The genus Liocanthydrus Guignot, 1957 (Coleoptera, Noteridae) in Argentina: new records and larval morphology

The genus <i>Liocanthydrus</i> Guignot, 1957 is formally reported from Argentina since its first mention in an unpublished work more than 40 years ago. A single species, <i>L.nanops</i>Baca et al., 2014, is recognised, with few records in the northeast part of the country, suggesting that these may represent the southern distributional limit for the genus. The habitat, a floodplain stream in the southern Atlantic Forest, is described, where both adults and larvae were collected, as well as co-occurring taxa. The first- and third-instar larvae of <i>L.nanops</i> are described for the first time. The first instar, which was unknown for the genus, gives the chance to document its primary chaetotaxy in detail. This species presents two posterodorsal projections on the abdominal segment VIII, which represent elongations of the membranous posterolateral areas of segment VIII, where setae AB8 and AB14 are usually inserted; these two setae accompany the elongation of these regions and are therefore inserted on the projections. The projections are shared with the previously described larvae of <i>L.clayae</i> (J. Balfour-Browne, 1969) but not with those of other noterid genera, and, thus, supports this unique feature as diagnostic of <i>Liocanthydrus</i>.