Laccobiini

Minoshima, Yûsuke N., Iwata, Yasuyuki, Fikáček, Martin & Hayashi, Masakazu, 2017, Description of immature stages of Laccobius kunashiricus, with a key to genera of the Laccobiini based on larval characters (Coleoptera: Hydrophilidae), Acta Entomologica Musei Nationalis Pragae 57 (1), pp. 97-119 : 114-116

Key to the known genera of the tribe Laccobiini

The tribe Laccobiini contains 11 genera ( SHORT & FIKÁČEK 2013), of which the larval morphology has been described in detail and based on reliably identified specimens for five genera ( Laccobius , Oocyclus , Paracymus Thomson, 1867 , Tormus Sharp, 1884 , and Tritonus Mulsant, 1844 ) (e.g., BØVING & HENRIKSEN 1938; ARCHANGELSKY 1997; ARCHAN- GELSKY & FIKÁČEK 2004; FIKÁČEK et al. 2013, 2017). The larva of Pelthydrus Orchymont, 1919 was mentioned by BERTRAND (1936, 1974): it was first described as ʻHydrophilidae genus 1ʼ and only later assigned to Pelthydrus . Since the description of the larva is very incomplete and the identification seems doubtful ( MINOSHIMA & HAYASHI 2011), we are not including this larva into the key below. Larvae are not known for Afrotormus Hansen, 1999 , Arabhydrus Hebauer, 1997 , Hydrophilomima Hansen & Schödl, 1997 , Ophthalmocyclus Komarek, 2003 and Scoliopsis Orchymont, 1919 . Based on the phylogenetic position of these genera ( SHORT & FIKÁČEK 2013, TOUSSAINT et al. 2016), we suppose that the larva of Ophthalmocyclus may be similar to that of Oocyclus , and the larva of Scoliopsis to that of Tritonus . Genera Pelthydrus , Arabhydrus and Hydrophilomima form a large separate clade within the Laccobiini whose larval morphology remains totally unknown. The larvae of Oriental species of Oocyclus are unknown and may not necessarily correspond with larvae of Neotropical Oocyclus , since Oriental Oocyclus seem phylogenetically closer to Pelthydrus + Arabhydrus + Hydrophilomima .

1 Both mandibles similar in shape and with same number of inner teeth (e.g., Figs 11C, D in FIKÁČEK et al. 2013). .................................................................................................... 2

– Mandibles distinctly asymmetrical, with different number of inner teeth on each mandible; left mandible with fine combs on the base of the basal inner tooth ( Figs 5C, D , 10C, D ). .................................................................................................................................... 4

2 Frontal lines V-shaped, convergent posteriorly ( Fig. 3A in FIKÁČEK et al. 2017); coronal line present; sensorium SE1 small ( Figs 5B , 6A in FIKÁČEK et al. 2017); endemic to Madagascar and Seychelles. .............................................................. Tritonus Mulsant, 1844

– Frontal lines parallel or oblique, not convergent posteriorly ( Fig. 2 in ARCHANGELSKY 1999, Fig. 14A in FIKÁČEK et al. 2013); coronal line absent; sensorium SE1 long, as long as antennomere 3 (e.g., Fig. 5 in ARCHANGELSKY 1999 and Figs 11A , 13A, 15A in FIKÁČEK et al. 2013)........................................................................................................................ 3

3 Frontal lines lyriform, almost parallel (Fig 34C in ARCHANGELSKY 1997, Fig. 2 in ARCHAN- GELSKY 1999); maxilla and mentum bearing sparsely arranged short cuticular spines (Figs 35D, E in ARCHANGELSKY 1997, Figs 6 , 8 in ARCHANGELSKY 1999); labium not bearing densely arranged long hair-like projections (Fig. 35D in ARCHANGELSKY 1997, Fig. 8 in ARCHANGELSKY 1999); ligula present (Fig. 35D in ARCHANGELSKY 1997, Fig. 8 in ARCHAN- GELSKY 1999). ........................................................................ Paracymus Thomson, 1867

– Frontal lines almost straight, oblique ( Figs 10A , 14A in FIKÁČEK et al. 2013); maxilla and labium bearing densely arranged hair-like cuticular projections (e.g., Figs 11E, G , 15E, G in FIKÁČEK et al. 2013); labiumligula absent ( Figs 11G , 13G, 15G in FIKÁČEK et al. 2013); endemic to New Zealand. ................................................................. Tormus Sharp, 1884

4 Frontal lines parallel, almost straight ( Fig. 3A ); larger mesonotal sclerites rather small, separate medially ( Figs 2 , 7C ). ................................................ Laccobius Erichson, 1837

– Frontal lines lyriform (Fig. 47B in ARCHANGELSKY 1997); larger mesonotal sclerites large, attached medially, finely divided by sagittal line. ......................... Oocyclus Sharp, 1882

Figures

Fig. 11. Mesothoracic leg of Laccobius kunashiricus Shatrovskiy, 1984. First (A) and third (B) instar larva, anterior view.

Fig. 5. First instar larva of Laccobius kunashiricus Shatrovskiy, 1984, head appendages.A–B – antenna, dorsal (A) and ventral (B) view; C–D – mandible, dorsal view; E–F – maxilla, dorsal (E) and ventral (F) view; G–H – labium, dorsal (G) and ventral (H) view. Asterisk (*) in the scale bar means same scale.

Fig. 10. Third instar larva of Laccobius kunashiricus Shatrovskiy, 1984, head appendages.A–B – antenna, dorsal (A) and ventral (B) view; C–D – mandible, dorsal view; E–F – maxilla, dorsal (E) and ventral (F) view; G–H – labium, dorsal (G) and ventral (H) view.

Fig. 3. First instar larva of Laccobius kunashiricus Shatrovskiy, 1984, head capsule, dorsal (A) and ventral (B) view.

Fig. 6. Second instar larva of Laccobius kunashiricus Shatrovskiy, 1984, head appendages. A–B – antenna, dorsal (A) and ventral (B) view; C–D – maxilla, dorsal (C) and ventral (D) view.

Fig. 2.Laccobius kunashiricus Shatrovskiy, 1984.A – third instar larva; B – feeding behaviour of larva; C–D – pupa in pupal chamber.

Fig. 8. Third instar larva of Laccobius kunashiricus Shatrovskiy, 1984, head capsule, dorsal (A) and ventral (B) view.

Fig. 7. Third instar larva of Laccobius kunashiricus Shatrovskiy, 1984.A – head, dorsal view; B – prosternal sclerite, ventral view; C – mesonotal sclerites, dorsal view; D – spiracular atrium, dorsal view.