Megasoma, Kirby, 1825

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 : 124

Key to the Third Instar Larvae of Megasoma in North and Central America

1 Maxilla with 4 or 8 stridulatory teeth. Diameter of abdominal spiracles progressively enlarged posteriorly, mainly from segment V to segment VIII. Maximum width of cranium 11–18 mm - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2

1 9 Maxilla with 5–7 stridulatory teeth. Diameter of abdominal spiracles progressively reduced posteriorly, mainly from segment V to segment VIII. Maximum width of cranium 7–9 mm - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5

2 Bulla of spiracles transverse, raised, with acute apex ( Figs. 12–13 ). Last antennal segment with 10–14 dorsal sensory spots. Frons with 1 posterior frontal setae on each side. Dexiotorma narrow, elongate ( Fig. 2 ). Maximum width of head capsule 11.3 mm - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - M. pachecoi Cartwright

2 9 Bulla of spiracles vertical, slightly prominent, rounded ( Fig. 75 ). Last antennal segment with 8–11 dorsal sensory spots. Frons with 2–4 posterior frontal setae on each side. Dexiotorma wide, angular ( Fig. 68 ). Maximum width of head capsule 15–18 mm - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3

3 Frons with 70–80 frontal setae. Dorsum of abdominal segment I without short, spine-like setae, only with long, slender setae. Campus with 4–6 long, slender setae - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - M. elephas (F.)

3 9 Frons with 4 or 8 frontal setae. Dorsum of abdominal segment I with mixture of long, slender setae and short, spine-like setae. Campus with 20–28 setae - - - - - - - - - 4

4 Each tarsungulus with 4 setae. Frons with 4 frontal setae. Maxilla with 8 stridulatory teeth. Last antennal segment with 8 dorsal sensory spots - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - M. occidentalis Bolívar y Peltain, Jiménez-Asffla, and Martínez

4 9 Each tarsungulus with 2 setae. Frons with 8 frontal setae. Maxilla with 4 stridulatory teeth. Last antennal segment with 11 dorsal sensory spots - - - - - - - - - M. actaeon (L.)

5 Lobes of respiratory plates of spiracles separated ( Figs. 39 , 62–63 ). Frons with 3–4 posterior frontal setae on each side. Acanthoparia with 10–14 setae - - - - - - - - - - - - - - - - - 6

5 9 Lobes of respiratory plates of spiracles contiguous or nearly so ( Figs. 26 , 53– 54 ). Frons with 5–7 posterior frontal setae at each side. Acanthoparia with 5–9 setae - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 7

6 Maxilla with 7 stridulatory teeth ( Fig.34 ). Last antennal segment with 7 dorsal sensory spots ( Fig. 36 ). Dorsa of abdominal segments I–II with mixture of long, slender setae and short, spine-like setae. Frons with 2 dorsoepicranial setae and 46 epicranial setae on each side; anterior frontal setae lacking - - - - - - - - - - - - - - - - - - - - - - - - - M. thersites LeConte

6 9 Maxilla with 4 stridulatory teeth ( Fig. 59 ). Last antennal segment with 4 dorsal sensory spots ( Fig. 61 ). Dorsa of abdominal segments I–II with only long, slender setae. Frons with 7–10 dorsoepicranial setae and 10–16 epicranial setae on each side, and with 10–11 anterior frontal setae - - - - - - - - - - - - - - - - - - - - - - - - - - M. cedrosa Hardy

7 Frons with 6–7 anterior frontal setae. Dexiotorma wide, truncate ( Fig. 44 ). Dorsum of abdominal segment I with mixture of long, slender setae and short, spine-like setae. Bulla of spiracles irregularly rounded, vaguely trilobed ( Figs. 53–54 ). Campus with 18 setae - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - M. vogti Cartwright

7 9 Frons without anterior frontal setae. Dexiotorma narrow, elongate ( Fig. 17 ). Dorsum of abdominal segment I with long, slender setae, without spine-like setae. Bulla of spiracles slightly convex, rounded ( Fig. 26 ). Campus with 28–30 setae - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - M. punctulatus Cartwright

Figures

Figs. 1–14. Megasoma pachecoi, third instar. 1) Head, frontal view; 2) epipharynx; 3–4) mandibles, ventral view, 3) right and 4) left; 5) right maxilla and hypopharynx, dorsal view; 6) detail of unci of lacinia; 7) detail of maxillary stridulatory area; 8–9) distal segment of antenna, 8) dorsal view and 9) ventral view; 10–11) left tarsal claws, external views, 10) middle and 11) posterior; 12) second left abdominal spiracle; 13) detail of bulla of spiracle, ventral view; 14) microstructure of respiratory plate (5003). Figs. 1–5, bar ¼ 1 mm. Figs. 6–13, bar ¼ 0.5 mm.

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.

Figs. 29–40. Megasoma thersites, third instar. 29) Head, frontal view; 30) epipharynx; 31–32) mandibles, ventral view, 31) right and 32) left; 33) distal part of right maxillary mala; 34) detail of maxillary stridulatory area; 35) right maxilla and hypopharynx, dorsal view; 36–37) distal segment of antenna, 36) dorsal view and 37) ventral view; 38) left posterior tarsal claw, external view; 39) second right abdominal spiracle; 40) microstructure of respiratory plate (5003). Figs. 29–32, 35, bar ¼ 1 mm. Figs. 33–34, 36–39, bar ¼ 0.5 mm.

Figs. 55–65. Megasoma cedrosa, third instar. 55) Head, frontal view; 56) epipharynx; 57–58) mandibles, ventral view, 57) right and 58) left; 59) detail of maxillary stridulatory area; 60) left maxilla, ventral view; 61) distal segment of antenna, dorsal view; 62–63) second right abdominal spiracle, 62) anterolateral view and 63) lateral view; 64) left posterior tarsal claw, external view; 65) last abdominal segment, ventral view with raster. Figs. 55–58, 60, 65, bar ¼ 1 mm. Figs. 59, 61–64, bar ¼ 0.5 mm. Fig. 65, bar ¼ 5 mm.

Figs. 16–26. Megasoma punctulatus, third instar. 16) Head, frontal view; 17) epipharynx; 18–19) mandibles, ventral view, 18) right and 19) left; 20–21) mandibles, dorsal view, 20) left and 21) right; 22) left maxilla and hypopharynx, dorsal view; 23–24) distal segment of antenna, 23) dorsal view and 24) ventral view; 25) left posterior tarsal claw, external view; 26) second right abdominal spiracle. Figs. 16–22, bar ¼ 1 mm. Fig. 26, bar ¼ 0.5 mm.

Figs. 43–54. Megasoma vogti, third instar. 43) Head, frontal view; 44) epipharynx; 45) left maxilla and labium, ventral view; 46–47) mandibles, ventral view, 46) right and 47) left; 48–49) mandibles, dorsal view, 48) left and 49) right; 50) detail of maxillary stridulatory area; 51) distal segment of antenna, dorsal view; 52) left posterior tarsal claw, external view; 53–54) second right abdominal spiracle, 53) lateral view and 54) left ventrolateral view. Figs. 43–49, bar ¼ 1 mm. Figs. 50–54, bar ¼ 0.5 mm.