Mecosarthron tritomegas Lameere, 1920

Santos-Silva, Antonio & Lingafelter, Steven W., 2012, Morphological Analysis Of Mecosarthron Buquet And Xixuthrus Thomson And Reevaluation Of Generic Assignment Of Xixuthrus Domingoensis Fisher (Coleoptera, Cerambycidae, Prioninae), Papéis Avulsos de Zoologia 52 (27), pp. 315-332 : 328-331

Mecosarthron tritomegas Lameere, 1920

( Fig. 7 )

Mecosarthron tritomegas Lameere, 1920: 137 ; Blackwelder, 1946: 552 (checklist); Damoiseau & Cools, 1987: 38 (type); Monné & Giesbert, 1994: 5 (checklist); Monné, 1995: 7 (cat.); Monné & Hovore, 2005: 14 (checklist); 2006: 13 (checklist); Monné, 2006: 54 (cat.).

Remarks: Mecosarthron tritomegas was described from Brazil, without any detailed locality: “Un male du Brésil (par Boneuil)”. The photo ( Fig. 7 ) sent by Noël Mal ( IRSN) confirms that information, but the collector’s name is Bonneuil, and the specimen is from the Desbrocher Collection.

Cambefort (2007) wrote on comte Roger Bonneuil: “Grand amateur de coléoptères, membre de la SEF (1858, démission em 1875), le comte de Bonneuil put réunir une riche collection en effectuant de nombreux échanges et achats. Il acquit notamment la collection Monchcourt*. De sa prope collection, dispersée après 1900, les groupes suivants parvinrent au Muséum: buprestides via Théry*; curculionides via Clerc*; malacodermes, clérides et phytophages via Pic*”. In the collection Monchcourt, for example, there was part of the collections of Castelnau, Guérin- Méneville, etc. Thus, it is impossible to track the origin of the holotype of M. tritomegas .

Although we do not know the exact locality where the specimen was collected in Brazil, it is likely that it is from Central Brazil, because Franceschini (2002) recorded a female of Appula sericatula Gounelle, 1909 from IRSN collected by Bonneuil in Goiás.

According to Lameere (1920), M. tritomegas closely resembles M. buphagus , but has very different antennae, more similar to those of Ialyssus Thomson, 1864 (the scape is proportionally shorter, weakly surpassing the posterior edge of eyes and antennomere III is longer than the scape, twice as long as antennomere IV, and about as long as IV-V together). In our examination, the form of the scape is more similar to males of Ialyssus tuberculatus (Olivier) than to males of M. buphagus . However, many species of Macrotomini have the scape somewhat similar to M. tritomegas , while M. buphagus has an unusual scape. That character alone suggests that M. tritomegas is not a true Mecosarthron , however, another character, not mentioned by Lameere, is the form of the tibiae: In M. tritomegas , the form of the foretibiae is not similar to that of the meso- and metatibiae, and it is identical to that in Xixuthrus . This is strange because that strong difference (shape and length) among the tibiae does not occur in M. buphagus and M. gounellei in which the protibiae are little differentiated.

Lameere (1920) suggested that M. tritomegas is intermediate between M. gounellei and M. buphagus . However, M. tritomegas has no characters linking M. gounellei and M. buphagus . Comparing the scape in males of M. gounellei with males of M. buphagus , it is possible to see that they have some similarities in shape (e.g., form, basal curvature), although it is smaller and not ventrally rough. In M. tritomegas the scape is less uniformly enlarged from base to apex and also less curved at the base. Mecosarthron tritomegas is not intermediate between the other species of the genus because the scape is smaller than in the others. Antennomere III in males of M. gounellei and M. buphagus are very similar in size and equal to or just longer than IV, while in M. tritomegas antennomere III is distinctly longer, about twice the length of IV. Thus, using this feature, M. tritomegas is not intermediate between M. buphagus and M. gounellei . Last, the foretibiae in males of M. gounellei and M. buphagus are very similar (size, shape, and similarity with the other tibiae), while in M. tritomegas they are strongly different.

Lameere (1920) states further, on Ialyssus : “son existence [ M. tritomegas ] rend précaire le maintien du genre Jalyssus [sic] que ne diffère de Mecosarthron que para l’absence de pubescence et la présence d’une ponctuation sexuelle sur le prothorax du mâle”. However, the pronotum in males of Ialyssus tuberculatus , which is distinctly different from that in Mecosarthron due to the distinct microsculpture, is not the only difference between Mecosarthron and Ialyssus : In Ialyssus the mandibles and tarsi are shorter (mainly tarsomere V), and the pubescence of the elytra is inconspicuous. Melzer (1919), who agreed with nearly all of Lameere’s proposals in his “sous-groupes”, and considered them as tribes, wrote: “O habito do Julyssus [sic] effectivamente é bastante semelhante ao Mecosarthron , mas embora seja sua lingueta bilobada, a grande difference sexual entre ♂ e ♀ do Jalyssus [sic] demonstram, que o mesmo não deve ser relacionado com aquelle gênero”, commenting that Ialyssus is very similar to Mecosarthron , but the strongly sexually dimorphic conditions suggests that it cannot be closely related to that genus.

Upon examination of the photos of the holotype of M. tritomegas sent by Noël Mal ( IRSN), we note that apparently the prothorax + head were glued to the mesothorax, and that the elytra were pubescent. Mal (pers. comm.) confirmed, “there is a tiny +/– dense pilosity quite apparent under enlargement but reduced on front of elytra (erosion?). The pronotum pubescence is longer but not so dense”. Based on the photos and information sent by Noël Mal we think the possibility exists that the holotype is a composite specimen comprised of the body of a male of M. buphagus and head and prothorax of another species. The strong difference between the protibiae and meso- and metatibia, also corroborate the hypothesis of a composite specimen. However, we recognize the possibility that it is an unusual species, known only from the holotype, or an incorrectly labeled specimen originating from elsewhere in the world, because, for example, in Xixuthrus there is this kind of differentiation among the tibiae. We searched for specimens that match M. tritomegas in the largest entomological collections in Brazil ( DZUP, INPA, MCNZ, MNRJ, MZSP) and in the USNM, but without success.

Figures

FIGURE 7: Mecosarthron tritomegas Lameere, holotype (male). A. dorsal habitus; B. ventral habitus; C. holotype labels.