Liogenys Guerin-Meneville , 1831

Cherman, Mariana Alejandra, Mise, Kleber Makoto, Moron †, Miguel Angel, Vaz-de-Mello, Fernando Z. & Almeida, Lucia Massutti de, 2017, A taxonomic revision of Liogenys occurring in Brazil with an interactive key and remarks on New World Diplotaxini (Coleoptera, Melolonthidae), ZooKeys 699, pp. 1-120 : 2-11

Liogenys Guerin-Meneville, 1831

Liogenys Guérin-Méneville, 1831: pl. 3 (orig. desc. [drawing of L. castaneus ]); Guérin-Méneville 1838: 84 (red.); Blanchard 1851: 167 (rev.); Burmeister 1855: 13 (red. and rev.); Lacordaire 1856: 269 (red.); Harold 1869b: 1140 (check.); Dalla Torre 1913: 318 (check.); Blackwelder 1944: 228 (check.); Frey 1969: 38 (key); Evans 2003: 206 (check.); Evans and Smith 2005: 174 (check.); Evans and Smith 2009: 175 (check.); Cherman et al. 2016: 23 (sys.). Type-species. Liogenys castaneus Guérin-Méneville, 1831(monotypy).

Amphicrania Dejean, 1833: 163 (cat.); Burmeister 1855: 13 (syn.). Type-species: Amphicrania palpalis (Eschscholtz, 1822) (monotypy).

Hilarianus Blanchard, 1851: 168 (orig. desc.); Cherman et al. 2016: 23 (syn.) Type-species: Hilarianus anguliceps Blanchard, 1851.

Peritryssus Reitter, 1918: 77 (orig. desc.); Keith and Lacroix 2003: 48 (syn.) Type-species: Peritryssus excisus Reitter, 1918 (monotypy).

Homoliogenys Gutiérrez, 1952: 216 (orig. desc.); Cherman et al. 2016: 23 (syn.) Type-species: Liogenys tarsalis Moser, 1921a (monotypy).

Diagnosis.

Liogenys is distinguished from all other Diplotaxini genera by the following combination of features: frons and clypeus concave in dorsal and lateral view; basal protarsomere (I) shorter than tarsomere II; mesotibial transverse carina/ae provided with spines shorter or equal to those forming the apical crown; metacoxae with bristles or scales, never both at the same time, and pygidium with umbilicate punctures.

Redescription.

