Megasoma cedrosa Hardy, 1972

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 : 106-110

Megasoma cedrosa Hardy , 3rd instar ( Figs. 55–66 )

Description based on two third instar larvae reared from eggs laid by females collected in México: Baja California, Hwy 1, 1 km N Rancho El Progreso, vicinity Hwy marker 115, 21-VIII-1998, R. A. Cunningham and J. D. Bever collectors; eggs laid 22–26-VIII-1998; larvae fixed 22-VII-1999 (UNSM, IEXA).

Description. Head. Maximum width of head capsule 7.3 mm. Surface of cranium dark brown, densely punctate, punctures deep. Frons irregularly punctate ( Fig. 55 ), each side with 3–4 posterior frontal setae, 10–11 anterior frontal setae, 2–4 exterior frontal setae, and 3 anterior angle frontal setae; remaining cranial surface with 1 row of 7–10 setae near dorsoepicranial suture, 10–16 epicranial setae, and no paraocellar setae on each side. Clypeus trapezoidal, with 2 lateral setae on each side, 5–6 discal setae and no posterior clypeal setae. Labrum slightly asymmetrical, rounded at sides, with row of 20–24 anterior labral setae, vaguely interrupted at middle, 8–10 posterior setae, 2 central setae, and 4 lateral setae on each side. Ocelli not apparent. Epipharynx ( Fig. 56 ) with fused zygum and epizygum forming moderately raised, longitudinal, sclerotized tubercle on haptomerum; heli and plegmatia absent; right chaetoparia with mixture of 64–70 spine-like setae and 24–30 sensillae; left chaetoparia with mixture of 90 spine-like setae and 5–8 sensillae; acroparia with 14– 108 THE COLEOPTERISTS BULLETIN 59(1), 2005

16 straight, medium sized, thick setae on right side and 11–12 straight, short, thick setae on left side; right acanthoparia with 10 short, curved, spine-like setae; left acanthoparia with 13–14 short, curved, spine-like setae; pedium wide, epitorma poorly defined; dexiotorma narrowed toward acute inner side; laeotorma short, with narrowed inner side and widely rounded pternotorma; dexiophoba not apparent; laeophoba between haptolachus and inner side of laeotorma not apparent; sclerotized plate on right nesium irregularly shaped; sense cone on left nesium represented by large, longitudinal, well-sclerotized plate with rounded anterior side and sinuated posterior side; crepis not defined. Scissorial area of right mandible ( Fig. 57 ) slightly abraded, with 2 scissorial teeth clearly separated by notches, 2 vaguely defined, rounded teeth, and 1 basal, rounded tooth; molar area with 3 poorly defined lobes, calx prominent, brustia sparse. Scissorial area of left mandible ( Fig. 58 ) slightly abraded, with 2 scissorial teeth clearly separated by notches, 1 scarcely defined tooth, and 1 basal, wide, rounded tooth; molar area with 2 wide lobes, brustia sparse and acia short with rounded apex. Stridulatory area of each mandible well-marked by about 22–26 fine striae. Mala ( Fig. 60 ) with apical uncus of galea well-developed and 3 conical unci fused at their bases at apex of lacinia; maxillary stridulatory area ( Fig. 59 ) with 5 small, rounded teeth, and wide, truncate anterior process. Labium with numerous, long, strong setae located on sides and short, spine-like setae at middle and proximal border; hypopharynx with right anterior lateral process of hypopharyngeal sclerome strongly developed, raised and curved, heavily sclerotized; left hypopharyngeal lateral lobe with patch of 22 posterolateral, short setae and 1 line of 10 slender setae. Last antennal segment on dorsal surface ( Fig. 61 ) with 4 sensory spots; ventral surface with 5 spots. Thorax. Pronotum with wide, irregularly shaped, yellowish, lateral scleromes and about 80 long, slender setae near anterior border, setae not arranged in definite rows; spine-like, short setae absent. Mesonotum with 3 transverse groups of 32–64 long, slender setae; spine-like, short setae absent. Metanotum with 4 transverse groups of 38–72 long, slender setae, setae not arranged in rows. Thoracic spiracles 0.65 mm long and 0.85 mm wide; lobes of respiratory plate separated by distance slightly shorter than dorsoventral diameter of bulla, directed posteriorly. Spiracular bulla rounded, convex, irregular, scarcely prominent. Tarsal claws ( Fig. 64 ) similar on all legs, with acute apex, each bearing 2 internal, long, thick, basal setae and 2 external, long, thick preapical setae. Abdomen. Dorsa of

