Coelometopon Janssens, 1972

Perkins, Philip D., 2005, A revision of the African hygropetric genus Coelometopon Janssens, and description of Oomtelecopon new genus (Coleoptera: Hydraenidae), Zootaxa 949 (1), pp. 1-103 : 1-103

Coelometopon Janssens, 1972

Coelometopon Janssens, 1972: 386 (type species Coelometopon leleupi Janssens, 1972 )

Diagnosis. Recognized by the combination of the elevated eyes, the concave frons, the prominent gular ridges, the widened eighth elytral interval (pseudoepipleuron), the coarsely sculptured dorsum, the spinose last tergite of females, and the ventral plastron.

Description. Body size ca. 2.00 to 4.00 mm, form oblong, transversely convex. Antennomeres 11 (6 + 5); 1st and 2nd elongate, subequal in length; 3rd to 6th very small; club articles tightly joined. Eyes large and elevated above concave frons. Frontoclypeal suture deep in middle, obsolete laterally where cuticle thickened, often strongly granulate in front of eye. Anterior margin of clypeus usually straight, infrequently with anterior angles slightly produced. Labrum variable, often sexually dimorphic. Maxillary palpus short, shorter than antennae, length ratios of last three palpomeres variable, often subequal or with penultimate slightly shorter, never greatly dissimilar in length; width variable, often subequal. Mentum widest subbasally, with single median or pair of depressions, anterior margin slightly produced in middle. Genae strongly produced as ridges that interlock with anterior margin of prosternum; laterally genae with distinct sulcus for reception of antenna.

Dorsum markedly granulate, each granule usually with prominent seta. Pronotum with well developed lateral depressions delimited medially by foveae; disc variable, usually with median groove bordered by pair of anterior and posterior foveae; hyaline borders absent; anterior margin markely emarginate to receive posterior margin of eyes; lateral margins strongly granulate; posterior margin often slightly produced in middle.

Elytra with 9th and 10th rows apparent only anteriorly, merged to form one row for most of length, margin of elytron (in dorsal aspect) formed by prominent granules on raised 8th interval (pseudoepipleuron). Serial punctures each with granule at anterior margin, granule bearing a short bifurcate seta; granules sometimes elongate and separating serial punctures. Even numbered intervals with granule distribution variable. Legs strongly built; without apparent sexual dimorphism; tarsi 5­5­5; claws simple.

Prosternum with procoxae separated by intercoxal process, process widened behind, closing procoxal cavities; prosternum anterior to coxae flat or with weak median carina. Mesosternum with very small to moderate protuberance between mesocoxae. Metasternum with discal depression; arcuate carina behind each mesocoxa, laterally with large punctures. Abdomen strongly sclerotized, deeply grooved between ventrites; intercoxal sternite triangular, posterior margin and contiguous area of first sternite conjointly depressed. Females with fringe of strong spines on last tergite.

Antennal pocket (terminology as in Perkins 1997) large and deep, narrowly opened ventrally, dorsally opened at well­developed postocular emarginations; short, raised ridge or carina present in pocket, on internal face of hypomeron; pocket hydrofuge pubescent in narrow band along medial margin, and more extensively so at dorsomedial area, otherwise pocket smooth and with very sparse exocrine pores. Hypomeral carina distinct, angulate just before posterolateral angles; anteriorly becoming obsolete at antennal pocket. Bubble­hypomeron becomes increasingly narrow anteriorly, very narrow at constricted entrance to antennal pocket, where anteromedial angle of wet­hypomeron is produced. Wet­hypomeron very wide in anterior 2/3, much narrower posteriorly, reticulate, almost lacking exocrine pores. Randomly distributed over anterior 1/4 are about 12–16 hypomeral setae that are long and flexible, not basally widened; interspersed with these setae are much shorter, stout, arcuate setae similar to those on lateral margin. Hypomeral antennal pocket setae, about 12–15 in number, are located along margin of antennal pocket. There are no organized clusters of exocrine pores or end­apparatus, and no secretion sulcus exists on hypomeron. Periocular exocrine pores are present. A sparse line of pores is present submarginally along occipital carina. Subocular antennal groove deep, medial margin cariniform; a few exocrine pores present in groove and along its lateral margin; groove smooth except small spiculate area at posterolateral extreme (i.e., ventromedial extreme of postocular area). Large postocular area clothed in hydrofuge pubescence, but lacking any specialized exocrine secretion delivery setae or sensilla. There appear to be no antennal cleaning structures in pocket or on prosternum.