Length 6.5-16.3 mm; width: 3.5-8.3 mm. Body sub-parallel, sometimes wider in the posterior half; elytra and body may be unicolored or with different colors, which vary from yellowish, brownish, reddish-brown, purplish-red to black. Head: distance between eyes commonly twice the width of one eye, but occasionally three to five times; frons and clypeus forming together a concavity (Fig. 5); fronto-clypeal suture absent or barely distinguishable (as in L. tarsalis and L. forcipata Frey); fronto-clypeal impressions evident in frontal view (Fig. 4); clypeus anteriorly bent forward and emarginate (Fig. 1), clypeal emargination may be angled, sub-angled or rounded, wide or narrow, mostly forming two tooth-like projections (Figs 17-22); the lateral margin of the clypeus may form a projection, rounded or sharp, in this case it resembles a tooth (Figs 6, 18, 21); clypeus S-shaped in lateral view (Fig. 7); outer margin of the maxillae straight (see Cherman et al. 2016), with four or five teeth at the apex (Figs 25, 27); distal palpomere up to two-fold wider than its apex, sensorial surface generally forming a fovea (except in L. sinuaticeps Moser and L. unicolor Evans) deep or shallow and with variable length (Figs 26, 28); labium trapezoidal with maximum width at the apex (except in L. sinuaticeps ); ligula emarginate anteriorly; mentum excavated on the disc (except in L sinuaticeps , Fig. 24); ligula length shorter than the excavation (Fig. 23); labrum in frontal view convex on upper margin and shorter than the ventral portion of clypeus (Fig. 8); antenna 9- or 10-articulated. Prothorax: pronotum wider medially, forming a lateral convexity more or less pronounced (Figs 1-3); anterior margin of pronotum may be straight or slightly produced medially (Figs 2, 3); sometimes flanged anteriorly (as in L. corumbana Moser and L. fusca ; Fig. 61D, 64D); pronotal posterior corners right or obtuse-angled, rounded or obsolete (corners not distinguishable) (Figs 1-3); prothorax setose posteriorly, covered with short or long bristles (Figs 29-30); proepisternum setose, scaly or bristled, with short and/or long bristles. Pterothorax: Scutellum triangular, ogival, or rounded; normally with punctures grouped at the base and/or at the sides, or sometimes without any pattern (Figs 34-36); metasternum more or less setose laterally; distance between meso- and metacoxae up to twice the length of the metacoxa (except in L. concolor ). Elytra: glabrous or setose; densely and coarsely punctured; elytral suture with non-uniform width; elevated or not, unicolored with the elytron or darker; three or four elytral ridges more or less noticeable, separated from each other by gaps that are twice as wide as one ridge, the first gap equal to or narrower than the second one; subapical callus of elytron closer to the elytral suture than to the external margin (feature of all Neotropical Diplotaxini ; see Cherman et al. 2016). Legs: procoxae setose, bristled and/or scaly (Fig. 9), protibial inner margin concave and the outer one with three teeth perpendicular to the tibial axis (see Cherman et al. 2016), the basal tooth is always the smallest, in males the basal tooth is more reduced and may be absent depending on the species; the two other protibial teeth may be equal in size or not, when different, the apical one is commonly the longest, but in some cases the middle is the longest; protibial disc with two medial longitudinal carinae; protarsi longer than the head; protibial apical spur on inner margin commonly present; protarsal tarsomere I shorter than tarsomere II; basal apophysis of metacoxae produced beyond the outer margin of trochanter (Fig. 32) (except for L. tarsalis , L. sinuaticeps and L. unicolor , Fig. 33); mesotibiae with one or two transverse carinae bearing spines, mesotibial spines equally as long as the spines of the apical crown (Figs 42-45), the apical carina may be complete or incomplete (as described above, in “standards” of morphological study); pair of apical spurs on apex of meso- and metatibia equal to or different in size, in male metatibia the shorter spur varies in shape among the species (Figs 46-47), the gap between spurs is narrower or equal to the base of one spur; tarsi covered ventrally with setose pads; length of basal metatarsomere varies from equal up to one-half the length of the second; all claws bifid and generally symmetrical, they vary in the size of the upper tooth and in the distance between teeth (Figs 39-41). Abdomen: propygidium visible, slightly visible or hidden by the elytra; glabrous or setose, with scales and/or bristles; pygidium convex or flat (Figs 37-38), disc glabrous or setose, throughout the surface or only at apex; punctures, if present, umbilicate (Fig. 31); shape sub-quadrate or sub-trapezoidal (Figs 13-16), twice the length of ventrite V or more; depending on the species, the maximum width either exceeds or does not exceed the width between the propygidial spiracles (Figs 13-14).

Dimorphism.

