Megasoma elephas (Fabricius, 1775)

Ratcliffe, Brett C. & Morón, Miguel-Angel, 2005, Larval Descriptions Of Eight Species Of Megasoma Kirby (Coleoptera: Scarabaeidae: Dynastinae) With A Key For Identification And Notes On Biology, The Coleopterists Bulletin 59 (1), pp. 91-126 : 110-115

Megasoma elephas (F.), 3rd instar ( Figs. 67–80 )

Description based on three third instar larvae reared from eggs laid by female collected in México: Quintana Roo, Felipe Carrillo Puerto, 26-XII-1984, O. Canul (IEXA); one cast skin of third instar larva with same data (IEXA); two third instar larvae collected in México: Chiapas, Ocosingo, Yaxchilán, 27/ 28-V-1981, 120– 140 m, E. Fuentes (IEXA); one cast skin of third instar larva reared to pupa, collected in México: Chiapas, Cacaohatán, Finca San José de la Victoria, 31-VIII-1981, J. Valenzuela (IEXA).

Description. Head. Maximum width of head capsule 15.6–17.2 mm. Surface of cranium dark brown to black, coarsely rugopunctate, punctures deep. Frons uniformly punctate ( Fig. 67 ), each side with 4 posterior frontal setae, 70–80 anterior frontal setae, 3 exterior frontal setae, 6–7 centrolateral setae, and 6 anterior angle frontal setae; remaining cranial surface with 4 dorsoepicranial, short setae, 45–60 epicranial setae, and 8–10 paraocellar setae on each side. Clypeus trapezoidal, with 2 lateral setae on each side, 10–12 anterior setae, 40–50 discal setae, and 10–12 posterior clypeal setae. Labrum slightly asymmetrical, rounded at sides, with 4–6 scattered, anterior labral setae, 10 posterior setae, 4–5 central setae, and 4–5 lateral setae on each side. Ocelli vaguely indicated. Epipharynx ( Fig. 68 ) with fused zygum and epizygum forming strongly raised, nearly longitudinal, sclerotized tubercle on haptomerum; heli and plegmatia absent; right chaetoparia with mixture of 92–120 spine-like setae and 25–35 sensillae; left chaetoparia with mixture of 70–90 spine-like setae and sensillae; acroparia with 6–10 straight, long, thick setae on right side and 4–6 straight, long, thick setae on left side; both acanthoparia with vaguely indicated, abraded tormae of 8–9 setae; both gymnoparia wide, sclerotized, abraded; pedium wide, epitorma poorly defined; dexiotorma wide, angular, with enlarged and narrowed inner side; laeotorma with enlarged and narrowed inner side, and widely rounded pternotorma; dexiophoba formed by 8–12 setae located near haptolochus; laeophoba between haptolachus and inner side of laeotorma formed by 10–16 setae; sclerotized plate or right nesium elongate, strongly sclerotized and strongly raised; sense cone of left nesium represented by large, longitudinal, well-sclerotized plate with rounded anterior side and truncate posterior side; crepis indicated by weak, poorly sclerotized shallow sulcus. Scissorial area of right mandible ( Fig. 69 ) slightly abraded, with 3 scissorial teeth clearly separated by notches or sinuses, and 1 basal, rounded tooth; molar area with 3 poorly defined lobes, calx prominent, brustia sparse. Scissorial area of left mandible ( Fig. 70 ) slightly abraded, with 3 scissorial teeth vaguely separated by notches or sinuses, and 1 basal wide, rounded tooth; molar area with 2 wide lobes, brustia sparse, acia short with rounded apex. Stridulatory area of each mandible well-marked by almost 35–40 fine striae. Mala ( Fig. 71 ) with apical uncus of galea well-developed with 3 conical unci fused at their bases at apex of lacinia; maxillary stridulatory area ( Fig. 72 ) with irregular row of 8 wide, truncated or rounded teeth, and wide, truncate anterior process. Labium ( Fig. 71 ) with numerous long, strong setae located near sides and short, spine-like setae at middle and proximal border; hypopharynx with right anterior lateral process of hypopharyngeal sclerome moderately developed, raised, curved, heavily sclerotized; left hypopharyngeal lateral lobe with patch of 8–10 posterior lateral short setae, and 1 line of 20 slender setae. Last antennal segment on dorsal surface ( Fig. 73 ) with 8–10 sensory spots; ventral surface with 10–12 spots. Thorax. Pronotum with wide, irregular, reddish brown, lateral scleromes, each with row of 20–25 long setae ( Fig. 77 ) and about 70–80 long, slender setae near anterior and posterior borders, setae not arranged in definite rows. Mesonotum with transverse group of 48–52 long, slender setae, 80–90 long, slender setae in irregular rows, and 1 group of 40–45 slender setae on each side; metanotum with 2 transverse groups of 40–50 long, slender setae, and 44–52 long, slender setae arranged in irregular row. Thoracic spiracles 1.8–2.2 mm long and 2.25–2.70 mm wide; lobes of respiratory plate contiguous, directed posteriorly. Spiracular bulla rounded, convex, irregular, scarcely prominent. Tarsal claws ( Fig. 74 ) similar on all legs, with rounded apex, each bearing 2 internal, long, thick, basal setae and 2 external, long, thick, preapical setae. Abdomen. Dorsum of segment I with 1 row