segments I and II with vaguely defined, transverse rows of 20–24 long, slender setae, spine-like, short setae absent. Dorsa of segments III–VI each with mixture of 85–95 long setae and 70–90 spine-like, short setae. Dorsa of segments VII–IX with about 75 long, slender setae and 70 short, spine-like setae, progressively spaced toward posterior borders of each segment. Dorsum of segment X with spine-like setae on anterior half and mixture of 40–42 long, slender setae and about 80 short, spine-like setae on posterior half. Venter of abdominal segments I–II each with 4 rows of 25–30 long, slender setae, and 2 rows of 20–24 medium sized slender setae; venter of segments III– V each with 1 row of 15 long, slender setae, and 2 rows of 15–20 medium sized, slender setae; venter of segments VI–VIII each with 50–54 long and medium sized, slender setae on each side; venter of segment IX with 50 long and medium sized, slender setae on each side. Raster without pallidia and septula ( Fig. 65 ), with 12–14 long, slender setae on campus, teges formed by 20–24 medium sized, slender setae; cuticle slightly rugose. Barbula formed by 20–25 long, slender setae. Lower anal lip with about 120 mixed long and short, slender setae. Upper anal lip with more than 100 mixed short and long, slender setae, mainly on sides. Spiracles of segments I–VIII progressively shorter (0.7– 0.5 mm long; 0.9– 0.6 mm wide); lobes of respiratory plate separated ( Fig. 63 ), directed anteriorly. Spiracular bulla slightly convex, irregularly rounded, weakly prominent ( Fig. 62 ); respiratory plate with about 32 irregularly shaped holes across any diameter. Approximate dorsal body length 65–67 mm.

Second-instar Larva. Based on one second-instar larva reared from egg laid by female collected in México: Baja California, Rosario de Arriba , 22-VIII-2002, G. Nogueira, fixed at 190 days age ( IEXA) .

Description. Similar to third-instar larva except as follows: maximum width of head capsule 4.5 mm. Last antennal segment with 4 dorsal sensory spots. Dorsal and lateral vestiture of thoracic and abdominal segments with distinctive, long, slender setae. Prothoracic spiracles 0.35 mm wide, 0.20 mm long. Abdominal spiracles I–VIII progressively shorter (0.28– 0.25 mm wide, 0.22– 0.20 mm long). Approximate dorsal body length 50 mm.

First-instar Larva. Based on two first-instar larva reared from egg laid by female collected in México: Baja California, Rosario de Arriba , 22-VIII-2002, G. Nogueira, fixed at 19 days age ( IEXA) .

Description. Similar to second-instar larva except as follows: maximum width of head capsule 2.7–2.8 mm. Sclerotized plates on sides of pronotum absent. Eclosion spine on each side of metanotum small, conical. Thoracic spiracles 0.14 mm wide, 0.10 mm long. Abdominal spiracles kidney-shaped, without definite bulla; spiracles I–VIII progressively shorter (0.14 mm wide, 0.10 mm long). Approximate dorsal body length 14–15 mm.

Remarks. Larvae of M. cedrosa share similar characters with the larvae of M. thersites and M. elephas : 3–4 posterior frontal setae, 2 setae on each side of clypeus, 7–10 setae on posterior border of labrum, and bulla rounded and slightly prominent. Megasoma cedrosa may be distinguished by the presence of 10 frontal setae, reduced number of epicranial setae (10–16 on each side), right chaetoparia with 64–70 setae, 5 maxillary stridulatory teeth, last antennal segment with 4 dorsal sensory spots, dorsa of abdominal segments I and II without spine-like setae, and 12–14 setae on the campus. The increased number of frontal and epicranial setae, 8 maxillary stridulatory teeth, dorsum of abdominal segment II with short, spine-like setae, spiracles of abdominal segments progressively larger toward segment VIII, lobes of respiratory plate of spiracles contiguous, and increased head and body size will distinguish the larvae of M. elephas from M. cedrosa .

Distribution and Habits. Megasoma cedrosa (¼ M. lenczyi Cartwright ) has been recorded in a small number of localities in Baja California, México, including the type locality on Cedros Island, San Felipe, Rosario de Arriba, and the vicinity of El Progreso 110 THE COLEOPTERISTS BULLETIN 59(1), 2005

between 100–600 meters in elevation ( Hardy 1972; Cartwright 1976). Adults have been

collected from August to October on thorn shrubs, under soil, or on branches of Acacia sp. (Mimosaceae) ( Fig. 66 ). Males are active during the morning, but near noon they walk to the base of the trunk and dig holes in the soil for protection when the air temperature becomes extreme. When the air temperature decreases, males return to the branches of their host tree for gumming sap from the branches or to await the emergence of females (G. Nogueira, pers. comm., to MAM; R. Cunningham, pers. comm., to BCR).

Figures

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.

Fig. 66. Megasoma cedrosa on branch of Acacia sp. Photo by David Russell.