Merodon aureus Fabricius, 1805

Preradović, Jelena, Andrić, Andrijana, Radenković, Snežana, Zorić, Ljiljana Šašić, Pérez-Bañón, Celeste, Campoy, Andrés & Vujić, Ante, 2018, Pupal stages of three species of the phytophagous genus Merodon Meigen (Diptera: Syrphidae), Zootaxa 4420 (2), pp. 229-242 : 232-233

Merodon aureus Fabricius

Puparium description. Dimensions and shape. Length: 7.5 mm, width: 3.5 mm, height: 3 mm; sub-cylindrical; anterior end truncate, tapering posteriorly and flattened Ventrally; cream to light brown in colour; rough integument with larVal segmentation persisting as transVerse folds and wrinkles.

Cephalopharyngeal skeleton. Robust mandibles with black sclerotised hooks and blunt apex, without accessory teeth, fused to the external mandibular lobes; the mouth hooks separated at the apex by about the same distance as their basal width; the dorsal cornu narrowed towards the apex, shark’s fin shaped, representing almost the whole length of the Ventral cornu; clipeal sclerite and tentorium highly sclerotised and apparently fused to the intermediate sclerites; Ventral cornu elongated and narrow in profile View, with the cibarium located at the base ( Fig. 1A ).

Pupal spiracles. Sclerotised, blackish-brown in colour, cylindrical in shape, gradually tapering and pointed at the end; 0.6 mm long; separated by a distance of 4× their length; apex with a granular surface; surface of the base smooth or slightly rough; each spiracle bearing numerous irregularly-spaced domed tubercles ( Fig. 2A ) except for the pointed apex; surface between tubercles smooth or slightly rough; tubercles composed of two layers; 4–7 radially-arranged spiracular openings on each tubercle ( Fig. 2B ).

Prp. Reddish-brown and shiny, sub-elliptical in cross-section, short (Visible from dorsal View) and wider than long; with an annular grooVe at the base and another just before the spiracular plate; surface between the two grooVes ornamented with a network of small rounded protuberances ( Fig. 3A ); the outline of the spiracular plate irregular with indentations at the locations of the inter-spiracular setae; spiracular plate of prp with four pairs of slightly curVed and conVoluted spiracular openings around two central scars ( Fig. 3B ); the spiracular openings clearly separated from each other; four pairs of well deVeloped inter-spiracular setae emerging from the edge of the spiracular plate; each seta with at least four main branches, each of which possesses multiple sub-branches from the base to the tip of the seta ( Fig. 3C ).

Examined material. Đerdap National Park, Serbia (44° 32 ' 38"N, 22°01'08"E), leg. J. PreradoVić: 1 puparium in the ground near bulbs of Ornithogalum umbellatum, V.2013 (P 1 in FSUNS) ; 1 puparium on the ground close to O. umbellatum plants, Viii. 2015 (P 4 in FSUNS).

Biology. Males and females of M. aureus were obserVed flying near and resting on plants of Ornithogalum sp. from the beginning of May to the beginning of June in 2011 -2013 and 2015-2016 (more than 50 obserVations in total). Up to four adults were noted to sometimes rest simultaneously on the same plant leaVes. Females of M. aureus were often obserVed settling for oViposition between the base of an Ornithogalum sp. plant and the surrounding soil, behaVing as if they were laying eggs on the ground, Very close to the plant. HoweVer, we neVer found eggs. The females made intermittent buzzing sounds while maintaining their positions for oVer fiVe minutes. Thereafter, they cleaned themselVes for a few minutes before flying away.

Figures

FIGURE 1. Cephalopharyngeal skeleton of Merodon puparia, lateral view: (A) M. aureus (P4), (B) M. avidus (P2). Abbreviations: c, cibarium; cs, clipeal sclerite; dc, dorsal cornu; is, intermediate sclerite; m, mandibles; t, tentorium; vc, ventral cornu. Scale lines: A, B = 500 µm.

FIGURE 2. SEM micrographs of the pupal spiracles of Merodon puparia: (A) M. aureus (P4), (B) M. aureus (P1), (C) M. avidus (P6), (D) M. rufus; (A, C, D) Pupal spiracle, (B) Spiracular openings on a tubercle. Abbreviation: tu, tubercle. Scale lines: A, C = 200 µm; B = 5 µm; D = 50 µm.

FIGURE 3. SEM micrographs of the posterior respiratory processes (prp) of Merodon puparia: (A, B) M. aureus (P4), (C) M. aureus (P1), (D) M. avidus (P2), (E, F) M. rufus; (B, D, F) prp showing the spiracular plate, (A, E) prp in dorsal view, (C) Inter- spiracular seta. Abbreviations: cs, central scar; is, inter-spiracular seta; so, spiracular opening. Scale lines: A, D = 250 µm; B = 200 µm; C = 10 µm; E, F = 100 µm.