Results DESCRIPTION OF IMMATURE STAGES. Three instar larva. Body white, body length 8 mm, maximal width 0.9 mm. Body shape cylindrical, tapering anteriorly, truncate posteriorly with 2 posterior spiracles on short spiracular tubes (Figs 4–6). Creeping welts are weakly developed with transparant spinules. Anterior spiracles fan-like with 15–16 papillae (Fig. 7). Cephalopharyngeal skeleton strongly sclerotized (Fig. 9). Mandibles massive with long hook and small tooth basally (Fig. 8). Dentate sclerite curved. Parastomal bar narrow. Hypopharynx 3 times as long as wide. Tentorial phragma broad, dorsal cornua of pharyngeal sclerite shorter than the ventral. Dorsal cornua of pharyngeal sclerite relatively narrow with very long and slit-like dorsal window. Ventral cornua with small triangular window. Body integument white, smooth. Abdominal creeping welts weakly developed and consist of transparant spinules except those in front of perianal pad — there are 4 irregular rows of spinules each is formed by 22–28 black spinules. Terminal segment of the body with two white short respiratory tubes, distance between the posterior spiracles is equal to 0.75–1.0 of the width of the spiracle (Figs 5, 6). Spiracular plates brownish, each with three identical radial spiracular openings (Fig. 10). Anal plate transverse, oval, 0.5 times as long as wide. Anus is situated in a longitudinal cleft. Puparium. Brown, body length 5.0– 5.5 mm, maximal width 1.8–2.0 mm. Body shape cylindrical, slightly more convex on the dorsal side, tapering and bilobed anteriorly (Figs 11, 12). Brown, integument in minute folds on the dorsal side and a few rows of spinules on the ventral side of abdominal segments. Anterior spiracles fan-like with 15–16 papillae (Fig. 15). Cephalopharyngeal skeleton as in three instar larva (Fig. 9). Body integument brown. Abdominal creeping welts weakly developed and consist of 3–4 rows of minute spinules. Terminal segment of the body with weekly developed tubercles, subanal pair and unpaired postanal tubercle are the longest, with two short respiratory tubes, distance between them 0.75 as wide as the tube (Fig. 14). Spiracular plates brownish, each with three identical radial spiracular openings (Fig. 10). Anal plate brown, transverse, oval, 0.5 times as long as wide. Anus is situated in a longitudinal cleft (Fig. 14).

Published as part of Ozerov, A. L. & Krivosheina, M. G., 2025, To the biology of Suillia flavifrons (Zetterstedt, 1838) (Diptera: Heleomyzidae) with a description of the immature stages, pp. 130-135 in Russian Entomological Journal 34 (1) on pages 133-134, DOI: 10.15298/rusentj.34.1.16, http://zenodo.org/record/16967467