Casignetus MacLeay, 1819

Silva, Alessandra C. G. & Grossi, Paschoal C., 2019, Immature stages of the genus Casignetus MacLeay, 1819 (Coleoptera: Lucanidae: Lucaninae), Zootaxa 4568 (3), pp. 501-519 : 502-504

Casignetus MacLeay, 1819

Third instar description ( Fig. 52 ). Body: Scarabaeiform, light yellow, length 21.98–28.27 mm. Head: Head capsule ( Figs. 1 , 10–12 ) globose, hypognatha, color yellow-testaceous. Epicranial suture present, coronal suture inverted “V-shape”, long; frontal sutures extending to the base of the antennae, with curved apex. Cranium surface with 3 dorsoepicranial setae, 1–2 lateroepicranial setae, and 1 anteroepicranial seta on each side. Each side of frons with 1 seta at anterior frontal angle, 2–3 externofrontal setae, 2 anterofrontal setae and 2 posterofrontal setae, stemmata absent. Foramen magnum rounded, measuring 60% of the diameter of the cephalic capsule. Gula transverse, membranous. Antennae with 3 antennomeres, first antennomere longer than the length of second and third together, dilated distally, less pigmented than others. Last antennomere smaller. Antennomeres 1 and 2 with scattered setae; last antennomere ( Fig. 59 ) surrounded by 4 subapical setae and 1 apical seta. Clypeus ( Figs. 13–15 , 64 , 74 , 87 ) trapezoidal, sclerotized, medial line more sclerotized, right and left margins with 2 long medioclypeal setae and 1 lateroclypeal seta approximately half the length of the other two setae. Labrum ( Figs. 13–15 , 64 , 74 , 87 ) ellipsoidal, more sclerotized laterally, with 7 elongate setae, 2 anterolabral, 4 mediolabral, and 1 posterolabral, usually smaller than other setae. Epipharynx ( Figs. 2 , 16–18 , 65 , 75 , 88 ) asymmetric; haptomerum with 3–11 sensillae, helus absent, pedium glabrous, acroparia present with about 3–6 setae, achantoparia with 6–8 thicker setae, corypha with 6–9 setae; right chaetoparia with 48–54 setae, denser than left chaetoparia (27–39 setae); protophoba with 10–15 sensillae, and 2–4 setae; laeotorma and dexiotorma fused; pternotorma subtriangular shaped, convex, with sharp apex, and slightly asymmetrical; epitorma long, slender; haptolachus with three nesia and with few short setae, left nesium smaller than right, central nesium more developed, about four times bigger than others, apex more sclerotized. Mouthparts protruding. Mandibles ( Figs. 4 , 19 –30, 66–69, 78–81, 91–94) subtriangular, asymmetrical, strongly sclerotized with teeth decreasing in size from apex to base; apical and inner margins black including molar area, lighter near middle and on external margins. Accessory condyle present. Inner angle with a subtriangular ventromolar process; external angle strongly sclerotized, and with rounded prostartis. Mola present, with distal lobes projected; molar area concave. Right mandible ( Figs. 19–20, 23–24, 27 –28, 66–67, 78–79, 91–92) with 4 incisor teeth; dorsal surface with 2–4 dorsolateral setae, and 9–16 dorsomolar setae; ventral surface with 2–3 ventrolateral setae, 3–6 ventromedial setae, and 1–4 ventromolar setae. Left mandible ( Figs. 21– 22, 25–26 , 29–30, 68–69, 80–81, 93–94) with 5 incisor teeth; dorsal surface with 2–4 dorsolateral setae, and 10–16 dorsomolar setae; ventral surface with 