Ancognatha scarabaeoides Erichson, 1847

Vallejo, Fernando & Morón, Miguel Angel, 2008, Description of the Immature Stages and Redescription of the Adults of Ancognatha scarabaeoides Erichson (Coleoptera: Scarabaeidae: Dynastinae), A Member of the Soil White Grub Assemblage in Colombia, The Coleopterists Bulletin 62 (1), pp. 154-164 : 155-162

Ancognatha scarabaeoides Erichson, 1847

Adult

( Figs. 1–7 )

Redescription. Male. Body length: 18.3–25.4 mm; robust, slightly depressed and widened toward posterior half of elytra; head, pronotum, elytra, and legs reddish chestnut brown to shiny black; sternal and abdominal areas ochreous yellow to reddish brown, depending on geographical area. Sexual dimorphism accentuated in anterior legs and in last abdominal segments.

Head. Labrum much reduced, hidden under clypeus. Clypeus enlarged, parabolic, with anterior border strongly upturned. Surface of clypeus and frons with many small punctures ( Fig. 1 ). Frontoclypeal suture incomplete on midline, with two transverse tubercles. Antennae formed by 10 segments; antennal club with 3 segments, longer than preceding 6 segments ( Fig. 2 ). Mandibles with distal part narrowed and elongate, strongly upturned with acute apex. Mentum with ventral surface concave and anterior border deeply sinuate.

Thorax. Pronotum ( Fig. 1 ) wider than long, widely convex, with scattered microscopic punctures; anterior angles nearly straight, not prominent; posterior angles obtuse, widely rounded; basal margin only defined toward the lateral angles. Prosternal process narrowed at base and widened towards apex, with many long setae. Pterosternum covered with many reddish yellow, long setae. Elytra nearly twice longer than wide, convex, with shallow small punctures along the striae, and scattered small punctures on interstriae; epipleural border narrowed throughout length. Protibia ( Fig. 3 ) with 3 tooth-like, short projections on external border and straight preapical inner spur. Meso and metatibiae longer than protibia. Three basal protarsomeres similar in form and size, short and strong; fourth tarsomere wider than third; distal tarsomere much elongate, curved and widened. Inner protarsal claw wider than external claw ( Fig. 4 ).

Abdomen. Fifth sternite clearly longer than preceding sternites, with wide membranose posterior border. Last sternite convex, with posterior border weakly sclerotized near midline. Prepygidium densely covered with reddish, short setae. Pygidium convex, wider than long, shiny, with scattered microscopic punctures, and some erect, long setae across apical border. Genital capsule strongly curved downward; parameres elongate, symmetrical, and deeply notched on preapical external border, with distal part nearly arrow-shaped and apex slightly curved ventrally ( Figs. 5–7 ).

Female. Body length: 16.5–20.7 mm. Similar to male except as follows: pronotum moderately convex; epipleural border ending near the middle of elytra with a noticeable expansion; protibia with 3 tooth-like, acute, long projections on external border; basal protarsomere elongate, protarsomeres 2 to 4 similar in form and size, longer than wide, each shorter than basal one; distal tarsomere much elongate, narrowed; inner protarsal claw slightly longer than external claw, with apex acute and entire; last sternite without membranous area on the midline of distal border.

Remarks. Externally, adults of A. scarabaeoides appear similar to A. atacazo Kirsch , because the dorsal coloration in both species is completely dark brown, without yellow spots. However, the anterior border of the clypeus is contracted to the apex in A. scarabaeoides ( Fig. 1 ), and is broadly rounded in A. atacazo . The pygidium is glabrous in the former species and setose in the latter. The external border of each paramere is strongly emarginated in A. scarabaeoides ( Figs. 5–7 ), whereas it is weakly emarginated in A. atacazo .

Distribution. Panama, Colombia, Ecuador, Peru and Bolivia (Ratcliffe 2003). In Colombia. A. scarabaeoides has a wide distribution in the departments of Antioquia, Atlántico, Boyaca, Caldas, Cauca, Cundinamarca, Huila, Meta, Nariño, Quindio, Risaralda, Santander, Tolima and Valle (Restrepo et al. 2003), but it is more common in the zone with premontane very humid forest (bmh-P) according with the classification system of Holdridge (1987). It is frequently associated with potato fields located above 2,200 m elevation.