112 THE COLEOPTERISTS BULLETIN 59(1), 2005

of 70–75 mixed, medium sized and long, slender setae, and 1 row of 140–150 long, slender setae. Dorsum of segment II with 1 transverse group of 70–80 long, slender setae mixed with 130–140 short, spine-like setae, 1 transverse group of 12–14 long, slender setae mixed with 80–90 short, spine-like setae, and 1 transverse group of 100–120 long, slender setae mixed with 140–160 short, spine-like setae. Dorsa of segments III–VI each with 1 transverse group of 30–32 long, slender setae mixed with 120–130 short, spine-like setae, 1 transverse group of 6–8 long, slender setae mixed with 70–80 short, spine-like setae, and 1 transverse group of 50–56 long, slender setae mixed with 140–150 short, spine-like setae. Dorsum of segment VII with 1 transverse group of 120–130 long, slender setae mixed with 130–140 short, spine-like setae, and 1 transverse group of 60–70 long, slender setae mixed with 70–80 short, spine-like setae. Dorsum of segment VIII ( Fig. 73 ) with 12– 14 long, slender setae on each side, 8–10 long, slender setae near anterior border, 70–76 long, slender setae near posterior border, and more than 200 short, spine-like setae widely distributed. Dorsum of segment IX with longitudinal rugosities and 12 long, slender setae near anterior border, 20 long, slender setae on each side, 50–60 long, slender setae near posterior border, and more than 250 short, spine-like setae widely distributed. Dorsum of segment X with 20 long, slender setae near posterior border, 8 medium sized, slender setae scattered at center, and more than 160 short, spine-like setae widely distributed. Venter of abdominal segments I–VI each with irregular rows of 40–50 mixed, long and short, slender setae; venter of segments VII–VIII each with irregular rows of 40–45 mixed, long and medium sized, slender setae; venter of segment IX with groups of 50–60 mixed, long and medium sized, slender setae on each side. Raster without pallidia and septula, with 4–6 medium sized, slender setae on campus, teges formed by 32–35 short, slender setae; cuticle clearly rugose. Barbula formed by 22–25 long, slender setae. Lower anal lip with about 80–86 mixed, long and medium sized, slender setae. Upper anal lip with 260–280 mixed, short and medium length and short, spine-like setae. Spiracles of segments I–VIII ( Fig. 77 ) progressively enlarged (2.10–2.80 mm long; 1.35–2.40 mm wide); lobes of respiratory plate contiguous ( Fig. 75 ) directed anteriorly. Spiracular bulla convex, irregularly rounded, weakly prominent; respiratory plate with about 90–95 irregular shaped holes across any diameter. Approximate dorsal body length 125–225 mm.

Second-instar Larva. Based on one second-instar larva reared from egg laid by female collected in México: Quintana Roo, Felipe Carrillo Puerto , 26-XII-1984, O. Canul, fixed at 97 days age ( IEXA) .

Description. Similar to third-instar larva except as follows: maximum width of head capsule 7.9 mm. Ocelli vaguely indicated. Epipharynx with 8–9 plegmatia finely marked; acroparia with 7–8 straight, long, thick setae on right side, and 4 straight, medium sized, thick setae on left side; both acanthoparia with 10 short, curved, spinelike setae. Scissorial area of both mandibles with teeth more clearly defined. Last antennal segment with 9–13 dorsal sensory spots. Dorsal and lateral vestiture of thoracic and abdominal segments with distinctive, long, slender setae. Prothoracic spiracles 1.0 mm wide, 0.65 mm long. Abdominal spiracles slightly enlarged toward posterior segments (0.75 mm wide, 0.50–0.70 mm long). Tarsal claws with 4 long, slender setae. Approximate dorsal body length 60 mm.

First-instar Larva. Based on one first-instar larva reared from egg laid by female collected in México: Quintana Roo, Felipe Carrillo Puerto , 26-XII-1984, O. Canul, fixed at 12 days age ( IEXA) .

