Macrodactylus nigripes Bates, 1887

García, Agustín Aragón- & Morón, Miguel Ángel, 2010, Description Of The Larvae Of Three Species Of Macrodactylus Dejean (Coleoptera: Scarabaeidae: Melolonthinae) From Mexico, With Notes On The Reproductive Behavior Of Macrodactylus Ocreatus Bates, The Coleopterists Bulletin 64 (3), pp. 193-200 : 196-198

Macrodactylus nigripes Bates, 1887 ( Figs. 13–15 )

Description is based on seven third instars collected in Mexico: Puebla, Chignahuapan, San Antonio Matlacahuales (19°45′04″N, 98°05′46″W), 1,999 m, 24-I-2007, from soil in corn field, A. Aragón and A. N. Cortés (DAGAM, IEXA).

Description. Head. Maximum head capsule width 2.4–2.5 mm, approximate dorsal body length 22–24 mm. Surface of cranium nearly smooth, light yellow. Frons ( Fig. 13 ) on each side with 1 exterior frontal seta, 2 posterior frontal setae, 1 anterior frontal setae, and 1 anterior angle frontal seta; remaining cranial surface with 4–5 dorsoepicranial setae, 1 epicranial setae, and 6 paraocellar setae on each side. Clypeus trapezoidal, with 2 lateral setae on each side and 2 anterior setae. Labrum nearly symmetrical, rounded at sides, with 5 posterior setae, 2 central setae, and 4 lateral setae on each side. Epipharynx ( Fig. 14 ) with dark, irregular elongate epizygum; haptomerum with 7 short stout heli; each acanthoparia with 10 curved spine-like setae; acroparia with 7 long setae; corypha with 5 setae; each plegmatium with 6–8 short plegmata; right chaetoparia with 18 long slender setae; left chaetoparia with 28 long, stout setae; pedium narrowed; dexiophoba absent; laeophoba with 6–7 filaments; laeotorma short; pternotorma short, narrowed; sclerotized plate large; sense cone rounded; crepis weakly indicated; haptolachus with few sensilla, without setae. Scissorial area of each mandible with 2 scissorial teeth S1 and S2 fused, scissorial notch and S3 clearly defined; molar area with 3 lobes best defined in left mandible; mandibular stridulatory area absent. Mala with apical uncus of galea well developed, and 3 conical unci fused at their bases at apex of lacinia; maxillary stridulatory area with 9 small, sharply pointed teeth. Hypopharyngeal sclerome asymmetrical, produced on right side into a strong process. Last antennal segment with 1 ovate sensory spot on dorsal surface, 2 spots on ventral surface.

Thorax. Pronotum and mesonotum with transverse rows of scattered slender setae, but without spine-like setae. Thoracic spiracles light yellow, 0.20 mm long and 0.25 mm wide; lobes of respiratory plate curved, widely separated, directed posteriorly; spiracular bulla small, weakly convex. Tarsal claws similar in fore and middle legs, long with acute apex, each bearing 1 internal long seta and 1 external long seta; tarsal claw in hind legs slightly shorter than preceding, with rounded apex.

Abdomen. Dorsa of segments I-VI with mixture of few rows of long setae and many spine-like setae; dorsa of segments VII-X without spine-like setae, but each with 30 long and short slender setae. Venter of abdominal segments I-VIII each with a transverse row of 9 long setae; venter of segment IX with 6 slender setae. Respiratory plates of segments I-VIII progressively shorter (0.24–0.26 mm long; 0.12–0.13 mm wide); lobes of respiratory plates separated, directed anteriorly. Spiracular bulla slightly convex, weakly prominent. Raster ( Fig. 15 ) with one pair of longitudinal short palidia (0.22 mm total length, 0.05 mm maximum width); each palidium with 6–8 sharply pointed short pali; tegilla formed by 18–20 stout hamate setae; campus with 5–6 stout, long setae; barbula formed by moderate number of slender setae. Lower anal lip deeply cleft on midline; anal slit Y-shaped.

Remarks. Larvae of M. nigripes are similar to those of M. mexicanus by the number of frontal setae and size of abdominal spiracles, but the presence of 6–7 heli on the epipharynx and 6–8 pali on each palidia will serve to separate M. nigripes .

Distribution and Habits. Macrodactylus nigripes is recorded from localities in Chiapas, Coahuila, Hidalgo, México, Michoacán, Morelos, Oaxaca, Puebla, Querétaro, Tlaxcala, and Veracruz at elevations from 1,000 to 2,550 m. Males and females are commonly found in large number on leaves, flowers, and fruits of beans, corn, apple, pear and peach trees,wild grasses, and species of Senecio , Baccharis , and Lupinus L. ( Fabaceae ) (Arce-Pérez and Morón 2000).

Figures

Figs. 13–18. Third instars of Macrodactylus nigripes (13–15) and Macrodactylus ocreatus (16–18). 13) Head, frontal view; 14) Epipharynx; 15) Raster. 16) Head, frontal view; 17) Epipharynx; 18) Raster. Scale bars = 1 mm.