Megasoma vogti Cartwright, 1963

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 : 104-106

Megasoma vogti Cartwright , 3rd instar ( Figs. 43–54 )

Description based on remnants of one third instar larvae reared from egg laid by female collected in U.S.A., Texas, Live Oak Co, X-1989, D. W. Sundberg (UNSM).

Description. Head. Maximum width of head capsule 8.4 mm. Surface of cranium dark brown, rugopunctate,punctures large, deep.Frons uniformly punctate ( Fig.43 ), each side with 5–7 posterior frontal setae, 6–7 anterior frontal setae, 7–9 exterior frontal setae, and 4–5 anterior angle frontal setae; remaining cranial surface with 1 dorsoepicranial, short seta, 30–36 epicranial setae, and 2–3 paraocellar setae on each side.Clypeus trapezoidal, with 2 lateral setae on each side, 2 anterior setae, and no posterior clypeal setae. Labrum slightly asymmetrical, subovate, rounded at sides, with row of 21 anterior labral setae, not interrupted at middle, no posterior setae, 4 central setae, and 2 lateral setae on each side. Ocelli not apparent. Epipharynx ( Fig. 44 ) with fused zygum and epizygum forming poorly raised, longitudinal, sclerotized tubercle on haptomerum; heli and plegmatia absent; right chaetoparia with mixture of 70 spine-like setae and 15 sensillae;left chaetoparia with mixture of less than 80 spine-like setae and sensillae; acroparia with 10 straight, long, thick setae on right side and 16 straight, long, thick setae on left side; right acanthoparia with 9 short, curved, spine-like setae; left acanthoparia with 5 short, curved, spine-like setae; pedium wide, epitorma poorly defined; dexiotorma wide, with large, truncate, inner side; laeotorma short, with narrowed inner side and widely rounded pternotorma; dexiophoba not apparent; laeophoba between haptolachus and inner side of laeotorma formed by 3 setae; sclerotized plate on right nesium elongate; sense cone on left nesium represented by large, longitudinal, well-sclerotized plate with rounded anterior side and truncate posterior side; crepis not defined. Scissorial area of right mandible ( Figs. 46, 49 ) slightly abraded, with 3 scissorial teeth clearly separated by notches, and 1 basal, rounded tooth; molar area with 3 poorly defined lobes; calx prominent, brustia sparse. Scissorial area of left mandible ( Figs. 47–48 ) slightly abraded, with 3 scissorial teeth clearly separated by notches, 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 23–25 fine striae. Mala ( Fig. 45 ) with apical uncus of galea well-developed, and 3 conical unci fused at their bases at apex of lacinia; maxillary stridulatory area ( Fig. 50 ) with 7 small, truncate or round teeth, and wide, truncate anterior process. Labium ( Fig. 45 ) 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 16 posterolateral, short setae and 1 line of 12, slender setae. Last antennal segment on dorsal surface ( Fig. 51 ) with 6 sensory spots; ventral surface with 6 spots. Thorax. Pronotum with wide, irregular, reddish brown, lateral scleromes and about 90 long, slender setae near anterior border and 40 medium sized, slender setae near posterior border, setae not arranged in definite rows. Mesonotum with 3 transverse groups of 25–70 long, slender setae and 4 groups of 15–40 medium sized, slender setae; metanotum with 4 transverse groups of 30–70 long, slender setae, 3 groups of 10–12 medium sized, slender setae, and 1 group of 23 short, spine-like setae, setae not arranged in rows. Thoracic spiracles 0.60 mm long and 0.78 mm wide; lobes of 106 THE COLEOPTERISTS BULLETIN 59(1), 2005

respiratory plate contiguous, directed posteriorly. Spiracular bulla rounded, convex, irregular, scarcely prominent. Tarsal claws ( Fig. 52 ) similar on all legs, with acute apex, each bearing 2

internal, long, thick, basal setae and 2 external, long, thick preapical setae. Abdomen. Dorsum of segment I with 2 rows of 26–30 short, spine-like setae, 4 rows of 20–34 medium sized, slender setae, and 2 rows of 30–34 long, slender setae, and more than 100 long setae on each side. Dorsa of segments II–VI each with 75–90 long setae mainly on sides and 70–100 spine-like, short setae mixed with long setae; on middle third these setae form more or less regular row of 20–22 long setae. Dorsum of segment VII with more than 120 long, slender setae, more than 80 short, spine-like setae on each side, and transverse, anterior row of 26 slender, long setae. Dorsum of segment VIII with 1 row of 24 long, slender setae, more than 100 short, spine-like setae, and 70 long setae on each side. Dorsum of segment IX with 2 rows of 18–26 long, slender setae, and 40 long, slender setae and more than 90 short, spine-like setae on each side. Dorsum of segment X with approximately 120 short, spine-like setae and 50 long, slender setae on each side. Venter of abdominal segments I–II each with 5 rows of 35–40 long, slender setae and 2 rows of 28–32 medium sized, slender setae; venter of segments III–V each with 1 row of 22 long, slender setae and 2 rows of 25–30 medium sized, slender setae; venter of segments VI–VIII each with 86 long and medium sized, slender setae on each side; venter of segment IX with 70 long and medium sized, slender setae on each side. Raster without pallidia and septula, with 18 long, slender setae on campus, teges formed by 12 medium sized, slender setae; cuticle slightly rugose. Barbula formed by 25–28 long, slender setae. Lower anal lip with about 100 mixed long and medium size, slender setae. Upper anal lip with more than 80 mixed short, spine-like setae and long, slender setae, mainly on sides. Spiracles of segments I–VIII progressively shorter (0.7– 0.6 mm long; 1.0– 0.8 mm wide); lobes of respiratory plate contiguous ( Fig. 53 ), directed anteriorly. Spiracular bulla convex, irregularly rounded, weakly prominent ( Fig. 54 ); respiratory plate with about 30 irregularly shaped holes across any diameter. Approximate dorsal body length not measurable.

Remarks. Larvae of M. vogti are similar to those of M. punctulatus by the presence of 3–5 anterior angle frontal setae, 7 maxillary stridulatory teeth, 5–6 dorsal sensory spots on the last antennal segment, acanthoparia with 5–9 setae, dorsum of abdominal segment II with spine-like setae, lobes of respiratory plates of spiracles contiguous, and bulla rounded and scarcely prominent. However, the 6–7 anterofrontal setae, absence of posterior setae on the labrum, 70 setae on the right chaetoparia, dexiotorma widened with the inner side truncate, dorsum of abdominal segment I with spine-like setae, 18 setae on the campus, and abdominal spiracles progressively smaller towards segment VIII will serve to separate M. vogti .

Distribution and Habits. Adults of M. vogti have been recorded in a small number of localities in Hidalgo Co., Jim Wells Co., and Live Oak Co., Texas, U.S.A., and Salinas Victoria, state of Nuevo León, and Buenavista, state of Tamaulipas, México, between 100 to 400 meters in elevation ( Cartwright 1963, 1970; Hardy 1972). Vegetation in these areas is comprised of mesquite, thorn shrubs, cacti, and occasional small trees. Males and females were collected from July to October either being attracted to lights, found on the soil surface, or on branches of ‘‘mezquite’’ ( Prosopis juliflora [Swartz] Mimosaceae ).

Figures

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.