Redescription and neotype designation of Suphis fluviatilis Guignot, 1948 (Coleoptera: Dytiscoidea: Noteridae) and notes on other species of the genus.

Suphis fluviatilis Guignot, 1948 was described based on a single female specimen, and according to the author, the type was deposited in the Museum National dHistoire Naturelle (Paris, France). However, the diagnostic features of the specimen deposited under this name and provided with the respective labels deviate considerably from those given by Guignot in his original description. It is shown that this specimen belongs to Suphis notaticollis Zimmermann, 1921, confirming previous observations by Luis Grosso in 1980.

Description and chaetotaxic analysis of the larval instars of Hydrocanthus debilis Sharp, 1882 (Coleoptera: Noteridae).

All larval instars of the burrowing water beetle species Hydrocanthus debilis Sharp, 1882 are described and illustrated, including morphometric and chaetotaxic analyses of the cephalic capsule, head appendages, legs, last abdominal segment, and urogomphus. Larvae of this species have many small dark dorsal maculae on the body, which easily distinguishes it from other known species of the genus except H. socius Sahlberg, 1884.

Chaetotaxy and morphometry of the head capsule and head appendages of the genus Derallus Sharp (Coleoptera: Hydrophilidae).

The primary and secondary chaetotaxy of the head capsule and head appendages of the three larval instars of the water scavenger beetle genus Derallus Sharp are described for the first time based on two species: D. angustus Sharp and D. paranensis Oliva.

Description of immatures of Berosus decolor Knisch, 1924 (Coleoptera: Hydrophilidae: Berosini), with emphasis on chaetotaxy and morphometry.

The preimaginal stages of Berosus decolor Knisch, 1924 are described for the first time, including illustrations of the egg case and all larval instars. Larval morphology of this species is studied emphasizing chaetotaxic and morphometric analyses. The egg case lacks a mast and contains 2‒3 eggs; all larval instars are characterized by the following features: presence of 6 teeth on anterior margin of nasale; left epistomal lobe carrying 14‒16 strong and curved setae (gFR2); seta FR1 elongate, inserted posteriorly to seta PA7; pore FR14 absent; parietale with spinulae in the area between setae PA5 and PA12; mandibles asymmetrical; seta MN1 minute; first antenommere with a digitiform projection on distal inner margin; antennal sensilla AN8 and AN9 absent; maxillary sensilla MX10 hair-like, MX11 and MX16 with an intermediate shape between hair-like and spine-like; labial sensilla LA4 and LA15 absent; seta LA2 present, minute; abdomen with 7 pairs of tracheal gills.

Description of immatures of the genus Tropisternus Solier, subgenus Pristoternus Orchymont (Coleoptera: Hydrophilidae), with emphasis on the chaetotaxy and morphometry of larval forms.

The egg cases, larvae, and pupae of Tropisternus (Pristoternus) latus (Brullé, 1837), T. (P.) ovalis Castelnau, 1840, and T.