Female. Length: 6.7-16.3 mm; width: 3.7-8.3 mm. Size and body-shape: wider than males, mainly at the posterior third. Head: clypeus wider; distance between eyes slightly wider; punctures in head and pronotum with different distribution and deepness; lamellae equal to or shorter than flagellum. Legs: protibiae shorter and wider, teeth of outer margin wider; mesotibiae wider at the apex, mesotibial apical transverse carina at the postero-external surface commonly complete and prominent; metatibiae wider, mainly on the apex; not carinated on inner margin; tarsi cylindrical and equally wide in all legs. Abdomen: the pygidium may differ from the male in the shape and roundness, and this difference varies among the species. Male. Length: 6.5-14.7 mm; width: 3.5-7.2 mm. Head: Lamellae generally longer or equal to flagellum, in a few cases shorter; clypeal lateral projection, when present, may be more pronounced than in the female of certain species. Legs: protibiae with two or three teeth; posterior margin of metafemur generally straight but may be produced medially in some species (Fig. 10), metatibiae widened towards apex; carinated along the inner margin entirely or excepting the apex; the inner margin commonly straight towards apex, in some cases is produced abruptly from the sub-basal or medial portion (Fig. 10); metatibial inner margin not carinated in a few cases; apex setose throughout the inner surface but in a few cases glabrous; on posterior surface, one or two transverse carinae and discontinu ous longitudinal carina may be present or absent (Figs 11-12), pair of apical spurs equal to or different in size from each other, the shorter one may be fusiform or truncated (Figs 46-47); pro- and mesotarsi enlarged (in L. tarsalis also the metatarsi), protarsi commonly wider than mesotarsi and two-fold wider than metatarsi (except for L. unicolor and L. macropelma Bates); tarsi shiny or opaque. Abdomen: ventrites III, IV and/or V ornate in some species, with different-sized protuberances or sulcated (as in L. testaceipennis Moser, L. spiniventris Moser, L. pseudospiniventris Cherman, sp. n., L. grossii Cherman, sp. n. and L. sulcoventris Cherman, sp. n.); pygidium more or less angled than that of the female. Parameres: basal region (BR) grooved at its longitudinal midline; the groove width varies depending on the species; parameral split at three different levels: apical third, medially (2/3) or basally (1/3) (Figs 48, 49, 50); outer margin of parameres sometimes furnished with medial (Fig. 49) and/or apical projections (Fig. 48); may be apically narrowed (Fig. 51) or not; inner margins of parameres straight, divergent, or convergent; apex of parameres indistinct or with several distinctive shapes: harpoon-like; spatula-like, fusiform, etc.; in harpoon-like parameres, apical length varies in relation to the total length of the parameres; in lateral view parameres convex, concave, or straight from the parameral split (Figs 52-55); when straight, the parameres and the basal region may be coplanar or not coplanar.

Etymology.

The name Liogenys is composed of the Greek words λείος (leios: smooth) and γένυς (genys: mentum) referring to smooth or glabrous mentum ( Guérin-Méneville 1838; Harold 1869a). The International Code of Zoological Nomenclature ( ICZN 1999), Article 31.2, says that "A species-group name, if it is or ends in a Latin or Latinized adjective [ …], must agree in gender with the generic name with which it is at any time combined". Also, Article 30.1.2 says that: "A genus-group name that is or ends in a Greek word transliterated into Latin without other changes takes the gender given for that word in standard Greek dictionaries". Liogenys is feminine based on the Greek “génys, géneion” ( Smith and Ruiz-Manzanos 2010). Historically, Liogenys was incorrectly treated as masculine by some authors ( Guérin-Méneville 1831, Blanchard 1851, Harold 1869b, Moser 1918, Moser 1919, Moser 1921a, b, Moser 1924, Gutiérrez 1951, Frey 1965, Frey 1969, Frey 1970, Frey 1973). However, Burmeister (1855), Blackwelder (1944), Evans (2003) and Keith (2004) correctly considered the name to be feminine. According to this, all species names must be made feminine, and in this work we have changed them as required.

Distribution and habitats.

Liogenys is a South American genus with 69 species. Only one species has been collected in Sicily: Liogenys excisa (Reitter, 1918). However, according to Baraud (1977, 1992) this species must have been occasionally introduced from South America, as it has never been seen after that. Keith and Lacroix (2003) compared Peritryssus excisus Reitter with L. palpalis (Eschscholtz, 1822) and synonymized these genera. They mentioned that the description of L. obesula Gutiérrez matches that of L. excisa , but they did not synonymize these species as they had not examined the type of L. obesula .

Liogenys occurs from Panama, northern Colombia and northwestern Venezuela (10°N) through southern South America, including Chile (39°S) and Argentina (46°S). The species occur in almost all biogeographical environments and at altitudes up to 4,100 m in Bolivia (16°S) and 4,000 m in Chiriqui, Panama (9°N). The species richness is concentrated mainly in Brazil, with 34 species already recorded plus 13 for which descriptions are being prepared, and in Argentina, with 33 species in addition to 23 awaiting description. Bolivia holds ten species (plus three still undescribed); Para guay, eleven species; Chile, seven species (plus one undescribed); Colombia, Panama and Venezuela, three species: L. gebieni Moser; L. quadridens Fabricius and L. macropelma ) (plus three new species for which descriptions are being prepared); Peru, L. leechi Frey; and Uruguay L. pallens Blanchard. There are no records of Liogenys from Ecuador (Fig. 88).