2 ventrolateral setae, 3–5 ventromedial setae, and 4–6 ventromolar setae. Maxillae ( Figs. 5 , 33, 36, 39 , 60 , 70–71 , 76–77 , 89–90 ) with separate galea and lacinia, and with many long and robust setae. Galea articulated, with uncus surrounded dorsally by a group of long setae; lacinia elongate. subconical, and with apex unciform, strongly pigmented, and with a group of long inner setae, shorter setae at middle, and below uncus. Maxillary palpi with 4 palpomeres, palpomere 1 with 1 seta; palpomere 2–3 each with 2 setae, palpomere 4 glabrous; stipe elongate, with 5–10 setae; cardo with 1 short seta. Hypopharynx ( Figs. 3 , 32, 35, 38 , 60 , 71 , 82–83 , 95–96 ) with densely setose, marginal setae of medium to long size, central setae shorter; scleroma with 2 strongly sclerotized tooth-shaped projections ( Fig. 60 ), right scleroma more developed, with 13– 16 setae on right margin, and 27–28 setae on left margin. Labium ( Figs. 31, 34, 37 , 70 , 84 , 97 ) with mentum and prementum fused with 4 long subapical setae, central setae shorter than lateral setae, and with some short scattered subapical setae; 2 long medial setae, and 1–3 long lateral setae on each side. Labial palpi with 2 palpomeres and few short setae. Thorax. Prothorax ( Fig. 61 ) larger than mesothorax and metathorax, divided into two portions by a transverse medial groove, anterior portion with 2 rows of setae and a group of lateral setae; posterior portion of prothorax, and other thoracic segments with only 1 row of setae. Thoracic spiracle C-shaped, with concavity facing the anterior region, located laterally on the prothorax under a setose tubercle. Legs ( Figs. 72–73 , 85–86 , 98–99 ) well developed, prothoracic leg smaller than mesothoracic and metathoracic leg. Coxae ( Figs. 6 , 40–42 , 62 ) globose, with posterior face excavated, with few basal setae. Trochanter fused to femur in prothoracic and mesothoracic legs, articulated in metathoracic legs. Distal femoral face dilated, with sclerotized anterior face. Metatrochanter with posterior distal tip pointed, sclerotized on anterior distal end. All legs with long setae on tibiae. Tarsungulus sclerotized, with sharp apex, and 2 subapical setae. Par stridens ( Figs. 6 , 40–42 , 62 ) located on external face of mesocoxae with 51–74 teeth, formed by a slightly arched, longitudinal row of robust and sclerotized teeth, clearer on extremities, on proximal end teeth may form 3–4 slightly rows or a little scattered distally. Plectrum ( Figs. 7 , 43–45 , 63 ) formed by a transverse row of 44–50 suboval teeth on inner metatrochanteral face, closer and thinner distally. Abdomen. Abdomen ( Fig. 52 ) 10-segmented, with a transverse row of long setae on each segment, and many short setae from segment 1–6; abdominal spiracles C-shaped, located laterally from segment 1–8, facing anterior region, decreasing in size posteriorly; segment 10 obliquely projected relative to the longitudinal axis of the larval body; raster ( Figs. 8 , 46–48 ) with 270–290 setae, disc glabrous; palidium absent. Anal opening longitudinal, located between two lobes. Anal lobes ( Figs. 49–51 ) with glabrous central area, sometimes presenting 5–6 short setae, setae thinner on anterior margin.

