Megacoelum

Chérot, F. & Malipatil, M. B., 2016, A review of Adelphocoris - Creontiades - Megacoelum complex (Hemiptera: Heteroptera: Miridae: Mirini), with descriptions of two new genera and four new species, Zootaxa 4126 (2), pp. 151-206 : 154-156

Adelphocoris-Creontiades - Megacoelum complex

Hypothetical Creontiades complex sensu Chérot, Yasunaga & Gorczyca 1999: 15 –16 (in part).

Diagnosis. Body elongate, parallel or subparallel-sided, dorsally glabrous or with one or two types of vestiture (one type setae-like or silky, white or yellowish, recumbent, the other setae-like, dark brown to black, erect or suberect); pronotum, scutellum and hemelytra densely or sparsely, narrowly and shallowly punctate to almost impunctate; vertex usually with a longitudinal sulcus, frequently deep and lacking basal carina; antennae long, frequently longer than body, segments thick; diameter of last two antennal segments similar to that of base of second segment; basal diameter of second segment frequently wider than length of pronotal collar; first and second segments sub-cylindrical and generally not club-like, fourth segment very slightly pointed at apex; first metatarsal segment frequently shorter than second; hemelytra slightly to moderately declivous at cuneal fracture; veins generally raised; left paramere with a tertiary lobe; right paramere frequently with a translucent secondary lobe beneath short primary apophysis.

Included genera. Adelphocoridea Poppius, 1912 , Adelphocoris Reuter, 1896 , Adelphocorisella Miyamoto & Yasunaga, 1993 , Carvalhocapsus Chérot & Carpintero, 2006 , Cheilocapsidea Poppius, 1915 , Chimsunchartella Chérot & Pauwels, 2000 , Creontiades Distant, 1883 , Galapagomiris Carvalho in Carvalho & Gagné, 1968 , Gollneria Carvalho, 1983 , Megacoelum Fieber, 1858 , Neomegacoelum Yasunaga, 1998 , Neopeplus Chérot, Malipatil & Schwartz, 2003 , Orientomiris Yasunaga, 1997 , Pleurochilophorus Reuter, 1905 , Poppiocapsidea Yasunaga, 1998 , Poppiomegacoelum n. gen., Pseudomegacoelum n. gen., Tricholygus Poppius, 1910b , Vairocanamiris Yasunaga, 2011, Waucoris Carvalho, 1987 .

Discussion. The generic-level classification of the tribe Mirini remains unclear. Several authors, as detailed below, have mentioned the hypothesis of a close relationship between some of the genera treated in this contribution. Usually they have compared only a limited number of genera in each work, however a critical reading of their papers underlines multiple similarities between a majority of taxa across their works.

As already noted, the genus Creontiades was described by Distant (1883) for the species Megacoelum rubrinerve Stål, 1862 .

Later, Reuter (1905a: 4), in his original description of Pleurochilophorus , briefly compared it with Megacoelum . In his African fauna study, Poppius (1912: 18) compared Pleurochilophorus with both Creontiades and Megacoelum , and Adelphocoridea with Adelphocoris (op. cit.: 47). Linnavuori (1974a: 8) also considered Megacoelum and Pleurochilophorus as closely related, essentially separated by the head structure.

Poppius (1915a: 14) suggested relationships between his new genus Cheilocapsidea —erected to accommodate a species described by Distant (1909) in Megacoelum —and Pleurochilophorus by choosing to compare it only with this last genus and with Cheilocapsus.

Carvalho (1952) synonymized Cheilocapsidea and Tricholygus with Creontiades . Later, he (1983) described Gollneria as a new genus, unfortunately without any comparison with other mirine genera, just stating Gollneria is not a true Megacoelum . Finally, the same author ( Carvalho 1987: 156–157) erected Waucoris to accommodate all species described by Poppius (1915a) under the name Adelphocoris from the Indo-Australian region and compared Waucoris only with Adelphocoris on the basis of not very relevant character states (shape of larger areola of membrane and coloration of tibial spines).

Schmitz (1976: 480), partly based on literature, assumed Adelphocoris , Creontiades and Megacoelum belonged to the same group of impunctate Mirini by their head, antennal and tarsal structures.

Yasunaga (1990a: 607) noted a resemblance between Adelphocoris and Creontiades , but considered these genera, with Adelphocorisella , are more closely related to Phytocoris than to Megacoelum (Yasunaga pers. comm. dated March 0 4th 2015 onwards). In their description of Adelphocorisella, Miyamoto & Yasunaga (1993: 47, 48) compared it only with Adelphocoris .

In the second part of his revision of Japanese Creontiades and allies, Yasunaga (1997b: 729) recognized a close relationship between Megacoelum and Orientomiris . Later, he (1998: 63), noted superficial resemblance of Neomegacoelum with Megacoelum and Orientomiris .

Chérot, Yasunaga & Gorczyca (1999) suggested a hypothetical “ Creontiades complex” within the tribe Mirini to group Creontiades , Megacoelum , Neomegacoelum , Orientomiris and Poppiocapsidea .

