Description of the nymph. Body size: up to 21 mm (full grown female nymph). Coloration pattern: see Figs 7 - 8. Head. Labrum greatly expended laterally, ca 4 times larger than long, with narrow and somewhat acute apexes (Fig. 17); dorsal surface and anterior margin covered with long and thin setae; ventral surface with a long median arch of ca. 20 strong and pointed setae ending close to the anterior margin. Crown of the galea-lacinia of the maxillae composed of ca. 20 comb-shape setae, the median ones bearing 12 - 14 teeth. Right mandible (Fig. 19) with 11 - 12 fimbriate setae below the inner incisor and 5 long simple and thin setae below the mola; left mandible (Fig. 18) with 8 - 9 fimbriate setae below the inner incisor and ca. 8 - 9 long simple and thin setae below the mola. Hypopharynx with robust lingua bearing a tuft of small setae, superlinguae densely covered with long and thin setae up to the lower part of the superlinguae (Fig. 28). Labium with glossae rhomboid, clearly concave on their inner and outer margins near apex (Fig. 22), dorsal surface with numerous stout setae and numerous thin and simple setae. Thorax. Pronotum greatly expended laterally and posteriorly (Fig. 7). Femora with submarginal rows of pointed bristles on the inner and outer margins, only slightly increasing in numbers from the fore to the hind leg. Bristles on the upper face of hind femora with subparallel or slightly convergent margins, apex rounded or truncate (Fig. 33). Outer margin of hind tibia with a row of 12 - 15 pointed bristles in marginal or submarginal position (Fig. 34). Tarsal claw with 3 - 4 teeth. Abdomen. Posterolateral expansions not developed on segments I-II, moderately developed on segment III and strongly increasing in size up to VIII where they may be longer than segment IX (Fig. 9). Gill I with asymmetrical elongated and rounded plate, less than two times longer than wide (Fig. 46); gill III-VI strongly asymmetrical, wider than long (Figs 47 - 48), gill VII oval and asymmetrical with slightly pointed apex (Fig. 49). Posterior margin of tergites with long and pointed teeth regularly alternating with two small ones, and few microdenticles (Fig. 37). Cerci whitish with 3 - 4 dark brown bands increasing in size towards the apex.
Sumber: The species of Thalerosphyrus Eaton, 1881 (Insecta, Ephemeroptera, Heptageniidae, Ecdyonurinae) in Java and Sumatra, with some comments on the diversity of the genus in the Oriental Realm