Megamerus, Mac Leay, 1827

Sekerka, Lukáš, 2007, On the genus Rhagiosoma and the identity of R. madagascariense (Coleoptera: Chrysomelidae: Sagrinae: Megamerini), Acta Entomologica Musei Nationalis Pragae 47, pp. 195-202 : 196

The genera Megamerus and Rhagiosoma

Externally, Rhagiosoma and Megamerus have a similar shape of body outline and should be distinguished by characters summarized in Table 1.

Megamerus and Rhagiosoma also differ in the shape of male genitalia; this character was not studied by MONRÓS (1956). I have examined male genitalia of type specimens of the following species: R. chapuisi nom. nov., R. fraternum , R. grossum , R. madagascariensis and four other unidentified Madagascan species. I have also seen specimens of Megamerus kingi MacLeay, 1827 (type species of Megamerus ), and M. cf. femoralis Lea, 1917. I found strong differences in the shape of the parameres and aedeagus. In Megamerus , the parameres are robust and gradually thickened towards apex, with a shallow apical cleft and apex of each face broadly rounded ( Fig. 1c ), this structure is rather similar to Sagra Fabricius, 1792 . Rhagiosoma have apices of parameres not thickened but with a very deep apical cleft (often reaching to 2/3 of length) and each apical face angulate to slightly obtuse ( Figs. 2c, 3c ). The aedeagus in Megamerus is very stout, parallel-sided, without a sharp apex and with a shallow apical cleft ( Figs. 1a,b ). On the other hand, Rhagiosoma has the aedeagus parallel-sided in the anterior part and then tapered; the apex is sharp and differently shaped than in Megamerus ( Figs. 2a, 3a ). The findings mentioned above lead me to remove Rhagiosoma from the synonymy of Megamerus .

Figures

Figs. 1-3. 1 – Megamerus kingi MacLeay, 1827; 2 – Rhagiosoma madagascariense (Heyden, 1877); 3 – R. chapuisi nom. nov.; a – aedeagus, dorsal view; b – aedeagus, lateral view; c – parameres, dorsal view.