Material. Casignetus humboldti (1♂ and 5♀, Nova Friburgo, Rio de Janeiro, Brazil), C. spixi (1♂ e 1♀, Nova Friburgo, Rio de Janeiro, Brazil), C. lindei (1♀, Ponta Grossa, Paraná, Brazil), all in CERPE.

Pupae description ( Figs. 9 , 53–58 ). Dorsal view ( Figs. 53, 56 ). Body. Form elongate, length about 2.5 times the width, male with 3.5 cm, and females with 1.9–2.3 cm in length. General color yellow, yellowish white on female. Head. Partially covered by pronotum on male, completely on female in dorsal view. Thorax. Surface smooth, shiny. Pronotum subtrapezoidal; on female transverse, presenting an anteromedian expansion; length measuring 1.2 times the length of mesonotum and metanotum together, convex, with rounded angles, with a group of setae above posterior angles, and on anterior and posterior borders, medial region presenting a longitudinal groove, deeper on extremities, anteromedial margin expanded. Mesonotum and metanotum ranging from yellowtestaceous to brown. Posterior margin of mesonotum widely rounded, with few marginal setae. Metanotum with a median longitudinal groove, converging apically in female; margins rounded. Pterothecae (pt 1 and pt 2) subparallel with slightly rounded sides, base wide apex sharp, with soft longitudinal striae; pt? completely visible, pt? partially visible; both pterothecae partially visible in female. Podothecae partially visible. Abdomen 9 segmented; abdominal tergites wider in female; tergites 1 and 2 darker, tergites 1–4 with a setose lateral tubercle on both sides, tubercle decreasing in size posteriorly; tergites surface moderately wrinkled; tergites 1–8 with a transverse row of setae; tergite 8 narrower, about 1.5 times longer than others; tergite 9 with 2 laminate lobes; genitalia visible. Female with tergite 9 presenting shorter urogomphi, and rounded sides; genitalia not apparent.

Lateral view ( Figs. 9 , 54, 57 ). Head. Form hypognathous. Cephalotheca , ophthalmothecae and ceratothecae visible, similar color, translucent. Cephalotheca with an apical depression in female. Ceratothecae elongate, thick, curved; shorter, and thicker in female. Mandibles backward reaching abdomen; shorter, and perpendicularly projected in female. Thorax. Podothecae (pod 1, pod 2, and pod 3) long, extending up to half of abdomen, completely visible, shorter in female. Abdomen. Sternites 1–4 presenting elliptical and oblique spiracles along longitudinal body axis, decreasing in size posteriorly; genitalia like-spiral, apex extending up to about half of sternite 9.

Ventral view ( Figs. 55, 58 ). Head. Mandibles clearly visible, hiding cephatothecae, and ophthalmothecae, with incurved apex. In female all structures are completely visible, cephalotheca with subtrapezoidal apex, and ophthalmothecae parallel. Thorax. Podothecae completely visible, with femora slightly oblique (inclination pod?> pod? <pod?), pterothecae partially visible. Abdomen. Sternites smooth, visible from 2–9; sternite 2 partially visible, presenting a small median tubercle; anteromedian margin of sternite 3 with a subconic tubercle, with apex directed forward; sternite 9 with a median lobe, from which genitalia originates; urogomphi subquadrangular; apex weakly serrated, with four small teeth; female with urogomphi shorter, rounded, and genitalia not apparent.

Material. Casignetus humboldti (1♂ and 1♀, Nova Friburgo, Rio de Janeiro, Brazil), C. lindei (1♀, Tibagi, Paraná, Brazil). CERPE.

Remarks. Casignetus is a Neotropical genus restricted to the southeastern and southern regions of Brazil, in Brazilian Atlantic Forest, Parana Forest, and Araucaria angustifolia Forest provinces sensu Morrone (2006), and high altitudes, generally above 1000 m, as well as adjacent areas of Argentina and Paraguay. In relation to the distributional gradient from Southeastern to Southern Brazil, the three species need further studies and possibly there is a complex of cryptic species within C. spixi , with two separate populations, from the mountains of Rio de Janeiro state and Southern Brazil and Argentina respectively ( Grossi 2018).

Figures

FIGURES 52–58. Casignetus immatures. 52, Third instar (lateral); 53–55, female pupae (dorsal, lateral, ventral); 56–58, male pupae (dorsal, lateral, ventral). Scale bars = 1 cm. Photographs: P.C. Grossi.

FIGURES 1–5. Schematic drawings of Casignetus larval head and the mouthparts and their components. 1, Head capsule (frontal); 2, epipharynx; 3, hypopharynx; 4, mandibles; 5, maxillae.

