Morphology of the larvae of Sandracottus femoralis Heller, 1934, and S. mixtus (Blanchard, 1843) and phylogenetic comparison with other known Aciliini (Coleoptera: Dytiscidae, Dytiscinae) Author Alarie, Yves School of Natural Sciences, Laurentian University, Ramsey Lake Road, Sudbury, Ontario, CANADA. Author Michat, Mariano C. 0000-0002-1962-7976 University of Buenos Aires, Faculty of Exact and Natural Sciences, Department of Biodiversity and Experimental Biology, Laboratory of Entomology, Buenos Aires, Argentina. https: // orcid. org / 0000 - 0002 - 1962 - 7976 & CONICET-University of BuenosAires, Institute of Biodiversity and Experimental and Applied Biology (IBBEA), Buenos Aires, Argentina. Naturhistorisches Museum Wien, Burgring 7, 1010 Vienna, Austria. https: // orcid. org / 0000 - 0001 - 5034 - 7342 Author Shaverdo, Helena 0000-0001-5034-7342 Author Hájek, Jiří /0000-0001-5779-154 Department of Entomology, National Museum, Cirkusová 1740, CZ- 193 00 Praha 9 - Horní Poc ̌ ernice, Czech Republic. https: // orcid. org / 0000 - 0001 - 5779 - 1542 text Zootaxa 2023 2023-04-06 5263 3 301 334 http://dx.doi.org/10.11646/zootaxa.5263.3.1 journal article 57652 10.11646/zootaxa.5263.3.1 c6b544e4-8130-404d-8b68-18fd924531fd 1175-5326 10120792 AA339050-2C93-42FC-901B-6C0CC93C7E26 Sandracottus femoralis Heller, 1934 ( Figs 1–30 ) Source of material. The three instar I, four instar II and three instar III larvae studied were associated with adults collected at the following locality: Solomon Islands , Guadalcanal : ca. 3.5 km SE of Barana village (drying up stream in shaded gorge); 09˚29.8’S, 159˚59.5’E, leg J. Hájek. The identification is safe as S. femoralis was the only Sandracottus species found in that region. Diagnosis. Larvae of S. femoralis can be distinguished from those of S. mixtus , the only other Sandracottus species described in detail, by the following combination of characters: antennomere 1 shorter than antennomere 3 (instar I) ( Figs 3–4 ; Table 1 ); antennomeres 1–2 densely covered with spinulae ( Figs 3–4 ); anterior process of prementum shorter relative to length of labial palpomere 1 ( Tables 1 , 3 , 5 ); pro- and mesofemur with less than 24 and 29 anteroventral additional natatory setae, respectively (instar I) ( Table 2 ).