Description. Similar to second-instar larva except as follows: maximum width of head capsule 3.5 mm. Scissorial area of left mandible with second tooth large, dorsally outstanding; scissorial area of right mandible with second tooth triangular, dorsally outstanding. Last antennal segment with 8–9 dorsal sensory spots. Sclerotized plates on sides of pronotum absent. Eclosion spine on each side of metanotum small, conical, surrounded by 4 short, slender setae. Thoracic spiracles 0.25 mm wide, 0.18 mm long. 114 THE COLEOPTERISTS BULLETIN 59(1), 2005

Abdominal spiracles similar in size: 0.21 mm wide, 0.14 mm long, without definite bulla (Fig. 76). Approximate dorsal body length 13 mm.

Male Pupa. Based on one pupa reared from third instar larva collected in México: Chiapas, Cacaohatán, Finca San José de la Victoria , 31-VIII- 1981, 800 m , coffee-cacao plantation, J. Valenzuela, pupated 27-VI-1982, fixed 1-VII-1982 ( IEXA) .

Description. Body shape elongate, oval, stout, exarate ( Fig. 78 ). Color dark reddish orange. Entire body with fine, velvety-gold vestiture. Head: Bent sharply beneath thorax, mouthparts directed ventrally; antennae, mandibles, palpi and eye canthus recognizable. Compound eyes sunken, scarcely visible. Frontoclypeus with strong, wide, massive horn-like structure bent upward at distal third, apex widely forked in rounded branches, and anterior surface with fine, transverse ridges. Anterior border of clypeus truncate, with rounded borders. Pronotum: Form nearly transverse, with wide, anteromedial, rounded tubercle, surface finely annulate and with transverse ridges and granules on surface. Each anterolateral border with large, semiconical projection directed obliquely forward, with annulate, fine ridges on surface. Pterothecae closely appressed, curving ventrally around body, extending posteriorly to abdominal segment II or III. Legs: Protibia with 3 projections on exterior border. Mesotibia with 2 small tubercles on external side, and 2 apical, rounded tubercles. Metatibia with 3 small, rounded projection on external side, and 2 apical, rounded tubercles. Tarsomeres delineated, protarsi longer that meso- and metatarsi. Abdomen: 9 segments visible. Spiracles of segment I hidden by wing theca and by oblique fold; spiracles on segments II–IV elongate, annulate, sclerotized, pigmented, directed cephalad; spiracles on segments V–VII occluded, rosetiform, not sclerotized or pigmented; spiracle on segment VIII absent. Tergal area of segments I–VI with 6 pairs of deep and wide dioneiform organs or ‘‘gin traps’’ (each 8–9 mm width). Tergum VII with 1 pair of less marked dioneiform organs on anterior border. Tergum VIII with 2 ovate, transverse, deep impressions toward basolateral border. Posterior border of terga VII–VIII with rows of small, rounded tubercles. Last segment with 2 symmetrical, fleshy, ventrolateral folds covered by dense, fine, golden vestiture. Last sternite and genital ampulla partially hidden by folds. Body length 88 mm; maximum width 43 mm.

Female Pupa. Based on cast skin of pupa reared from egg laid 22-I-1985 by female collected in México: Quintana Roo, Carrillo Puerto, 26-XII-1984, O. Canul ( IEXA) .

Description. Similar to male pupa except that head and pronotum do not have horns or large tubercles; tibiae and tarsi shortened; genital ampulla wide, rounded. Body length not measurable.

Remarks. The third instar larva is robust and measures 34–44 mm in width between the metathorax and the first two abdominal segments. As a consequence, the head (14–17 mm in width in frontal view) looks partially sunken into the prothorax and is clearly smaller than it. The larvae of M. elephas are similar in a number of structures 116 THE COLEOPTERISTS BULLETIN 59(1), 2005

Figures

Figs. 67–75. Megasoma elephas, third instar. 67) Head, frontal view; 68) epipharynx; 69–70) mandibles, ventral view; 69) right and 70) left; 71) right maxilla and hypopharynx, dorsal view; 72) detail of maxillary stridulatory area; 73) distal segment of antenna, dorsal view; 74) right posterior tarsal claw, external view; 75) second right abdominal spiracle. Fig. 76. Megasoma elephas, first instar, second right abdominal spiracle. Figs. 67–71, 75, bar ¼ 1 mm. Figs. 72–74, 76, bar ¼ 0.5 mm.

Fig. 77. Megasoma elephas, third instar, lateral view. Bar ¼ 10 mm. Setal pattern simplified.

Fig. 78. Megasoma elephas, male pupa, lateral view. Bar ¼ 10 mm.