Metallactus generosus, Suffrian, 1866

Sassi, Davide, 2020, Revision of the Metallactus generosus species-group with a preliminary evaluation of the effectiveness of the endophallus morphology in distinguishing critical sibling species (Coleoptera: Chrysomelidae: Cryptocephalinae), Zootaxa 4877 (1), pp. 148-162 : 151

Key to species of the M. generosus species-group

1 Dark colour of pronotum more extensive, forming a large single mark, anteriorly expanded and including anterior half of lateral margins ( Fig. 1 a–b). Dorsal light colour including, in addition to elytral apical spot, a single generally semicircular patch spreading over posterolateral region of pronotum and anterolateral region of elytron. Frontal yellow spot small, with rounded lateral edges, generally not wider than 0.5 mm ( Fig. 4a ). Pronotal sides slightly more convergent anterad, maximum width near posterior angles. Branches of endophallic sclerite IV distinctly arched dorsally, remarkably expanded apically to form a sickleshaped structure ( Fig. 1f )......................................................... M. generosus Suffrian, 1866

- Dark colour of pronotum less extensive, generally formed by two distinct longitudinal stripes, sometimes coalescing anteriorly but never reaching lateral margins of pronotum. Pronotal sides more regularly arched, maximum width close to midline. Branches of endophallic sclerite IV distinctly to slightly broadened at apex....................................... 2

2 Black elytral colouration formed by a median stripe generally enlarged in posterior half to reach the lateral margin, so that a distinct subcircular or subelliptic yellow spot is present on apical region ( Fig. 2 a–b). Frontal yellow spot broader, with pointed lateral edges and clearly concave sides, generally between 0.7 and 1.2 mm wide ( Fig. 4b ). Branches of endophallic sclerite IV only moderately broadened distally ( Fig. 2f )........................................ M. argentinensis Jacoby, 1907

- Median elytral black stripe usually not widened in posterior half, and in any case not reaching lateral margin, so that light colour forms a continuous stripe along lateral region of the elytra from base to apex ( Fig. 3 a–b). Frontal yellow spot narrower, more irregularly shaped, generally not exceeding 0.6 mm width ( Fig. 4c ). Branches of endophallic sclerite IV distinctly arched towards dorsal direction, remarkably expanded apically to form a sickle-shaped structure ( Fig. 3f ).................................................................................................. M. nigroplagiatus new species

Figures

FIGURE 3. M. nigroplagiatus new species: a–b: habitus (lectotype, from type locality); c–e: median lobe of aedeagus in ventral (c), dorsal (d) and lateral (e) view [0.7 mm]; f: sclerites of endophallus in lateral view [0.5 mm]; g: spermatheca [0.4 mm]; h: antenna [1.6 mm]. scI–IV: sclerites I–IV of endophallus; ds: dorsal spicule. Square brackets: length of scale segment.

FIGURE 4. Frontal view. Metallactus generosus Suffrian, 1866 (a); M. argentinensis Jacoby, 1907 (b); M. nigroplagiatus new species (c).

FIGURES 1–2. Metallactus generosus Suffrian, 1866 (1), M. argentinensis Jacoby, 1907 (2): 1a–b: habitus; 1c–e: median lobe of aedeagus in ventral (c), dorsal (d) and lateral (e) view [0.8 mm]; 1f: sclerites of endophallus in lateral view [0.4 mm]; 1g: spermatheca [0.6 mm]; 1h: antenna [1.6 mm]. 2a–b: habitus; 2c–e: median lobe of aedeagus in ventral (c), dorsal (d) and lateral (e) view [0.8 mm]; 2f: sclerites of endophallus in lateral view [0.5 mm]; 2g: spermatheca [0.4 mm]; 2h: antenna [1.5 mm]. 1a–b: lectotype; 2a–b: lectotype. scI–IV: sclerites I–IV of endophallus; ds: dorsal spicule; sd: setose depression. Square brackets: length of scale segment.