Immature stages of Microdon analis Egg Fig. 1 Width = 450.71 ± 52.89 µm; length = 897.41 ± 59.72 µm (n = 10). First instar larva Figs 2−6, Supplementary Material 2 Body width = 456.23 ± 29.41 µm; body length = 900.77 ± 75.14 µm (n = 10). Body features. Body rounded anteriorly and posteriorly, but subparallel on sides. Two longitudinal grooves present dorsally (Fig. 2B), dividing dorsal body surface into three main longitudinal fields: one medial, two external marginal fields. Dorsal surface adorned with raised sculpture and showing 62 regularly spaced flower-like sensilla (Fig. 3B) distributed as follows: medial field with two longitudinal rows of nine sensilla; each marginal field with 22 sensilla. Each flower-like sensillum (Fig. 3F) composed of a long cylindrical base, apically with a medial flower-like structure with a variable number (6−7) of short lobes not exceeding the diameter of the base. Ventral surface without hairy microsculpture, showing transverse twisted protuberances (Fig. 3D). Ventral flower-like sensilla (Fig. 3H) dome-shaped, with an unsculptured simple base, without radial lobes. Pseudocephalon. Distal segment of the antenna distinctly narrowed at the apex (Figs 4B, D). Posterior sensorial organs on dorsal surface of pseudocephalon composed three short trichoid sensilla emerging from bulbous base (Fig. 4H). Posterior spiracular tubercle. Impair structure, short, bilobed. Surface of spiracular tubercle with microsculpture composed by thick, pointed, slightly imbricated scales (Figs 5B, D, F). Apex with depressed plates, laterally produced into four spikes: posterior spikes longer than the anterior (Figs 5D, F). Marginal band. Distinctly short fringe, showing 10 waves on each side (Figs 6B, D, F). Each simple process smooth both dorsally and ventrally (Figs 6B, D, F). Third instar larva Figs 7–9 Body width = 6.41 ± 0.64 mm; body length = 8.25 ± 0.54 mm (n = 10). Dorsal reticulation. Dorsal reticulation extended over the whole dorsal body surface. Each process divided into a dome-shaped basal disk supporting a branched spine (Figs 7C, D). Spines 2–branched not articulating with disk; processes disposed in 1–2 rows; trumpet-shaped tubercles (Fig. 7D) in 2–3 concentric circles on basal disk around spine base; dorsal spine branches intertwined extensively with branches originating 3–4 spines away. Dorsal flower-like sensilla with cylindrical smooth base and 3–4 lobes radiating from apex, lacking the central dome (Fig. 7D), always present at intersections of process rows and extending well above spines; each sensillum 4–5 times height of undivided spine base, 2–3 times length of processes. Posterior spiracular tubercle. Slightly wider than long structure, subrectangular both in dorsal and anterior views, concave medially (Figs 8C, D), with two round holes spaced 1.2 times as long as their diameter. Base of posterior spiracular tubercle encircled by a smooth cuticular crown. Spiracular plates flattened to slightly convex, of variable shape, separated by a broad and deep midsagittal cleft (Figs 8C, D). Marginal band. Processes on the marginal band apparently without basal articulated joints (Figs 9C, D). Puparium Figs 10, 11 Body width = 7.4 ± 0.4 mm; body length = 9.2 ± 0.3 mm (n = 10). Anterior spiracular tubercles. Length of each tubercle about three times as long as wide, subcylindrical, with sides entirely and strongly wrinkled, blunt at the apex, with the apex furrowed by about 30 respiratory fissures (Figs 10C, D). Each fissure laying on a small papilla (Fig. 10D).

Published as part of Scarparo, Giulia, Wolton, Robert, Molfini, Marco, Pinna, Luigi Cao & Ulio, Andrea Di Gi-, 2020, Comparative morphology of myrmecophilous immature stages of European Microdon species (Diptera: Syrphidae): updated identification key and new diagnostic characters, pp. 348-370 in Zootaxa 4789 (2) on pages 358-360, DOI: 10.11646/zootaxa.4789.2.2, http://zenodo.org/record/3990836