FIGURES 10–18. Head capsule (frontal), labrum and epipharynx of Casignetus larvae. 10, Casignetus humboldti; 11, C. spixi; 12, C. lindei; 13, labrum of C. humboldti; 14, labrum of C. spixi; 15, labrum of C. lindei; 16, epipharynx of C. humboldti; 17, epipharynx of C. spixi; 18, epipharynx of C. lindei. Scale bars = 1 mm.

FIGURES 59–63. Casignetus larvae. 59, Last antennomere; 60, maxillae and hypopharynx (anterior); 61, prothorax (lateral); 62, mesocoxae (external); 63, metatrochanter (internal). Scale bars: 59 = 0.2 mm; 60–61 = 1 mm; 62–63 = 0.5 mm. Photographs: 59, M. Cherman; 60–63, A. Guedes.

FIGURES 64–73. Casignetus humboldti larvae. 64, Labrum; 65, epipharynx; 66–67, right mandible (ventral, dorsal); 68–69, left mandible (dorsal, ventral); 70, maxillae and labium (ventral); 71, maxillae and hypopharynx (dorsal); 72, mesothoracic leg (external); 73, metathoracic leg (internal). Scale bars = 1 mm. Photographs: M. Cherman.

FIGURES 74–86. Casignetus spixi larvae. 74, Labrum 75, epipharynx 76–77, left maxilla (dorsal, ventral); 78–79, right mandible (ventral, dorsal); 80–81, left mandible (dorsal, ventral); 82–83, hypopharynx (dorsal, lateral); 84, labium; 85, left mesothoracic leg (external); 86, left metathoracic leg (internal). Scale bars = 1 mm. Photographs: D. Basílio.

FIGURES 87–99. Casignetus lindei larvae. 87, Labrum; 88, epipharynx; 89–90, left maxilla (dorsal, ventral); 91–92, right mandible (ventral, dorsal); 93–94, left mandible (dorsal, ventral); 95–96, hypopharynx (dorsal, lateral); 97, labium; 98, right mesothoracic leg (external); 99, right metathoracic legs (internal). Scale bars = 1 mm. Photographs: A. Guedes.

FIGURES 19–27. Mandibles of Casignetus larvae. 19–22, Casignetus humboldti right mandible (ventral, dorsal), and left mandible (dorsal, ventral); 23–26, C. spixi right mandible (ventral, dorsal), and left mandible (dorsal, ventral); and 27–30, C. lindei right mandible (ventral, dorsal), and left mandible (dorsal, ventral). Scale bars = 1 mm.

FIGURES 31–39. Mouthparts of Casignetus larvae. 31–33, Casignetus humboldti labium, hypopharynx, and left maxilla (dorsal), respectively; 34–36, C. spixi labium, hypopharynx, and left maxilla (dorsal), respectively; 37–39, C. lindei labium, hypopharynx, and left maxilla (dorsal), respectively. Scale bars = 1 mm.

FIGURES 6–9. Schematic drawings of Casignetus larval parts. 6, Mesocoxae (external) with indications of pars stridens; 7, metatrochanter (internal) with indications of plectrum; 8, last abdominal segment (ventral) with indications of raster and anal opening; 9, pupa (lateral) with indications of the main structures.

FIGURES 40–51. FIGURES 40–45. Stridulatory organs Casignetus larvae. 40, Pars stridens of C. humboldti; 41, pars stridens of C. spixi; 42, pars stridens of C. lindei; 43, plectrum of C. humboldti; 44, plectrum of C. spixi; 45, plectrum of C. lindei. Scale bars = 1 mm. FIGURES 46–51. Last abdominal segment of Casignetus larvae. 46, Raster of C. humboldti; 47, raster of C. spixi; 48, raster of C. lindei; 49, anal lobes (posterior) of C. humboldti; 50, anal lobes (posterior) of C. spixi; 51, anal lobes (posterior) of C. lindei (dilated anal region due to the presence of excrement at death). Scale bars = 1 mm.