Cylomissus Broun, 1903

Minoshima, Yûsuke N., Fikáček, Martin, Gunter, Nicole & Leschen, Richard A. B., 2015, Larval Morphology and Biology of the New Zealand-Chilean Genera Cylomissus Broun and Anticura Spangler (Coleoptera: Hydrophilidae: Rygmodinae), The Coleopterists Bulletin 69 (4), pp. 687-712 : 699-701

Cylomissus Broun, 1903

Diagnosis of the Larva. Table 2. Clypeolabrum ( Figs. 10C , 12C ) nearly symmetrical; nasale with two teeth in first instar, with single tooth in later instars; epistomal lobes reaching as far as or slightly further than nasale. Coronal line ( Fig. 14A ) present but very short. Head capsule of all instars ( Figs. 10A–B , 12A–B ) with numerous additional setae, those on dorsomesal portion of parietale scale-like ( Fig. 14B ). Mandibles ( Figs. 11C–D , 13C–D ) with two inner teeth each, third instar ( Fig. 13C–D ) with serrate areas on base of inner teeth. Antennal sensorium ( Fig. 11A ) ca. half as long antennomere 3. Inner face of stipes ( Figs. 11E , 13E ) with many stout spines with subapical minute tooth each, distinctly increasing in size towards distal portion; outer face of stipes of second and third instars ( Fig. 13E ) with numerous stout secondary setae; maxillary palpomere 3 long. Labium ( Figs. 11G–H , 13G–H ) moderately sized, lacking hypopharyngeal lobe; ligula present, well-sclerotized; mentum of third instar with few stout setae on distal margin; prosternum subdivided mesally. Legs ( Fig. 14D–E ) with setose ventral portion of trochanter. Abdomen ( Fig. 9B–C ) with dorsal and lateral tubercles acute at apex; dorsal sclerite of abdominal segment 8 complete ( Fig. 14F ).

As in Anticura , the larva of Cylomissus generally resembles aquatic medium-sized larvae of the tribe Hydrobiusini and may be distinguished from those by the same set of characters as mentioned under Anticura (except for unidentate nasale in second and third instars, which, however, also largely differs from all Hydrobiusini ). Differential diagnosis from larvae of New Zealand hydrophilid genera needs to be specified in the future, as larvae of several genera ( Tormissus Broun, 1893 , Saphydrus Sharp, 1884 ) also bear unidentate nasale; all other new Zealand genera have larvae with nasale bearing more than two teeth and are hence easily distinguishable from Cylomissus .

Figures

Fig. 10. Cylomissus glabratus, first instar, head capsule. A) Dorsal view, B) Ventral view, C) Anterior margin, dorsal view.

Fig. 12. Cylomissus glabratus, third instar, head capsule. A) Dorsal view, B) Ventral view, C) Anterior margin, dorsal view.

Fig. 14. Cylomissus glabratus. A) Head, third instar, dorsal view, B) detail of the superficial structure of the head capsule, third instar, C) Prosternal sclerite, first instar, ventral view, D) Mesothoracic leg, first instar, anterior view, E) Prothoracic leg, third instar, anterior view, F) Abdominal segments 8–10 with spiracular atrium, third instar, dorsal view.

Fig. 11. Cylomissus glabratus, first instar. A–B) Antenna, dorsal and ventral views, C–D) Left and right mandible, dorsal view, E–F) Maxilla, dorsal and ventral views, G–H) Labium, dorsal and ventral views.

Fig. 13. Cylomissus glabratus, third instar. A–B) Antenna, dorsal and ventral views, C–D) Left and right mandible, dorsal view, E–F) Maxilla, dorsal and ventral views, G–H) Labium, dorsal and ventral views.

Fig. 9. Cylomissus glabratus. A) First instar, dorsal view, B–D) Third instar, dorsal, lateral, and ventral views, E) Adult, F) Taranaki, Mt. Egmont National Park, Te Popo stream at Curtis Falls Track, New Zealand; M. Fikáček placing floating mosses in a plastic jar, G) Gisborne, Te Urewera National Park, Te Kumi stream at Waipai-Ruapani Track, New Zealand, H) Details of mosses at Wharekai Te Kou Walk from which Cylomissus was collected, I) Westland, Wharekai Te Kou Walk NNW of Jackson Bay, New Zealand, J) Taranaki, Mt. Egmont National Park, unnamed stream 0.2 km S of Pukeiti Garden, New Zealand, K) Westland, Mount Aspiring National Park, Mur Creek at Pleasant Flat, New Zealand, L) Detail of mosses in Mur Creek with Cylomissus. Photographs F–G and J by J. Hájek.