Aphodius (Bodilus) ictericus (Laicharting, 1781)

Frolov, Andrey V., Vishnevskaya, Maria S. & Akhmetova, Lilia A., 2021, Identification of larvae of two Aphodius Helwig, 1798 (Coleoptera: Scarabaeidae: Aphodiinae) species using morphology and DNA barcode, Zootaxa 5047 (2), pp. 153-164 : 158-162

Aphodius (Bodilus) ictericus (Laicharting, 1781)

Figs. 22–45

Material examined. More than a hundred of the third instar larvae were collected on 7.–9.XI. 2019 in cow dung near Dosang and Topal settlements (Astrakhan Province, south of the European part of Russia). All larvae were about the same size and similar exteriorly. Thirty live larvae were taken to the ZIN laboratory and in two months 13 adults were obtained. For two adults and three larvae DNA barcodes were obtained (Genbank accession numbers: MW 672587 – MW 672591 , voucher numbers: COI121905, COI121906, COI121908, COI121921, COI121922) .

Description of the third instar larva. Larva of typical C-shape form, relatively slender, covered with sparse, short setae, with whitish, semitransparent integument except for head.

Head width: 1.51± 0.04 mm, length (without labrum): 1.13± 0.03 mm. Head surface shiny, smooth ( Figs 33, 34 ). Color pattern of head capsule varies from light brown with unclear lighter spots to dark-brown pleural sclerites with distinct lighter spots and brown frons ( Figs 22–25 ). Frontal sutures are visible as very fine, darker lines.

Epicranial suture approximately 4 times shorter than frons height. Each pleural sclerite of epicranuim with 5 long setae: 4 near antennal support and 1 near epicranial suture. A few shorter setae located on pleural sclerite are arranged in irregular rows. Frons with 2 pairs of long setae and 3 pairs of short setae. Stemmata absent. Clypeus trapezoidal, brown. Postclypeus (2/3 length of clypeus) darker than preclypeus. Surface of clypeus without prominent tubercles. First 3 proximal antennomeres about same length, antennomere 1 with whitish stripe, antennomere 3 with small conical process and 5 minute setae distally. Ultimate antennomere short and conical, with 1 smooth elongated sensory area medially near apex and small apical area with a few basiconic sensilla and 1 minute seta.

Labrum ( Figs 37–39 ) trilobed apically, with a pair of long setae and 1–2 pairs of short setae dorsally, 24 setae on anterior and lateral margins, and a pair of short robust setae ventrobasally. Clithra present, symmetrical. Phoba (protophoba, dexiophoba, and laeophoba sensu Ritcher (1966)), as a semicircular ridge of inclinate mediad and sclerotized apically spinules; most spinules pectinate apically. Short additional ridge situated anteriorly on right side. Phoba anteriorly flanked with a row of ca. 20 placoid sensilla; 2 larger placoid sensilla between clithra. Epitorma long, parallel-sided, rounded and slightly widened apically. Pternotormae developed, subsymmetrical.

Mandibles ( Figs 40–43 ) triangular, asymmetrical, external sides with 3 setae. Left mandible slightly longer than right mandible, its scissorial part wider, S 1 and S 2 teeth widely separated by sinuation, S 2 and S 3 close, separated by incision. Right mandible: S 1 and S 2 teeth fused, S 3 separated from them by incision. Base of mandible light brown, scissorial and molar part dark black.

Maxillae symmetrical ( Fig. 36 , 44, 45 ). Cardo with 4 short setae: 2 on ventral side and 2 on lateral margin near base of stipes. Ventral side of stipes with 1 long proximal and 2 short distal setae, dorsal side with a row of 8 stridulatory teeth and 3 setae near base of palpifer (2 longer setae and 1 minute seta). Palpifer without stridulatory teeth, with one short seta ventrally. Maxillary palpus with 4 palpomeres; palpomeres 1 and 4 with 1 seta each, palpomeres 3 with 2 setae; seta in 1st palpomere modified ( Fig. 36 , arrowed). Ventral side of galea with longitudinal row of 9–10 short setae. Dorsal side and apex of galea with 6 longer setae. Dorsal side of lacinia with 5 long and thick setae and 1 shorter and slenderer seta basally, ventral side with 1 short seta basally. Uncus of lacinia tridentate, with 1 thick seta basad of the apical teeth.

Postmentum with 2 pairs of short setae. Proximal part of prementum with a pair of long setae. Distal part of prementum with a pair of long setae. Glossa surrounded laterally by rows of thick and ling setae reaching submentum ventroapically; distal setae long and acute, proximal setae shorter and somewhat spatulate, specifically in right row. Glossa with 3 pairs of setae apically, 2 pairs of larger placoid sensilla, a transverse row of ca. 20 smaller placoid sensilla proximad of larger sensilla, and a row of short, triangular spinules immediately proximad of row of placoid sensilla.

Middle and hind legs of subequal length, fore legs slightly shorter. Each leg with 36 setae: 3 on coxa, 7 on trochanter, 11 on femur, 13 on tibia, and 2 on tarsus. Tarsal apices not serrate in lateral view, leg segments without tubercles.

Thoracic and abdominal segments with short and sparse setae. Folds of abdominal tergites 1–6 with shorter, thick setae arranged in transverse rows medially; setae not situated on conical tubercles. Lateral bulges of abdominal segments with 2 setae. Protoracic spiracles about 2 times larger than abdominal spiracles; abdominal spiracles of subequal size, minute.

Raster without pallidia, with 56–60 relatively long, strongly sclerotized spinules. Medial spinules robuster and slightly flattened and widened apically ( Fig. 35 ). Spinules are not arranged in rows or, in some specimens, medial spinules appear to be arranged in irregular longitudinal rows ( Figs. 26–31 ). Lower anal lobe not sinuate laterally ( Fig. 32 ).

Diagnosis. The Krell’s (1997) key to Central European Aphodius larvae includes the larva of this species, however it is characterized as having a distinct smooth area of the raster which reaches middle of the raster. Examination of our material shows that this character is not reliable and the smooth area is unclear in most specimens examined. The third instar larvae of A. (B.) ictericus is better diagnosed by having a smooth, shiny head with width ca. 1.5 mm and a characteristic color pattern of the pleural sclerites, raster with ca. 50–60 spinules without distinct pallidia and with unclear or indistinct smooth area basally, and by the modified setae on the first maxillary palpomere. The latter character, however, needs further examination because the larvae of few species of Aphodius were studied with SEM.

Figures

FIGURE 36. Aphodius (B.) ictericus, third instar larva, labio-maxillary complex, SEM, dorsal view (above) and ventral view (below).

FIGURES 22–35. Aphodius (B.) ictericus, third instar larva. 22–25, 33, head; 26–31, anal sternite; 32, anal segment, caudal view; 34, head sculpture at high magnification; 35, spinules of raster. Figures 33–35, SEM.

FIGURES 37–45. Aphodius (B.) ictericus, third instar larva. 37–39, labrum in dorsal (37) and ventral (38, 39[SEM]) view; 40–41, left mandible in dorsal (40) and ventral (41) view; 42–43, right mandible in dorsal (42) and ventral (43) view; 44–45, labio-maxillary complex in dorsal (44) and ventral (45) view.