Prionocerus Perty, 1831

Geiser, Michael, 2010, Studies on Prionoceridae (Coleoptera: Cleroidea). II. A revision of the genus Prionocerus Perty, 1831, Zootaxa 2328, pp. 1-48 : 3-6

Genus Prionocerus Perty, 1831

Prionocerus Perty, 1831: 33 .

Type species: P. coeruleipennis Perty, 1831 (by monotypy).

Differential diagnosis: This genus is morphologically extremely close to Idgia and the only usable character to distinguish it from this genus are the flattened, more or less strongly serrate antennae with strongly emarginate last joint, although this is also subject to some interspecific or intersex variation within Prionocerus itself, as well as within Idgia (see discussion, under "phylogeny").

From Lobonyx and some species currently placed in Idgia (which will be transferred to another genus in the future) it is easily distinguished by larger eyes, narrower and more elongate head and the absence of a clearly demarcated frontoclypeal suture, as well as the antennal shape.

Redescription: Prionoceridae of medium size, 8–14 mm in total length. Bright coloured with metallic or bright orange yellow elytra, never with black apical macula like in many Idgia species. All but one species ( P. viridiflavus ) with reddish pronotum, rarely with discal spot(s).

Head elongate, always dark coloured, behind eyes with some very long laterally projecting black bristles. Eyes very large, strongly emarginate at the sides near the antennal insertion; larger in males than in females. Frons between eyes narrow in males, broader in females; distinctly depressed and slightly rugose in front of the eyes; laterally delimited by two conspicuous sharp ridges above the antennal insertions. Clypeus slightly convex, separated from frons by a broad, deep furrow, but without any trace of a suture. Terminal segment of maxillary palpi always almost securiform and as long as or longer than the first segment. The second segment about half as long as the first. Labial palpi with very small first segment, about three times longer than second segment and subsecuriform terminal segment of about the same length as the second, but much larger. Mandibles rather large, but most parts covered by the labrum; their apical end with a large tooth directed inwards; the basal half their inner edge finely, somewhat irregularly crenulate. Penicillus of mandibles always present, contrary to Lobonyx (see Majer 1987: figs. 242 and 275). Mandibular tendons very large and strongly sclerotised (see Majer 1994: fig. 71).

Antennae always with the first three segments simple, segments 4 to 10 more or less strongly flattened and widened, the last segment distinctly emarginate, approximately "banana-shaped".

Pronotum weakly sclerotised, relatively simple, never strongly convex; without any sharp angles; always approximately as long as wide (length: width ratio ranging from 1: 0.9 to 1: 1.2); with two more or less illdefined oblique impressions in its basal half, one at each side of the disc, sometimes confluent in the middle.

Elytra always more than twice as long as wide together and of more or less subparallel shape (slightly narrowed after the middle in P. viridiflavus ); with short inconspicuous, recumbent ground pubescence intermixed with few longer erect hairs and densely covered with fine punctures, which are often confluent and make up a somewhat rugose texture. Two or three indistinct rows of coarser granules on the elytral disc can be found in some species or some individuals, but they are often completely reduced or invisible within the rugose punctures. Scutellum subtriangular or subrhomboidal, but with all sides more or less rounded and without any clear angles.

Femora and tibiae always simple, without noticeable sexual dimorphism. Middle and hind tarsi (in females also front tarsi) with segments 1–2 subequal; 3–4 also of subequal size, smaller than 1 and 2. Segment 5 longest, almost as long as 3 and 4 together or longer. Claws simple, their base thickened. Male front tarsi thickened, slightly reddish brown, segments 1–3 with a conspicuous, strongly sclerotised black comb along their inner edge. Fourth segment very small and without comb. Male middle and hind tarsi always simple.

Abdomen metallic, weakly sclerotised and without conspicuous characters, except for the last two sternites: In females, they are simple, flat, not emarginate, the last one of somewhat semicircular or slightly parabolic shape. In males, the second last sternite is shallowly emarginate at its apical edge, while the last one is very distinctly emarginate and of species specific shape.

Aedeagus of the same type as in Idgia , compared to Lobonyx with much more robust paramera and phallobase bent downwards (almost straight in Lobonyx ). Endophallic sclerites consisting of a pair of strong sclerites in the basal half and a long row of small denticles leading from these sclerites until the ostium. This is very different from Lobonyx , where the sclerites are restricted to the apical half.

Sexual dimorphism usually affects the size of the eyes, width of the frons, size (and to a smaller extent also shape) of antennae and sometimes (very slightly) shape of the elytra. Females are usually slightly larger in size, although there is a very large overlap. The male protarsal structure with its conspicuous, strongly sclerotised combs is an important character of Prionoceridae ( Champion 1919; Majer 1994). Other special features, like thickened femora, enlarged tibial spurs or strongly curved tibiae which occur in males of some species of Idgia are not known in Prionocerus .