Nucleotops Perkins and Balfour­Browne, 1994

Perkins, Philip D., 2004, A revision of the South African endemic humicolous beetle genus Nucleotops Perkins and Balfour­Browne (Coleoptera: Hydraenidae), Zootaxa 559, pp. 1-12 : 3-4

Nucleotops Perkins and Balfour­Browne, 1994

Nucleotops Perkins and Balfour­Browne, 1994: 13 (type species Nucleotops nimbaceps Perkins and Balfour­Browne, 1994 )

Diagnosis. Recognized by the costate elytra (intervals 2, 4 and 6), the admedian longitudinal reliefs of the pronotum, the lateral fringe of setae on the mentum, the eleven articles of the antenna, the lack of hydrofuge pubescence on the venter, the short maxillary palpi and legs, and the gibbose frons.

Description. Body size ca. 1.49 mm to 1.90 mm, form oblong, transversely convex. Antennomeres eleven (6 + 5); third subequal length of first two; pubescent club articles tightly articulated. Eyes small. Frons tumid to gibbose. Margin of head angulate at frontoclypeal suture. Frontoclypeal suture bisinuate. Anterior margin of clypeus straight. Labrum set at angle to clypeus, margin with setal fringe. Maxillary palpus short, shorter than antennae, palpomeres 2, 3 and 4 length ratios ca. 2:1:3, palpomere 3 subglobose, palpomere 4 penicillate. Mentum length slightly less than basal width; lateral border with row of arcuate setae; anterior margin arcuate. Genae rounded, separated by median longitudinal depression; a distinct lateral sulcus for reception of antenna.

Pronotum with well developed lateral depressions, each with anterior and posterior pit; disc with submedian longitudinal costa on each side, smaller elevation lateral to each costa, on posterior 0.5 of disc; anterior margin with hyaline border in middle 0.33; lateral margins converging to base posterior to lateral depression; posterior margin slightly arcuate. Prosternum with procoxae contiguous; prosternum anterior to coxae with one carina on each side and a median carina; antennal cavity very small; a low carina separating pubescent sternal area from non­pubescent inflexed margin of pronotum, latter with two foveae; coxal cavities open behind. Mesosternum at base of intercoxal process with ridge in form of inverted "U"; mesosternum also with short basomedian carina and two low carinae on each side. Metasternum with sparse pubescence, a well developed median fovea near base.

Elytra with ten rows of punctures. Intervals 2, 4 and 6 costate, at least in part. Explanate margin thick, continuing virtually to apices. Abdomen lacking hydrofuge pubescence. First ventrite with apicomedian fovea between metacoxae, on each side an oblique carina from margin of fovea to posterior margin of first ventrite. Intersegmental impressions deep. Intercoxal sternite small, triangular. Legs of moderate build, rather short, each femur slightly excavate to receive tibia; without apparent sexual dimorphism; tarsi 5­5­5; claws simple; metatrochanter small.

Antennal pocket (terminology as in Perkins, 1997) hypomeral, very shallow depression on anterior face of hypomeron, with spiniform setae contiguous with pubescence of prosternum, but not with that of postcoxal projection. The hypomeral carina well­developed; over middle one­third carina contiguous with the notosternal suture, hence hydrofuge pubescence of antennal pocket and that of postcoxal projection are not contiguous; few (two­ten) exocrine pores present along part of carina bordering antennal pocket. Wet­hypomeron wide, varying from smooth to strongly microreticulate, with random exocrine pores varying in density and placement according to species. No organized clusters of pores, or secretion sulcus on hypomeron. Postocular antennal pocket formed by shallowly concave area behind eye, and by contiguous, small concavity on the gena; pocket bordered by distinct postocular carina; setae in postocular part of antennal pocket spiniform. Prosternal antennal cleaner, a cluster of spiniform setae, located on anterior margin of prosternum, adjacent to antennal pocket.