually by more than the width of the scape itself), and they extend outward laterally from the base. In U. pseudomeleoma the scapes originate close to each other, and they extend in a forward direction. However, U. pseudomeleoma falls within the range of variation expressed by Meleoma . For example, in the undescribed Meleoma sp #1, the interantennal horn is reduced or absent, and like those in U. pseudomeleoma , the scapes of males and females originate close to each other and generally extend in a forward direction ( Figs 8C , 10F ).

Interantennal horn (upper horn). The interantennal horn of U. pseudomeleoma resembles, and yet differs, from that of most species in the M. emuncta and M. dolicharthra (Navás) groups of Meleoma (compare Fig. 9.A 1 with Figs 9B, 9C, and 9D ). For example, in almost all of the horned Meleoma species, the base of the interantennal horn is located on the dorsal surface of the vertex between the dorsal toruli. And, in most of the horned Meleoma species, the dorsal interantennal region is relatively broad and smooth ( Figs 9B, 9C ); in others it can be furrowed, or the horn may be small ( Fig. 9D ). When a horn is present, the distal end usually has a deep or shallow bifurcation or other modification; often the paired tips are rounded and setose. The interantennal horn of U. pseudomeleoma is within the range of variation expressed by species of Meleoma ; its horn is longitudinally furrowed from its base; the furrowing persists distally; and the tip of the horn is bifurcated and carries small setae. However, unlike in Meleoma species the furrowed base of the interantennal horn bends ventrally between the scapes and onto the upper surface of the frons; it then bends at a right angle to extend forward at a lower level on the frons ( Fig. 9.A 1-3 , 10A, 10B ). Also, the bifurcated arms of the horn are somewhat flattened vertically ( Fig. 10B ), not rounded or flattened horizontally as in most or perhaps all Meleoma species.

Frontal cavity. The frontal cavity of U. pseudomeleoma is somewhat similar in shape to that of species in the M. dolicarthra species group; its lateral margins are rounded, emarginate, and fairly distinct. It is slightly shallower than the cavities of most Meleoma species. It is noteworthy that U. pseudomeleoma appears to lack a frontal horn extending from within the cavity (below the interantennal horn), as occurs in many but perhaps not all horned species of Meleoma (For examples, see Figs 10 C–F).

In most, if not all, horned Meleoma species, the lower surface of the frontal cavity and/or the posterior surface of the clypeus are very setose and apparently glandular. Also, in some Meleoma species, e.g., Meleoma hageni Banks , there is a horn-like structure at the distal end of the cavity. Such is also the case with U. pseudomeleoma . It has a tall, narrow ridge along the distal margin of the frontal cavity, and the upper edge of the ridge bears a pair of brownish, triangular, vertically striated projections that give off a shiny metallic sheen under some lighting conditions. These structures appear to be formed by a series of rigid, closely spaced setae extending upward. Superficially, the structures in U. pseudomeleoma appear homologous to similar-looking ones in M. hageni ( Fig. 10C ) and Meleoma signoretti Fitch ( Tauber 1969, Plate 5C), which also are on raised areas below the frontal cavity and are comprised of tufts of setae with a metallic sheen. However, on the M. hageni male, the ridge and setal tufts may be located on the upper (proximal) end of the clypeus, not on the distal end of the frons as in U. pseudomeleoma and M. signoretti . Thus, homology of these structures awaits confirmation. In all of the species mentioned above, and in at least some other Meleoma species, the clypeus appears to be enlarged, rigid, and shield-like. The clypeus of U. pseudomeleoma may have similar but less pronounced enlargement.

Function of the male head modifications. The sexually dimorphic structures of the head were shown to have roles in courtship and mating for at least two species of Meleoma ( Toschi 1965, Tauber 1969). Specifically, during courtship the female approaches the male frontally and inserts her mouthparts into his frontal cavity. She appears to feed at the frontal region while he initiates copulation, and in M. emuncta it appears that the enlarged and curved male antennal structures hold the female in place while he establishes the copulatory connection. It would be very interesting to determine if the homoplasy in the sexually dimorphic head morphology seen in the horned Meleoma species and U. pseudomeleoma also includes homoplasy in behavioral function during courtship and copulation.

Figures

FIGURE 1. Ungla pseudomeleoma, sp. nov., Holotype (male, Peru: La Libertad, FSCA). A. Head, prothorax (frontolateral); B. Head, prothorax (lateral); C. Head (frontal); D. Head (lateral); E. Face (frontal); F. Head, prothorax (dorsal). f1, first flagellomere; in.fu., interantennal furrow; in.h., interantennal horn; lo.h., lower horn; ped, pedicel.

FIGURE 8. Similarity in the antennal features of Ungla pseudomeleoma with those of three species of Meleoma. A. Ungla pseudomeleoma, sp. nov., Holotype (Peru: La Libertad, FSCA); B. Meleoma emuncta Fitch (USA: California, TRC); C. Meleoma undescribed sp. #1 (USA:Arizona, TRC); D. Meleoma stangei Penny (Mexico: Baja California, San Diego County Museum of Natural History). f1, first flagellomere; h, horn extending from scape; ped, pedicel; sc, scape.

FIGURE 9. Comparison of the male cranial features of Ungla pseudomeleoma with those of selected Meleoma species, A. Ungla pseudomeleoma, sp. nov., Holotype (Peru: La Libertad, FSCA). A1. Dorsal aspect (base) of interantennal horn (arrow indicates dorsal origin of mesal trough), A2. Frontolateral aspect of interantennal and lower horns (The arrows indicate paired distal arms of the interantennal horn; the lower horns are brown, triangular, below and anterior to the interantennal horns), A3. Frontal close-up of interantennal trough, interantennal horn, and lower horn (upper arrows indicate tips of paired interantennal horns; lower arrows indicate paired lower horns); B-D. Dorsal aspect of interantennal horn (lower arrows on each figure indicate base of the horn; upper arrows indicate tip of interantennal horn. B. Meleoma emuncta Fitch (USA: California, TRC); C. Meleoma hageni Banks (USA: Arizona, TRC); D. Meleoma unidentified sp. (Argentina: Jujuy, TRC).

FIGURE 10. Male cranial features of Ungla pseudomeleoma and selected Meleoma species. A, B Ungla pseudomeleoma, sp. nov., Holotype (Peru: La Libertad, FSCA). A. Lateral; B. Frontolateral (arrows in both A and B indicate paired arms of the interantennal and lower horns); C. Meleoma hageni Banks (USA: Arizona, TRC), lateral (downward-facing arrows indicate interantennal and lower horns, upward-facing arrow indicates horn within frontal cavity); D. Meleoma furcata (Banks) (USA: Arizona, TRC), lateral (arrow indicates horn within frontal cavity); E. Meleoma stangei Penny (Mexico: Baja California, San Diego County Museum of Natural History), lateral (arrow indicates double horn within frontal cavity); F. Meleoma undescribed sp. #1 (USA: Arizona, TRC), frontolateral (arrow indicates horn within frontal cavity; note absence of interantennal and lower horns).