Metacyclini Chapuis, 1875

Subtribe Metacyclini Chapuis, 1875

Seven genera from this tribe were studied from the Neotropical region. The median lobes of all studied males had elongate lateral endophallic sclerites that, when pushed out through the orifice, rotated either to a perpendicular position relative to the rest of the aedeagus, or rotated backward almost a full 180° with the former apical part now facing toward the base of the median lobe. Byblitea jansoni (Baly, 1864) demonstrates the latter case ( Fig. 3D, E View FIG ). The narrow lateral sclerite in the everted position has a row of small hooked teeth on its apex ( Fig. 3E View FIG ), now facing the basal part of the median lobe. The apex of the endophallus bears a complex sclerotized structure that includes a needle-like central spine and a lateral spine with a crochet-hook tip ( Fig. 3D View FIG ). The bursa of the female ( Fig. 3F View FIG ) shows an area with apparent abrasion scars.

An unidentified species of Chthoneis Baly, 1864 (sp. 1) had two backward-facing rotating sclerites with a sharp tooth on the median lobe: they are shown ( Fig. 3G View FIG ) in the process of being everted, and are fully extended in Figure 3H View FIG . An associated female ( Fig. 3I View FIG ) had a pair of possible puncture marks at a corresponding site, near the basal end of the bursa, but no other evidence of genital damage. A second undescribed species of Chthoneis (sp. 2) ( Fig. 3J View FIG ) differed in detail from Chthoneis sp. 1 in having a single sharp tooth, but both species show two reversing lateral sclerites, and a short endophallus bearing a relatively large complex apical sclerite. In the case of Chthoneis sp. 2 , the everted endophallus did not align along the axis of the median lobe, but this may be an artifact of preparation. A single female of this species had no convincing evidence of bursal damage.

An undescribed Costa Rican Masurius Jacoby, 1888 ( Fig. 4A View FIG ) displayed a complex endophallus displaying sclerites in the form of recurved spikes, a row of long spines, an elongate hook, and an elongate apical sclerite. Despite the impressive armature of the males, a female with a spermatophore collected along with the males had only a few possible scars ( Fig. 4B View FIG ). A second female that lacked a spermatophore had no signs of punctures in the bursa.

Endophalli of Exora encaustica (Germar, 1823) ( Fig. 4C View FIG ), Hecataeus Jacoby, 1888 species ( Fig. 4D View FIG ), and Malacorhinus Jacoby, 1887 species ( Fig. 4F View FIG ) all have lateral sclerites that lack sharp points (although apical sclerite complexes have them) but deploy at various angles to the main axis of the endophallus. The lateral sclerites of Exora Chevrolat, 1837 and Malacorhinus rotate to right angles to the endophallus, whereas in Hecataeus ( Fig. 4D View FIG ) the sclerite rotated a full 180°. The female of Hecataeus ( Fig. 4E View FIG ) shows a possible puncture scar, whereas the females of Malacorhinus ( Fig. 4G View FIG ) and Exora (not shown) do not show signs of puncture or other tissue damage. The female of Malacorhinus sp. has a pair of large branched sclerites on the inner surface of the bursa ( Fig. 4G View FIG ); the female of Exora has a similar arrangement of bursal sclerites.

There is a pair of curved spurs at the base of the median lobe in males of the Galerucina and Metacyclina (as in Figs 2A View FIG , C-E; 3A, D, G, H, J; 4A, C, F). This is an important taxonomic character that distinguishes Galerucina and Metacyclina from the remainder of the Galerucini ( Viswajyothi & Clark 2022) but is also found elsewhere in the Chrysomelidae (e.g. Eumolpinae ; Flowers 1999); these spurs are not known to actively participate in copulation.