Specimens examined. 153 males and 156 females from Colombia: Department of Antioquia, El Carmen de Viboral municipality, Los Garzones pathway, April and May 1995, May 1996, March to May 1996, 2,200 m, potato fields, black light trap, L. A. Henao, C. Restrepo (17 males, 13 females) ; San Vicente municipality, Alto de la Compañía pathway, April and May 1994, 1995, 1996. 2,200 m, potato fields, black light trap, L. A. Henao, C. Restrepo (18 males 11 females) ; El Retiro municipality, La Fe pathway, February to June 1994, 1995, 1996. 2,200 m, mixed cultures, black light trap, L. A. Henao, C. Restrepo (17 males, 11 females) ; La Ceja municipality, around main town, April and May 1994, 1995, 1996, 2,200 m, potato fields, black light trap, L. A. Henao, C. Restrepo (13 males, 15 females) ; La Unión municipality, Montecristo pathway, April and May 1994, 1995, 1996. 2,600 m, potato fields, black light trap, L. A. Henao, C. Restrepo (12 males, 12 females) ; Medellín municipality, Santa Elena, pathways El Perico, Coltejer and Paysandú , 2,550 m, April and May 1994, 1995, 1996, potato fields, black light trap, L. A. Henao, C. Restrepo (10 males, 16 females) . Department of Caldas, Manizales municipality, Maltería , Tesorito-Universidad de Caldas farm, 2,450 m, March to May 2000 –2001, May 2003, potato fields, hand collected in soil, F. Vallejo (20 males, 24 females) ; Manizales municipality, Páramo de Letras, Km 38 Manizales-Bogotá Hwy , Hacienda La Esperanza , 2,900 m, March to May 2000 – 2002, potato fields, hand collected in soil, F. Vallejo (29 males, 25 females) . Department of Tolima, Fresno municipality, Herveo , 3,900 m, March to May 2000 –2003, potato fields, hand collected in soil, F. Vallejo (21 males, 29 females) .

Third instar Larva

( Figs. 8–20 )

Description. Approximate body length 36.3 mm; Maximum width of head capsule: 6.4 mm. Head. Cranium ( Fig. 8 ) reddish yellow, with small punctures, without stemmata, apex of mandibles nearly black; 2 epicraneal setae, 1 posterior frontal seta, and 2 basiantennal setae on each side. Clypeus with 1 anterior seta and 1 exterior seta on each side. Labrum nearly symmetrical, with irregular surface, 4 lateral setae and 1 central seta on each side and 4 setae towards apex. Epipharynx ( Fig. 9 ) ovate, asymmetrical, right margin wider than left margin; zygum irregular; epizygum with 6–8 setae; haptomerum wide, prominent, with 10–12 heli; acroparia with 4 stout, short setae; right chaetoparia with 30–40 sensilla irregulary distributed; left chaetoparia with 20–30 sensilla irregularly distributed; each acanthoparia with 12–14 curved, short setae; both gymnoparia narrowed; without proplegmatia and plegmatia; pedium without laeophoba; dexiotorma short and narrowed; pterotorma slightly curved. Mandibles asymmetrical, basally yellowish, distally blackish; left mandible ( Figs. 10–11 ) with 3 scissorial teeth and 2 well defined molar areas, distal lobe or M1 is wider and higher than basal lobe or M2, basally with a line of 5 short setae; brustia formed by numerous long, slender setae; dorsoexterior region with 5–7 long, slender setae along basal half. Right mandible ( Figs. 12– 13 ) with 3 scissorial teeth and 2 irregularly defined molar lobes M1 and M2; brustia formed by less-dense tufts of slender setae; dorsoexterior region with 5–7 long, slender setae along basal half. Maxilla ( Figs. 14–15 ) with one row of 11 truncate stridulatory teeth bordering stipes, with rounded, anterior process; lacinia with longitudinal row of 3 well developed unci surrounded by 23–30 heli and many slender setae; galea with one acute, apical uncus; maxillary palpus with 4 segments, basal segment short, 2nd and 3rd segments similar in length and form, and apical segment longer than preceding. Labium small; labial palpus with 2 segments, basal segment shorter and wider than apical segment; hypopharingeal sclerome asymmetrical, concave near midline, with right lobe strongly upturned, left lobe with tufts of setae. Antenna ( Fig. 16 ) with 4 elongate segments, 3rd segment with subapical acute projection, apical segment with 4 ovate, dorsal sensory spots.

Thorax. Fore legs shorter than middle legs and middle legs shorter than hind legs. Tarsal claws ( Fig. 17 ) with similar in length and form in the three pairs of legs, claws elongate and acute apically with 4 basal slender setae and 2 preapical setae. Prothoracic spiracle 0.78 mm long and 0.51 mm wide (measured dorsoventrally); lobes of respiratory plate ‘‘C’’ shaped, surrounding bulla ( Fig. 20 ); respiratory plate with irregularly shaped holes ( Fig. 19 ); bulla prominent, wide basally, with acuminate surface.

Abdomen. Dorsal surface of segments I–VIII each with 2 transverse rows of 48 slender, long setae. Each abdominal spiracle is surrounded by 4 slender, short setae. Spiracles of abdominal segments mainly decreasing in size toward caudal side: spiracles of segments I–II 0.89–0.90 mm long, 0.78–0.80 mm wide (measured dorsoventrally); spiracles of segments III–V 0.84–0.88 mm long, 0.68–0.69 mm wide; spiracle of segment VI 0.80 mm long, 0.62 mm wide; spiracles of segments VII–VIII 0.62–0.65 mm long, 0.55–58 mm wide. Raster ( Fig. 18 ) without septula or palidia. Anal slit transversely slightly curved. Upper anal lip with large number of slender, long setae; lower anal lip with rows of setae of different size.