Discussion.

The Neotropical Diplotaxini included in the interactive key form a well-established clade and the features shared among them are discussed in Cherman et al. (2016). Some of those features have exceptions, as follows: elytral suture generally narrowed at post-scutellar level (except in Homalochilus punctatostriatus Blanchard) and protibiae with an apical spur (except in Liogenys tarsalis ). Furthermore, a common feature in Neotropical Diplotaxini , the enlarged tarsi in males, covered ventrally by pads of abundant bristles, is also seen in non Neotropical Diplotaxini as in Apogonia Kirby, Ceratogonia Kolbe, Dichecephala Brenske and in a few Diplotaxis .

Liogenys and related genera.

The genera most closely related to Liogenys are Pacuvia , Pachrodema , and Homalochilus ( Cherman et al. 2016). Like species of Pacuvia , Liogenys has the anterior margin of the clypeus emarginate; metasternum with sparse scales laterally (as in L. obscura Blanchard, L. densicollis Moser; L. pallens and L. forcipata ) and the outer margin of metacoxae parallel to the elytral margin. Liogenys is distinguished from Pacuvia in that the latter shows a coplanar shape of the frons and clypeus in dorsal view; the maxillae with less than four teeth (except in P. philippiana Gutiérrez); the labium longer than wide (in common with L. sinuaticeps ), distal labial palpomere more globose than the preceding, the ligula straight anteriorly, surface of mentum smooth (without any excavation); pronotal length equal to the length of tarsomeres I, II and III together (in common with L. unicolor and L. macropelma ); pronotum narrower than the base of elytra; prothorax bristled and/or scaly abundantly posteriorly; innermost gap between elytral ridges wider than the adjacent; distance between meso- and metacoxae more than two-fold the metacoxa length (in common with L. kuntzeni Moser); protibial apical tooth parallel to longitudinal axis while basal and/or medial tooth oblique to longitudinal axis, only one longitudinal carina on protibia; basal apophysis of metacoxae not produced posteriorly (beyond the margin of trochanter); basal metatarsomere less than one-half the size of tarsomere II; propygidium completely hidden by the elytra; pygidium twice as wider as it is long. In males, metatibiae narrowed subapically and inner margin not produced (in common with L. sinuaticeps , L. tarsalis and L. forcipata ). With Pachrodema , Liogenys shares the trapezoidal shape of the labium and its distal palpomere not globose; ligula emarginate anteriorly, mentum surface excavated, ligula shorter than the mentum excavation; pronotum longer than the length of tarsomeres I, II and III together; pronotum anteriorly slightly narrowed forming a depressed ring (in common with L. kuntzeni , L. flavida Moser, L. calcarata Frey, L. kadleci Frey; L. palpalis , L. hirta Gutiérrez and L. wagenknechti Gutiérrez); the inner gap between elytral ridges narrower or equal in width as the adjacent; inner margin of protibiae concave, protibial basal and middle teeth perpendicular to the longitudinal axis, two longitudinal carinae. Liogenys is distinguished from Pachrodema in that the latter shows clypeus rounded or sub-emarginate, never forming anterior tooth-like projections; sensorial area of the maxillary distal palpomere grooved and in a dorso-lateral position (except P. lucida Blanchard); constriction between pro- and pterothorax prominent; distance between meso- and metacoxae equal to metacoxae length (in common with L. concolor (Blanchard)); apical tooth of protibiae oblique to the longitudinal axis; inner margin of mesotibiae concave; lateral margin of metacoxae oblique towards pygidium; metatibial inner margin bent and produced apically; apex surface convex at the insertion point of the tarsomere, gap between apical spurs wider than the base of a single spur. Homalochilus shares the same features with Liogenys as well as Pachrodema . Additionally, the lateral margin of metacoxae is parallel to the elytral margin. Males of H. niger Blanchard show metatibiae straight and produced apically. Liogenys is distinguished from Homalochilus in that the latter shows a shorter body, up to three times longer than the pronotum (in common with L. concolor ); labrum longer than ventral face of clypeus; pronotum forming a visibly depressed ring anteriorly, pronotal anterior angles slightly ( H. niger ) or noticeably ( H. punctatostriatus ) produced; punctures of pronotum not umbilicate, pronotum wider than the base of elytra; distance between meso- and metacoxae equal to metacoxal length (in common with L. concolor ); pygidium glabrous (in common with L. sinuaticeps and L. unicolor ), but punctures not umbilicate. In males, basal region of parameres longer than the parameres length beyond the split point. The frons of H. punctatostriatus is longer than the clypeus, clypeus sublobed anteriorly (not emarginate) and ventrite V is longer than ventrite IV (an exception among the Diplotaxini , with all ventrites equally long).

