Peltochares Régimbart, 1907

Minoshima, Yûsuke N., Fikáček, Martin & Liu, Hsing-Che, 2023, Larval morphology of Crephelochares and Peltochares (Coleoptera: Hydrophilidae), Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) 63 (2), pp. 305-322 : 311-312

Peltochares Régimbart, 1907

Diagnosis. Nasale with distinct teeth, almost symmetrical ( Fig. 9B ). Epistomal lobes present, rounded, almost symmetrical ( Fig. 9B ). Frontal lines convergent at base, coronal line short ( Fig. 6A ). Head capsule and head appendages with paddle-shaped setae ( Figs 6–7 ). Antennomere 1 with small subapical projection on inner face ( Fig. 10A ). Antennal sensorium SE1 present on intersegmental membrane between antennomeres 1 and 2 ( Fig. 10A ). Mandibles symmetrical, with two inner teeth ( Figs 7D–E , 10B ). Anterior corners of mentum projecting anteriorly, this projection sharply pointed in first instar ( Fig. 7F ), rounded in second and third instar ( Figs 8F , 10F ). Legs well developed ( Fig. 9F ). Dorsal part of posterior margin of segment 8 strongly projected posteriorly, forming trilobate projection ( Fig. 9G ). Abdominal prolegs absent. Acrocercus long ( Fig. 9G ).

Comparative notes. Larvae of Peltochares are similar to those of Helochares Mulsant, 1844 ; however, Peltochares may be distinguished from Helochares by the anteriorly projecting corners of mentum ( Figs 7F , 8F , 10F ); anterolateral corners are angulate and not projecting anteriad in Helochares (e.g., ARCHANGELSKY 1997, MINOSHIMA & HAYASHI 2011) ( Table 2). In this character, Peltochares resembles representatives of the tribe Hydrophilini and the genus Amphiops Erichson, 1843 of the subfamily Hydrophilinae . The larva of Peltochares differs from that of Amphiops by the presence of ligula, narrower mentum, very short maxillary palpomere 1, and antennomere 1 much shorter than antennomere 2 (see MINOSHIMA & HAYASHI 2012). It differs from the larvae of Hydrophilini in the well-developed antennal sensorium (reduced in size and hence inconspicuous in all Hydrophilini larvae), the very short maxillary palpomere 1, and antennomere 1 without numerous setae or spines (see e.g., ARCHANGELSKY 1997, TORRES et al. 2008, MINOSHIMA & HAYASHI 2011).

Figures

Fig. 9. Third instar larva of Peltochares atropiceus (Régimbart, 1903). A – head, dorsal view; B – anterior margin of head capsule; C – head capsule, dorsal view; D – head capsule, ventral view; E – prosternum, ventral view; F – prothoracic leg; G – spiracular atrium, dorsal view.

Fig. 6. Head capsule of first instar larva of Peltochares atropiceus (Régimbart, 1903). A – dorsal view; B – ventral view; C – detail of anterior margin, dorsal view.

Fig. 10. Head appendages of third instar larva of Peltochares atropiceus (Régimbart, 1903). A – antenna, dorsal view; B – mandible, dorsal view; C, D – maxilla, dorsal view (D) and ventral view (E); E, F – labium, dorsal view (F) and ventral view (G).

Fig. 7. Head appendages of first instar larva of Peltochares atropiceus (Régimbart, 1903). A – antenna, dorsal view; B, C – mandibles, dorsal view; D, E – maxilla, dorsal view (D) and ventral view (E); F, G – labium, dorsal view (F) and ventral view (G).

Fig. 8. Head appendages of second instar larva of Peltochares atropiceus (Régimbart, 1903). A – antenna, dorsal view; B – mandible, dorsal view; C, D – maxilla, dorsal view (D) and ventral view (E); E, F – labium, dorsal view (F) and ventral view (G).