Remarks. Known third instar larvae of Ancognatha may be separated with the following key:

1. Epipharynx with haptomerum entire. Southwestern United States and northwestern Mexico........................................ A. manca LeConte

1 9. Epipharynx with haptomerum notched........................................ 2

2. Respiratory plates in the eight abdominal segments of similar size. Southeastern Mexico to northern Nicaragua................. A. sellata Arrow

2 9. Respiratory plates in the abdominal segments decreasing in size toward caudal end. Panama to Bolivia..................... A. scarabaeoides Erichson

Specimens examined. 59 third instar larvae hand collected in soil of potato fields from Colombia: Department of Antioquia, El Carmen de Viboral municipality, Los Garzones pathway, October–November 1995, September 1998, 2,200 m altitude, L. A. Henao, C. Restrepo and F. Vallejo (7 larvae) ; La Unión municipality, Montecristo pathway, September 1994 –1996, 2000. 2,600 m, L. A. Henao, C. Restrepo, F. Vallejo (12 larvae) ; Medellín municipality, Santa Elena, El Perico , Coltejer and Paysandú pathways, 2,550 m, August , September 1994 – 1996, 2000, L. A. Henao, C. Restrepo, F. Vallejo (10 larvae) ; Santa Rosa de Osos municipality, Llanos de Cuivá , October 1996. 2,650 m, F. Vallejo (17 larvae) . Department of Caldas, Manizales municipality, valle de Maltería, Tesorito- Universidad de Caldas farm, 2,450 m, September , October and November 2000 – 2001, F. Vallejo (5 larvae) ; Manizales department, páramo de Letras, km 28 Hwy Manizales-Bogotá Hacienda La Esperanza , 2,900 m, November 2001, F. Vallejo (4 larvae) . Department of Tolima, Fresno municipality, Herveo , Hwy Manizales- Bogotá , 3,900 m, October 2001, F. Vallejo (4 larvae) .

Pupa

( Figs. 21–23 )

Description. Total body length: 25.6 mm; maximum width: 11.5 mm. Exarate, adectic, robust oval-shaped reddish yellow.

Head. Clearly differentiated, clypeus widely trapezoidal, fused with labrum; mandibles not much defined; maxillary palp segments clearly defined; labial palps small; compound eyes and ocular canthi clearly differentiated; antennal segments thickened, bulky, with antennal club well defined.

Thorax. Pronotum widely convex, slightly longer than head, shiny. Mid-dorsal ecdysial suture well defined, beginning at anterior border of pronotum and ending between posterior edge of metanotum and basal abdominal segments. Mesothoracic respiratory spiracles rounded with prominent peritreme, 0.89 mm high and 0.82 mm wide; meso- and metathoracic respiratory spiracles not exposed. Mesonotum with wide, triangular scutellum. Metanotum with ‘‘V’’ shaped sutures easily differentiated. Elytral tecae anteriorly wide, curved to bend over dorsa of thoracic pleura, extended ventrally on wing tecae and metafemur as well as most of metatibia and part of basal abdominal segments. Meso- and metatibiae with apical spurs and lateral spines weakly defined.

Abdomen. Nine-segmented, without setae. First and second segments strongly reduced ventrally, and progresively reduced in width from segment VII to IX. Paired dioneiform structures are located between tergites I to V. Segment IX without urogomphi. Respiratory spiracles II to IV rounded, with prominent peritremes, 0.42 mm high and 0.41 mm wide. Respiratory spiracles V-VI weakly developed, probably not functional; spiracles VII–VIII atrophied, with no peritreme or pigmentation, only exposed as weakly rugose prominences. Male pupa has protarsal tecae enlarged and genital ampulla widened and prominent.

23) lateral view. Scale line 5 10 mm.

Specimens examined. 11 pupae (3 males, 8 females) from Colombia: Department of Caldas, Manizales municipality, valle de Maltería, Tesorito- Universidad de Caldas farm, 2,450 m. November and December 2000 –2001, potato field, hand collected in soil, F. Vallejo (11 pupae) .

Figures

Figs. 1–7. Ancognatha scarabaeoides. Adult. 1) male head and pronotum; 2) male antenna; 3) male fore leg; 4) female fore tarsal claws; 5) male genital capsule, distal view; 6) same, latero-ventral view; 7) same, ventral view. Scale lines 5 1 mm.

Figs. 8–13. Ancognatha scarabaeoides. Third instar larva. 8) head, frontal view; 9) epipharynx; 10) left mandible, dorsal view; 11) right mandible, dorsal view; 12) right mandible, ventral view; 13) left mandible, ventral view. Scale lines 1 mm.

Figs. 14–20. Ancognatha scarabaeoides. Third instar larva. 14) right maxilla, dorsal view; 15) left maxilla and hypopharynx, dorsal view; 16) antenna, lateral view; 17) apex of hind leg, lateral view; 18) raster; 19) detail of respiratory plate; 20) abdominal spiracle. Scale lines: Figs. 14–17 5 1 mm; Fig. 18 5 10 mm; Fig. 19 5 0.1 mm.

Figs. 21–23. Ancognatha scarabaeoides. Female pupa. 21) dorsal view; 22) ventral view;