Chérot & Pauwels (2000) did not compare Chimsunchartella with all members of the Adelphocoris- Creontiades - Megacoelum complex as defined in the present work, but noted several similarities between Adelphocoris and Chimsunchartella . A hypothetical phyletic relationship between both genera is suggested by Chérot & Malipatil (2003).

Rosenzweig (2001), in his studies on Palearctic Mirini , considered a “ Creontiades complex” including the genera Cheilocapsidea , Creontiades , Megacoelum , Neomegacoelum , Orientomiris , Pleurochilophorus and Poppiocapsidea and an “ Adelphocoris complex” including the single genus Adelphocoris . He noted some resemblance between Adelphocoris and the west-Mediterranean genus Thiomiris Rosenzweig, 1997 — a genus remained unclassified in his system—and placed on the same unranked level as these two complexes, his Closterotomus complex and his Calocoris complex described in more detail in Rosenzweig (1997). The relationships between all these genera, groups or complexes were not tackled in Rosenzweig’s work (op. cit.) and their diagnoses not systematically provided.

In his unpublished preliminary phylogenetic analysis of the genera of the tribe Mirini , Chérot (2002) grouped in two basal clades a majority of the genera of the complex as defined here before. However, the matrix used in this cladistics analysis should be reviewed at light of recent works on the tribe, including the present one.

Carpintero & Chérot (2002: 44–46) compared Carvalhocapsus (under the junior homonym Carvalhocoris) with the members of Creontiades complex sensu Chérot, Yasunaga & Gorczyca, 1999 , also with Adelphocoris , Adelphocoridea , the Mirini with a swollen scutellum (obviously a non-monophyletic convenient group) and Phytocoris .

Chérot, Malipatil & Schwartz (2003) mentioned, in a relatively indistinct way, several similarities that existed between male genitalic structures of Neopeplus , Adelphocoridea and Pleurochilophorus such as paramere shape, endophallic sclerite shape and position etc.

Yasunaga (2011) assumed, without specified explicitly why, Vairocanamiris to be most closely related to Cheilocapsidea and Cheilocapsus Kirkaldy, 1902, the similarities with some other genera of Mirini including Orientomiris being supposed superficial. For us, the similarities between Cheilocapsidea and Cheilocapsus could also be superficial. The genus Cheilocapsus differs from all members of ACMc, including Cheilocapsidea , by the wide, coreid-like, body shape, the tumid frons, the two last antennal segments significantly narrower than the first two, the shagreened pronotal disk and the dorsal pilosity. As suggested by Yasunaga (2011), a relationship between Cheilocapsus and Pantilius, two genera with similar habitus, seems very likely.

The phallic comb of several Phytocoris species seems relatively similar to those observed in Adelphocoris . The comb-shaped almost flat or spoon-like sclerite, with wide and relatively short slightly curved teeth on lateral sides is structurally the same in both genera. In Phytocoris Fallén, 1814 , it was considered by Stonedahl (1988) as the apical part—termed “sclerotized process”—of larger structure subdivided at level of secondary gonopore (the “ACH” sensu Carpintero & Chérot, 2008 ) and may support the phallus in inflation. In Adelphocoris , the combshaped sclerite is basally connected to a spicule-like sclerite, generally absent in Phytocoris .

Presence of phallic comb could reflect relationships between the genera Adelphocoris and Phytocoris (T. Yasunaga pers. comm. dated from March 4th 2015). However, phallic structures of Phytocoris are amazingly variable, the comb being frequently absent. The shape of metafemora of Adelphocorisella and Creontiades could also group both genera with Phytocoris . Nonetheless, all Phytocoris species do not have the same metafemoral shape. Moreover, the width of the last two antennal segments, the structure of the vertex, and the dorsal punctation differ between Phytocoris and the members of our hypothetical ACMc.

On the basis of external morphology, the African genus Megacoelopsis Poppius, 1912 seems closer to Rosenzweig’s Calocoris and Closterotomus complexes than to our Adelphocoris - Creontiades - Megacoelum complex. This would also be the case with the genera Loristes Josifov & Kerzhner, 1972, Thiomiris Rosenzweig, 1997 and Taurocalocoris Carapezza, 1998, as suggested by Rosenzweig (2001). Some other genera of “impunctate” Mirini , such Liocapsus Poppius, 1915, Orientocapsus Yasunaga & Schwartz, 2007 and Philostephanus Distant, 1909 share several character states with ACMc members, but not all, differing particularly by antennal and head structures and by genitalia of both sexes.

To identify which character states are truly homologous or homoplasious and the relationships of these genera with the ACMc members and between them will require a comprehensive cladistics analysis of the tribe at generic level on a world basis. Such analysis would eventually assist in assessing the validity of ACMc of genera as a monophyletic taxon in the tribe Mirini . However we are convinced that a clarification of the definition of each genus is an indispensable prerequisite for such an analysis, even if such analysis could modify the diagnosis and limits of some taxa studied in the present work.