Biological notes.

Liogenys species, as well as most of the Melolonthinae, are root-feeding as larvae, while adults feed on leaves and exhibit nocturnal activity ( Gutiérrez 1951, Britton 1957, Morón et al. 1997, Evans 2002, Morón 2004). Biezanko et al. (1949) mentioned adults of L. densicollis damaging corn in Rio Grande do Sul (Brazil). However, we suggest that this record should be considered doubtful because among the huge number of L. densicollis specimens studied (60 specimens from 10 museums: AMNH, CEMT, CMNC, IADIZA, MLPA, MZSP, NHMB, SDEI, VMDZ and ZMHB), the geographical records found were only from Argentina and Bolivia. Silva et al. (1968) mentioned L. tibialis in Rio Grande do Sul feeding on leaves of peach-tree. Chilean Liogenys were recorded together with Pacuvia species feeding on the following shrubs: Peumo, Cryptocarya alba (Molina) Looser ( Lauraceae ), Litre, Lithraea caustica (Molina) Hook. et Arn. ( Anacardiaceae ) and Quillay, Quillaja saponaria Molina ( Rosaceae ) ( Gutiérrez 1951).

Of the 34 species of Liogenys now known in Brazil, only five are associated with crops. In Rio Grande do Sul, Cherman et al. (2011) recorded four species: Liogenys concolor Blanchard (= L. obesa Burmeister, syn. n.) and L. fusca Blanchard in oat crops; L. bidenticeps Moser and L. sinuaticeps in ryegrass crops. According to Cherman et al. (2014), the abundance of L. sinuaticeps is higher in non-cultivated than in cultivated fields, unlike L. bidenticeps and L. concolor . In Mato Grosso do Sul state, adults of L. bidenticeps have been collected in light traps localized between cultivated and non-cultivated fields ( Rodrigues et al. 2014), while larvae are associated with corn and soybean crops ( Rodrigues et al. 2011). Only L. fusca and L. suturalis (Blanchard) have been recorded as agricultural pests, mainly in the “Cerrado”, a Brazilian savannah biome. Liogenys fusca was found damaging corn and soybean in Mato Grosso do Sul, Mato Grosso, and Goiás States ( Rodrigues et al. 2008, Santos et al. 2008, Costa et al. 2009, Ávila et al. 2014). Liogenys suturalis damages corn, wheat, and oats in Mato Grosso do Sul (Santos and Avila 2009). Rodrigues et al. (2016) recorded adults of L. fusca feeding and mating in Anacardiaceae , suggesting that these plants have an important role in the reproduction of this species. These authors cited that the native plants Urundeuva, Myracrodruon urundeuva ( Allemão) Engl.; Aroeira-vermelha, Schinus terebinthifolius Raddi and Gonçalo-alves, Astronium fraxinifolium Schott represent an important natural source of food and reproduction, whereas the Cajueiro plant, Anacardium occidentale Linnaeus, represents an alternative food source as it is introduced.

Although Liogenys richness is huge in Argentina, research concerning species occurrence is scarce, including that related to crop pests ( Mojica 2014). This might be because the first record of Liogenys damaging soybean plants was recent, in 2006 in Cordoba Province ( Fava et al. 2008). However, there is a record from 1940 of L. cribricollis Moser adults feeding on leaves of Aguaribay, Schinus molle Linnaeus ( Anacardiaceae ) in Villa Maria, Córdoba ( Cordo et al. 2004). Some labels on the specimens studied during this work provided information about the collection method and/or collection environment (Table 2).