Aphodius (Alocoderus) hydrochaeris (Fabricius, 1798)

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 : 154-158

Aphodius (Alocoderus) hydrochaeris (Fabricius, 1798)

Figs. 1–21

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 11 adults were obtained. For two adults and one larva the DNA barcodes were obtained (Genbank accession numbers: MW 672592 – MW 672594 , voucher numbers: COI121912, COI121919, COI121920) .

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: 2.0± 0.05 mm, length (without labrum): 1.43± 0.05 mm. Head capsule color varies from dark-brown with paler base and apex of frons and area around antennal support ( Fig. 1 ) to brown with unclear darker pattern of epicranium ( Fig. 4 ) with intermediate variants ( Figs 2, 3 ). Head surface dull, microreticulate ( Figs 9, 11 ). 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 (3/4 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 13–15 ) 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 16–19 ) 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 ( Figs 12 , 20, 21 ). 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 13–14 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, palpomere 3 with 2 setae. Ventral side of galea with longitudinal row of 9 short setae. Dorsal side and apex of galea with 6 longer setae. Dorsal side of lacinia with 5 long and thick setae and 3 shorter and slenderer setae basally, ventral side with 1 short seta basally. Uncus of lacinia tridentate, with 1 or 2 thick setae basad of the apical teeth.

Postmentum with 2 pairs of short seta. Proximal part of prementum with a pair of long setae. Distal part of prementum with 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 3 setae. Protoracic spiracles about 2 times larger than abdominal spiracles; abdominal spiracles of subequal size, minute.

Raster ( Figs 6–8 ) with pallidia of 8-11 relatively long, strongly sclerotized, depressed spinules ( Fig. 10 ); pallidia curved and converge towards basal margin of sternite. Anal sternite also bears smaller spinules on each side of pallidia. Lower anal lobe not sinuate laterally ( Fig. 5 ).

Diagnosis. The larva of A. (A.) hydroсhaeris was described by Martynov (1999), however the differential diagnosis was not provided and specifically the chaetotaxy of the maxilla was not described. In the key to Aphodius larvae ( Krell 1997) this species comes out in the couplet with A. (Melinopterus) prodromus (Brahm, 1790) but differs from it in the larger head size, the absence of the red hue in the head capsule coloration, and setation of the lacinia having five longer and thicker setae and three shorter and slenderer ones basally.

Figures

FIGURE 12. Aphodius (A.) hydrochaeris, third instar larva, labio-maxillary complex, SEM, dorsal view (above) and ventral view (below).

FIGURES 1–11. Aphodius (A.) hydrochaeris, third instar larva. 1–4, 9, head; 5, anal segment, caudal view; 6–8, anal sternite; 10, spinules of raster; 11, head sculpture at high magnification. Figures 9–11, SEM.

FIGURES 13–21. Aphodius (A.) hydrochaeris, third instar larva. 13–15, labrum in dorsal (13) and ventral (14, 15[SEM]) view; 16–17, left mandible in dorsal (16) and ventral (17) view; 18–19, right mandible in dorsal (18) and ventral (19) view; 20–21, labio-maxillary complex in dorsal (20) and ventral (21) view.