Cyclocephala distincta Burmeister, 1847

Souza, Thamyrys Bezerra De, Maia, Artur Campos Dália, Albuquerque, Cleide Maria Ribeiro De & Iannuzzi, Luciana, 2014, Description of Cyclocephala distincta Burmeister (Coleoptera: Scarabaeidae: Dynastinae: Cyclocephalini) immatures and identification key for third instars of some Cyclocephala species, Zootaxa 3872 (2), pp. 180-186 : 181-184

Cyclocephala distincta Burmeister, 1847

Figs. 1–18

Description of the third instar ( Fig. 2 ). Head ( Fig. 3 ). Maximum width of head capsule 2.61 ± 0.06 mm. Surface of cranium —Epicranial suture distinct , brown-colored; about half length of white-colored frontal suture. Epicranial and frontal sutures form an inverted ‘Y’. Epicranial surface with longitudinal row of 3–4 slender, dorsoepicranial setae on each side of epicranial suture; parallel to the dorsoepicranial setae a row of 5–6 setae, the apical pair five times longer than the remainder. Ocelli visible, black; 12–16 paraocellar slender setae on basis of each antenna. Frons —Each side with 2 pairs of posterior, slender, frontal setae; 2 pairs of anterior, slender, frontal setae; 2 pairs of anterior angle frontal setae; 1 slender, central seta; and 1 slender, outer seta. Clypeus —Form trapezoidal with distinct clypeofrontal suture, laterally delimited by precoila; 1 pair of slender outer setae and 1 pair of slender anterior seta. Labrum ( Fig. 4 )—Form oval, asymmetric, bilobed, with slender setae; 1 pair lateral seta, 3–4 pairs of posterior setae, 1 pair of anterior seta on each side; 7–8 apical setae. Antennae ( Fig. 5 )—With 4 antennomeres, first and second of equal length; third shorter than others, with oval, sensory spot on inner surface of apical process; fourth with 4 well-defined, oval sensory spots, 2 dorsal and 2 ventral, of equal length; apex of apical antennomere with short, slender setae.

Mandibles —Form asymmetric, subtriangular. Ventral stridulatory area with transverse striae. Left mandible ( Fig. 6–7 ) with 3 teeth in incisor area; molar area bilobed with distal lobe projecting towards proximal lobe; dorsal surface with 1 long and slender apical seta, 1 long and slender seta near the dorsal carina, and a row of 6–8 short and slender dorsomolar setae; 2–6 short and slender ventromolar setae; lateral surface with row of 5 long and slender setae; acia, in dorsal view, similar to cartilaginous tooth with 3–5 short, apical setae; brustia with 8–15 slender setae; right mandible ( Fig. 8–9 ) with 2 teeth in incisor area; dorsal surface with 1 long and slender apical seta, 1 long and slender seta near dorsal carina, and a row of 3–5 short and slender dorsomolar setae; 2 short and slender ventromolar setae; lateral surface with row of 5–6 long and slender setae; molar lobe less developed than that of left mandible; brustia with 3–6 slender setae.

Maxilla ( Fig. 10 )—With distinct suture between galea and lacinia, 1 apical, cone-shaped uncus on galea and 3 apical, conical unci on lacinia, unci fused at their bases, central smaller than others; galea with 4–8 thick setae and 6–16 slender setae; lacinia with 4–5 thick setae and 19–25 slender setae; maxillary palpi with 4 palpomeres, the apical longer than others. Lateral surface of third palpomere with 1 outer and 1 inner seta; globulous palpifer with 25–28 short, slender setae; stridulatory area with 1 anterior tubercle and a row of 6–9 truncate (1 + 6–9) teeth.

Labium. Postmentum wide, form subtrapezoidal; labial palps with 2 palpomeres each, the second longer than the first; dorsal surface of glossa with slender setae at base of second palpomere; median glossal region with scattered, short and thick setae. Hypopharynx ( Fig. 11 )—With asymmetrical, well–sclerotized hypopharingeal sclerome; right side more sclerotized than left; lateral lobe with a longitudinal row of 30–35 short, slender setae.

Epipharynx ( Fig. 12 ). Haptomeral process globose, distally formed by a tooth on left side and a rounded projection, larger than the tooth, on right side; 2–3 sensillae on basis of the tooth and 2–5 sensillae on the basis of projection; acroparia with 17–20 long slender setae; each acanthoparia with 13 short, thick setae, whose lengths decrease towards base; gymnoparia present; number of setae of chaetoparia decreases towards gymnoparia and becoming thicker near haptomeral process; right chaetoparia with 52–57 setae and left chaetoparia with 41–42 setae; pedium longer than wide; laeotorma short; pternotorma rounded; dexiotorma elongate and straight; crepis with setae and sensillae, left side larger than right; 2 nesia present. Right nesium adjacent to dexiotorma, form subtriangular; left nesium (or sensory cone) anterior to sclerotized plate and near midline of epipharynx, with 3 apical sensorial pores; longitudinal row of 7–9 slender setae below laeotorma and on left side of crepis; row of 3–5 slender setae below the dexiotorma and on left side of crepis.

Thorax. Legs setose. Tarsal claws broadened at base and elongated apically, with 1 external basal seta and 1 internal prebasal seta ( Fig. 13 ); metathoracic claws smaller than the others, mesothoracic claws smaller than prothoracic claws.

Abdomen. Raster ( Fig. 14 ) with 18–22 teges; region between basis of inferior anal labium and anal slit with 30–33 setae; barbula with more than 50 slender setae. Spiraculum ( Fig. 15 ) with “C-shaped” respiratory plate, surrounding oval-shaped bulla.

