Larval chaetotaxy and morphometry of Megasternini: Cercyon (Paracercyon) Seidlitz, Cryptopleurum Mulsant and Pelosoma Mulsant (Coleoptera: Hydrophilidae) Author Rodriguez, Georgina Facultad de Ciencias Exactas y Naturales, Departamento de Biodiversidad y Biología Experimental, Universidad de Buenos Aires - Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA), CONICET-UBA, Laboratorio de Entomología, Intendente Güiraldes 2160, C 1428 EGA, Buenos Aires, Argentina. Author Archangelsky, Miguel Laboratorio de Investigaciones en Ecología y Sistemática Animal (LIESA). Centro de Investigaciones Esquel de Montaña y Estepa Patagónica (CIEMEP) (CONICET - UNPSJB), Roca 780, 9200 Esquel, Chubut, Argentina. text Zootaxa 2023 2023-07-18 5318 1 45 66 http://dx.doi.org/10.11646/zootaxa.5318.1.2 journal article 10.11646/zootaxa.5318.1.2 1175-5326 8158191 FE580DA6-5B95-4682-85F5-09376D4F13BE Cercyon analis third instar larvae Morphometry. Measurements and ratios in Table 1 . Chaetotaxy. Head capsule ( Figs. 20–22 ). Frontale usually without secondary sensilla (specimen illustrated with one secondary seta on left side near FR5–6) ( Fig. 20 ); gFR1 with eight setae. Each parietale with five secondary sensilla distributed as in second instar larvae; setae PA8, PA9, PA16 and PA21 proportionally longer than in first instar larvae. Antenna ( Fig. 23 ). Without secondary sensilla, sensory appendage (SE1) proportionally shorter than that of second instar larva. Mandibles ( Figs. 24–25 ). Each mandible with three secondary setae, distributed as in second instar larvae. Maxilla ( Figs. 26–27 ). Stipes without secondary setae, similar to that of second instar larva. Labium ( Figs. 21 , 28 ). Without secondary sensilla, LA6 proportionally longer.