Liogenys bidenticeps Moser, 1919

Rodrigues, Sérgio Roberto, Fuhrmann, Juares, Gomes, Elias Soares & Amaro, Ricardo Aparecido, 2017, Description of immatures and mating behavior of Liogenys bidenticeps Moser, 1919 (Coleoptera: Melolonthidae: Melolonthinae), Revista Brasileira de Entomologia 61 (4), pp. 339-348 : 340-342

Liogenys bidenticeps Moser, 1919

Third instar ( Figs. 1–38 ). Length: 17.3 mm (15–18 mm) ( Fig. 1 ). Head ( Fig. 2 ), width 2.2–2.6 mm; epicranial suture slightly distinct in the posterior half; stemmata absent. Each head side ( Figs. 2, 3 ) with 4 dorsoepicranial setae (des); 2 lateroepicranial setae (les); 3 anteroepicranial setae (aes); 9–10 ventroepicranial setae (ves); 4 posterofrontal setae (pfs); 3 lateralofrontal (or externofrontal) setae in the anterior angles (lfs); 2 anterofrontal setae (afs); 1 anteroclipeal seta (acs); 2 lateroclipeal setae (lcs); 2–3 posterolabral setae (pls); 4 laterolabral setae (lls); 1 mediolabral seta (mls); 2 anterolabral setae (als). Cranium, clypeus, and labrum ( Fig. 9 ) with many sensilla.

Antennifer cylindrical, with about 5 sensilla. Antenna with 4 antennomeres ( Figs. 4–8 ): I short (length/width = 2), with 1 dorsal and 1 ventral sensillum; II long (l/w = 3.3–3.5), with 2 dorsal setae, 2 dorsal sensilla, 1 externoproximal sensillum, 1 externodistal sensillum, 3 ventral sensilla; III short (l/w = 2.3–2.4), with 3 dorsal sensilla, 3 ventral sensilla, 1 externodistal sensillum, 2 internodistal sensilla, and with a ventrodistal process bearing a dorsal sensorial spot, and 3 dorsal sensilla; IV short (l/w = 2.2–2.4), with 1 ventral sensillum, 2 external sensilla, 1 internal sensillum, 1 dorsal sensorial spot, and 2 ventral sensorial spots; distal sensorial area with 7 sensilla.

Epipharynx ( Figs. 10–12 ). Corypha : epizygum indistinct; clithrum absent. Haptomerum: zygum as a cross-bar; with 5 heli, 2 spine-like marginal setae on each side, and 9 sensilla. Paria: right acroparia with 17–19 setae, left acroparia with 15 setae; each acantoparia with 11–14 setae; gymnoparia well defined and with some sensilla; right chaetoparia with 68–77 setae, left chaetoparia with 47–51 setae; plegmatia present, proplegmatia absent; each side with long phobae; dexiotorma longer than laeotorma; laeotorma with short pterotorma, apotorma and epitorma inconspicuous. Pedium longer than wide. Haptolachus: each side of crepis with 3 sensilla; nesium internum tubercle-like and with 4 sensilla; nesium externum tabulate; each side with long phobae not contiguous with paria phobae; medial area with some minute phobae, lateral area with some minute tubercle and sensilla. The posterior pre-oral area with a pair of 3 sensilla.

Mandible ( Figs. 13–18 ). Incisor with 3 teeth, the two proximal slightly distinct and separated from each other by a small groove. The dorsal area with 1 seta and 2 sensilla; ventroproximal area with a rugous stridulatory area; medioexternal area with a seta. Right scrobe (externoproximal area) with 4–5 setae; left scrobe with 8–12 setae. Ventral processes well developed. Right molar with a row of 12 dorsoproximal setae; with 4 chisel-like teeth; well-developed brustia. Left molar with a row of 5 dorsoproximal setae; with an anterior semicircular chisel-like tooth, a ventromedial small tooth, acia absent, and an acute large calx.

Maxillae ( Figs. 19–21 ). Galea and lacinia separated by suture. Galea with an uncus and a row of 6 tooth-like internoventral setae; lacinia with 3 unci; internodorsal area of mala with a row of 7 dorsal tooth-like setae. Stipe with stridulatory area bearing 12–13 acute teeth. Palp with 4 palpomers: I with an external seta; II with a ventroproximal sensillum; III with an external seta, a ventral seta, and 2 ventral sensilla; IV with an internodistal sensillum, distal sensorial area with 16–18 sensilla.

Hypopharynx ( Figs. 11, 12 , 20 ) with asymmetrical sclerite, right lateral with 5 setae, left with 8 setae; left, right, and posterior areas of sclerite with prominent phoba; posterior area with 5 sensilla.

Labium ( Figs. 11, 12 , 20, 21 ). Each side of submentum with a long seta and sensillum; mentum with transversal sclerite, each side of sclerite with 4 lateral setae and a medial seta; prementum with about 15 anterior setae; ligula with 5 heli, 4 medial sensilla, a small medial tubercle, 10–12 lateral thin setae, and 14 medial tooth-like setae. Palp with two palpomeres: I with 1 dorsal seta and 1 small ventroproximal seta; II with 1 externodistal sensillum, distal sensory area with 10 sensilla.

