Pneuminion Perkins, 1997

Perkins, Philip D., 2004, A revision of the South African endemic water beetle genus Pneuminion Perkins (Coleoptera: Hydraenidae), Zootaxa 538, pp. 1-38 : 4-5

Pneuminion Perkins, 1997

Pneuminion Perkins, 1997: 171 (type species Pneuminion velamen Perkins, 1997 )

Diagnosis. Recognized by the combination of the transverse, non­cordiform pronotum lacking hyaline margins and with well­developed postocular emarginations, the elytra with ten very regular series of punctures and all interseries equally developed (except P. i m p re s ­ sum), the 11 articles of the antenna (six + club), the ocelli located midway between the midline and the eyes, the moderately short maxillary palpi with length ratios of last three articles as five:four:eight, the restricted abdominal hydrofuge pubescence, the very large wet­hypomeron, and the features of the postocular/hypomeral antennal pocket (see below).

Description. Body size ca. 1.30 mm to 2.00 mm, form elongate oval, moderately convex dorsally, head not deflexed. Antennomeres 11 (six + club), third slightly longer than combined lengths of fourth to sixth. Maxillary palpi moderately short, length ratios of articles two to four (last) as five: four: eight. Eyes well­developed, not elevated. Labrum large, set at angle to clypeus, apicomedially deeply incised; anterior margin fringed with long setae. Clypeus anterior margin straight. Ocelli located midway between midline and eyes, frons very weakly convex between ocelli; area behind and between ocelli lacking carinae.

Pronotum with anterior midlongitudinal fovea, behind which is U­shaped fovea; lateral depressions not demarked by foveae; lateral margin arcuate. Hyaline borders absent; setal fringe on base in front of scutellum. Elytra usually with ten rows of punctures. Prosternum in front of procoxae shorter than procoxal cavities, latter open behind ( Fig. 8 ). Metasternum with shallow midlongitudinal impression. Intercoxal sternite small, triangular. Legs moderately elongate, tarsi five­five­five. Abdominal sterna one­four about equal in length, fifth slightly longer than fourth; in male, seventh concealed beneath sixth; in female seventh visible beyond posterior margin of sixth; first and basal part of second hydrofuge pubescent, remainder with sparse, fine, long setae. Hydrofuge pubescence also present on postocular area, bubble­hypomeron (except antennal pockets), notal postcoxal projections, mesosternum, and metasternum.

Antennal pocket (terminology as in Perkins, 1997) located in anterior face of prothorax, moderately deep, opened ventromedially (between hap­setae and the prosternum) and dorsally (at postocular emarginations); middle portion of antennal pocket convex, partially dividing pocket into dorsal and ventral concavity. About nine exocrine pores located along the medial margin of pocket, next to notosternal suture; otherwise pocket has very few, randomly distributed exocrine pores.

Hypomeral carina well defined, angulate posteriorly and becoming obsolete anteriorly at the antennal pocket. Bubble­hypomeron narrow and very sparsely pubescent opposite notosternal suture. Wet­hypomeron very wide, slightly wider anteriorly than posteriorly, reticulate, non­setose (except hap­setae) and with very sparse randomly distributed exocrine pores. Row of 12–15 well­developed hypomeral antennal pocket setae located along the ventral margin of antennal pocket; setae closely spaced, each widest in middle, tapering apically, and flattened; setae becoming progressively longer from most lateral to most medial, latter arising from anterior extreme of hydrofuge hypomeron, adjacent to lateral extreme of procoxal cavity. There are no organized clusters of exocrine pores or endapparatus, and no secretion sulcus exists on the hypomeron.

A dense cluster of sharp spines, the prosternal antennal cleaner, is located on anterolateral margin of prosternum. The antennal cleaner is surrounded by sparsely pubescent asperite hydrofuge.

Periocular exocrine pores are present along subocular antennal groove and at posterior margin of eye; medial margin of antennal groove raised slightly, not cariniform; few exocrine pores located near posteroventral angle of eye; well­developed postocular ridge delimits postocular and subocular areas; postocular area clothed in hydrofuge pubescence, but lacks any specialized exocrine secretion delivery setae or sensilla.

Figures

FIGURE 8. Pneuminion semisulcatum holotype. Ventral habitus.