Descriptions of first and second instars. Characterizations of both first and second instars similar to that of third instar, except for the following characters:

First instar: Maximum width of head capsule 1.0 ± 0.04 mm; 7–10 paraocellar setae; right chaetoparia with 28–34 setae and left chaetoparia with 25–32 setae; 2–3 dorsomolar setae on right mandible. Raster with 10–12 teges.

Second instar: Maximum width of head capsule 1.6 ± 0.06 mm; right chaetoparia with 42–49 setae and left chaetoparia with 28–32 setae.

Description of the pupa. Body surface glabrous, largest length 12.4 ± 0.87 mm and largest width 4.4 ± 0.35 mm ( Fig. 16–17 ). Head —Hypognathous, mouthparts and antennal tecae visible; labrum and clypeus fused; ocular canthus prominent. Thorax —Wing tecae slightly longer than elytral tecae. Ecdysial suture longitudinally and dorsally defined, longitudinally extended from pronotum to second abdominal segment. Two internoapical mesotibial spurs and 2 internoapical metatibial spurs present. Abdomen —With 10 segments, only 9 clearly visible dorsally; 6 pairs of dioneiform organs distributed among segments I–II, II–III, III–IV, IV–V, V–VI, and VI–VII. Respiratory plates in segments I–II–III–IV with sclerotized and prominent peritrema. Abdominal segments IX–X smaller and narrower than the others; ventral apex of abdomen with prominent lateral margins, converging in a bilobed structure with nearly 100 slender setae ( Fig. 18 ). Sexual dimorphism defined by prominent rounded and smooth genital ampoule on last abdominal sternite and enlarged protarsi in males; genital ampoule flat in females.

Natural history. Adult C. distincta are assumed to be flower visitors of the piassava palm ( Attalea funifera Martius ex. Sprengel, Arecaceae ; Voeks 2002). Palm pollen morphotypes were also recovered from the body surfaces of specimens of C. distincta collected in light traps in Atlantic Forest remnants in the state of Pernambuco (A.C.D. Maia, personal observation). Beetles of this species can undergo their complete life cycle on an exclusively saprophagous diet for the larvae, which exhibit negative phototaxis and defecate if handled (Souza et al. personal observation).

Geographic distribution. Cyclocephala distincta was originally described from Brazil and subsequently recorded for the Guianas and Colombia. The state records for Brazil are Amazonas, Bahia, Pernambuco, Rio de Janeiro, Santa Catarina, and São Paulo ( Endrödi 1985, Maia et al. 2010).

Discussion. The larvae of C. distincta differ from those of other congenerics by presenting the smallest width of the head capsule and the largest number of setae on the right chaetoparia of the epipharynx. The form of the clypeus and labrum follows the pattern observed among most other species of the genus. The plegmatia is missing from the epipharynx (it was only described in larvae of C. testacea Burmeister ). The number of setae on the acanthoparia varies only slightly in the genus, ranging from 10–15. The number of sensory spots on the fourth antennomere of the larvae of C. distincta , and also of C. fulgurata , C. lunulata , C. gregaria Heyne & Taschenberg , C. signaticollis , C. lurida , C. celata , and C. paraguayensis Arrow is twice as that observed for the other species of Cyclocephala .

The presence of two teeth on the right mandible is only recorded in larvae of C. distincta , C. signaticollis , C. celata , and C. paraguayensis . Larvae of all other congenerics possess three teeth on the right mandible. In the maxilla, the recorded number of unci on the galea (one) and lacinia (three) of the larvae of C. distincta is similar to that observed in those of almost all other congenerics, except larvae of C. testacea , which have two unci on the lacinia.

In general, the pattern of the disposition of setae on the tarsal claws is presented as one basal, one pre–basal (1b + 1p); this pattern differs only in larvae of C. lurida (2b) and C. celata (1b + 2p). The arrangement of the setae on the raster of the larvae of C. distincta is unique within the genus. The absence of the palidia was documented for larvae of all species of Cyclocephala except those of C. testacea ( Ritcher 1966, Morelli 1991, Morelli & Alzugaray 1994, Bran et al. 2006, Lugo-García et al. 2009, Souza et al. 2013, Albuquerque et al. 2014).

The pupae of C. distincta have 2 externoapical tubercles on the protibia, a trait only shared with the pupae of C. celata ; on the other hand, the numerous slender setae on the ventral apex of the abdomen of the pupae of C. disticta also occur in four congenerics: C. fulgurata , C. signaticollis , C. gregaria , and C. testacea . However, the presence of a cone-shaped protuberance on the ventral apex of the abdomen containing setae is documented only from the pupae C. distincta and C. testacea . The number and topology of dioneiform organs in pupae of C. distincta are similar to what has been described for C. fulgurata , C. lunulata , C. gregaria , C. celata , and C. testacea ; they differ from the pupae of C. paraguayensis and C. signaticollis .

Figures

FIGURES 1 – 12. Male adult Cyclocephala distincta (1); third instar, lateral view (2); head capsule (3); labrum (4); antennal sensory spots (5); left mandible, dorsal view (6); left mandible, ventral view (7); right mandible, dorsal view (8); right mandible, ventral view (9); maxilla, ventral view (10); hypopharynx, ventral view (11); epipharynx (12).

FIGURES 13 – 15. Third instar of Cyclocephala distincta: tarsal claw of medium leg (13); raster (14); abdominal spiracle (15).

FIGURES 16 – 18. Pupa of Cyclocephala distincta: body dorsal view (16); body ventral view (17); ventral apex of last abdominal sternite (18).