Thorax. Pro-, meso- and metanotum with 3 lobes each ( Fig. 1 ). Legs ( Figs. 22–27 ). Protibia with two parallel rows of 5 ventral thick setae, each seta inserted in a short process; meso- and metatibia with 2 pairs of thick ventral setae, each seta inserted in an acute process; tarsungulus with 2 lateroventral setae, and with an acuminate apex; protarsungulus longer than meso-, meso- longer than the meta-. Thoracic spiracle ( Fig. 28 ) with about 8 perforations in the longitudinal and ventral radii, and 12 perforations in the dorsal radius, perforations oblong and more or less regular; length 0.41 mm, width 0.29 mm; bulla wider than the distances between respiratory plate arms.

Abdomen. With 10 segments; I–VIII with 3 dorsal lobes, IX–X without dorsal divisions. Spiracles ( Figs. 29–36 ) I–VII similar to each other, length 0.4 mm, width 0.3 mm, and with 9–12 perforations in all radii (dorsal, longitudinal, ventral); VIII smaller than the others, length 0.3 mm, width 0.25 mm, and with 7–5 perforations in all radii. Each side of the raster ( Figs. 37, 38 ) with: tegillum with 27–28 spine-like setae, of which 22 are preseptular setae (anterior to the palidia); barbula indistinct; palidium with 5–7 tooth-like setae, of which the 2–3 anterior setae are small and the other 3–4 posterior setae are long. Segment X ( Fig. 38 ) with a Y-shaped anal opening, each lateroventral anal lobe with 18–21 setae, dorsal anal lobe with 57 setae.

Remarks. Cherman et al. (2011) characterized the palidia of L. bidenticeps , L. fusca , L. obesa , and L. sinuaticeps , in addition to provide the following diagnosis for the genus [addendum hereby noted]: last antennomere with a [dorsal] sensorial spot, mandibles without a ventral stridulatory [striated] area, palidia oblique and anteriorly convergent [or transverse (e.g. L. obesa )], anal opening Y-shaped. It is important to note that the mandibles present an analogous granular stridulatory area even lacking a striated stridulatory area. Mandibles with a ventral stridulatory area formed by minute spine-like granulation (similar to that ornamentation illustrated in Figs. 13, 14, 17 and 18 ) and the absence of a striated stridulatory area are characteristic in larvae of Scarabaeinae and Melolonthinae ( Hayes, 1930; Schiödte, 1874). Böving (1936) described the mandible of Plectris aliena Chapin, 1934 (Macrodactylini) as “having the stridulating area completely lacking.” Larvae of two undetermined species of Plectris (MZSP) were observed in this study and both presented mandibles with granular stridulatory areas. It is possible that the melolonthine mandible descriptions being “without a stridulatory area” (e.g. Böving, 1936; Cherman et al., 2011; Ramirez-Salinas and Castro-Ramirez, 2015) are based only on the absence of a striated area (usually present in Cetoniidae , Dynastinae, and Rutelinae; and characterized by series of parallel and transversal costulation or striation).

Other species of Diplotaxini with known larvae are Diplotaxis puberea (Bates, 1887) (description by Ramirez-Salinas and Castro-Ramirez, 2015); and L. fusca (description by Rodrigues et al., 2016). See identification key for diagnosis.

Examined material. BRAZIL. Mato Grosso do Sul; Aquidauana, rearing in the laboratory G. A. L. Nogueira (collector), 11 third instar larvae preserved on 23.I.2011 ( UEMS), 7 third instar larvae preserved on 06.II.2011 ( MZSP) .

Figures

Figs. 1–8. Liogenys bidenticeps, third instar larva; 1, habitus; 2, head; 3, chaetotaxy of cranium and clypeus; 4−8, antennae; 4, dorsal (antennomere IV detached); 5, internal; 6, external; 7, antennomere II, ventral; 8, antennomere IV, ventral.Scale: 1−3, 0.5mm; 4−8, 0.25 mm.

Figs. 9–12. Liogenys bidenticeps, third instar larva; 9, labrum; 10, epipharynx; 11–12, cibarium (right, left). Scale: 0.5 mm.

Figs. 13–18. Liogenys bidenticeps, third instar larva; 13−15, right mandible (ventral, internal, dorsal); 16−18, left mandible (dorsal, internal, and ventral).Scale: 0.5mm.

Figs. 19–21. Liogenys bidenticeps, third instar larva; 19, maxilla, internal; 20, maxilla, hypopharynx, ligula, dorsal; 21, maxilla, labium, ventral.Scale: 0.5mm.

Figs. 22–36. Liogenys bidenticeps, third instar larva; 22−24, anterior,medial,and posterior legs, external; 25−27, pro-, meso-, and metatarsungulus,dorsal;28, mesothoracic spiracle; 29−36, abdominal spiracles I−VIII. Scale: 22−24, 1 mm; 25−28, 0.5mm; 29−36, 0.1mm.

Figs. 37–38. Liogenys bidenticeps, third instar larva; 37, raster; 38, abdominal segment X, posterior.Scale: 1 mm.