Genus Ischnopoderona (Scheerpeltz, 1974), stat. n.

(Figs. 3–17)

Tachyusa (Ischnopoderona) Scheerpeltz, 1974: 229 .

Type species: Tachyusa (Ischnopoderona) gracilicornis Scheerpeltz, 1974: 229 (by monotypy).

Diagnosis. Ischnopoderona can be recognized by the combination of the following characters: body slender, parallel­sided; ligula narrow (Fig. 5), bifid to the base or nearly so, lobes parallel­sided; maxillary palpi elongate and weakly widened apically (Fig. 4); antennae long, extending from 1/2 to 3/4 of elytral length and very slightly increasing in width apically; head without infraorbital ridge; pronotal hypomera fully visible in lateral view; elytral lateral sides arcuate, widest in the middle (Fig. 9); abdomen distinctly constricted at base, widest at level of tergites V and VI, tergites III–V distinctly transversely impressed at base, at least first impression coarsely punctate, tergite V distinctly longer than VII; sternites strongly transversely impressed at base; tarsal formula 4­5­5.

Redescription. Body. Small to medium sized, length 2.0– 3.4 mm. Body slender, parallel­sided, convex, glossy (Fig. 3).

Head. Circular, temples parallel­sided or arcuately narrowed to hind angles; eyes protruding from lateral contours of head; head without infraorbital ridge. Antennae long to very long, very slightly increasing in width apically, extending from 1/2 to 3/4 of elytral length.

Mouthparts. Maxillary palpi 4­segmented (Fig. 4), palpomere 1 very short, palpomere 2 elongate, slightly widened apically, palpomere 3 distinctly longer than 2, weakly widened towards apex, palpomere 4 short, subuliform. Galea long and slender, slightly shorter than lacinia (Fig. 4). Labial palpi 3­segmented (Fig. 5), palpomere 1 elongate, longer than palpomeres 2 and 3 together, palpomere 2 shorter and narrower than 1, palpomere 3 narrower and much longer than 2. Ligula (Fig. 5) narrow, bifid to the base or nearly so, lobes parallel­sided. Mandibles curved towards apex, right mandible (Fig. 6) with very small, indistinct molar tooth at middle of inner margin, faintly serrate in dorsal molar region. Labrum (Fig. 7) transverse, moderately deeply arcuately emarginate apically and with characteristic arrangement of setae. Mentum (Fig. 8) trapezoidal, with 4 long setae on each side, apical margin straight, anterior angles rounded.

Thorax. Pronotum quadrate to longer than wide, moderately to distinctly convex, glossy, widest in apical third, lateral sides sinuately narrowed to hind angles. Pubescence at midline of three types: directed entirely anteriorly, directed posteriorly in apical 1/4 and anteriorly in basal ¾ or directed posteriorly in apical half and anteriorly in basal half; pubescence at postero-lateral parts directed obliquely laterally or straight anteriorly (Fig. 10). Hypomera fully visible in lateral view. Mesocoxae varies from narrowly to widely separated (Figs. 12–17). Mesosternal process varies from narrowly triangular, rounded at apex, extending to 1/2 of mesocoxae and nearly reaching apex of metasternal process (Fig. 12–13) throughout intermediate states (Figs. 14–16) to wide, broadly rounded at apex, extending to about 1/3 of mesocoxae and separated from long, rectangular metasternal process by short, transverse isthmus (Fig. 17). Mesocoxal cavities not or margined posteriorly by fine bead.

Elytra. Quadrate, lateral sides distinctly arcuate, widest in the middle, postero­lateral angles distinctly emarginate (Fig. 9).

Legs. Elongate, metatarsus long, ranging from 3/4 to 4/5 the length of metatibia; basal segment of metatarsus longer than following two tarsal segments combined; tarsal formula 4­5­5.

Abdomen. Distinctly constricted at base, widened posteriorly, widest at level of tergites V and VI, tergites III–V distinctly transversely impressed at base, at least first impressions coarsely and densely punctate, tergite V distinctly longer than VII, sternites III–V moderately to strongly transversely impressed at base, impressions coarsely and densely punctate.

Median lobe of aedeagus short to relatively long and slender, straight or more­or­less bent ventrally in lateral view; gradually narrowed to apex or subparallel­sided and abruptly narrowed apically in ventral view; apex of median lobe rounded, hooked or constricted apically (lateral view); ventral process large and prominent, differs in size and shape between species; internal sac with a few pairs of sclerites differing in size and shape. A combination of these characters is most useful for differentiating species of Ischnopoderona .

Remarks. The examination of the type species of Ischnopoderona as well as other species classified within this genus, clearly show that they form a well­defined monophyletic group characterised by several synapomorphies (see phylogenetic part). Therefore, Ischnopoderona is here regarded as a distinct genus.

The genus Ischnopoderona is closely related to the genera Tachyusa Erichson, 1837, Ischnopoda Stephens, 1835 and Gnypeta Thomson, 1858 . It can be easily distinguished from these genera by the following key:

1. Abdomen distinctly constricted at base; tergite V moderately transverse, 1.2–1.8 times wider than long; elytral postero­lateral angles distinctly emarginated; elytral lateral sides strongly arcuate and widest in the middle; sternites III–V strongly transversely impressed at base...................................... 2

– Abdomen weakly constricted at base; tergite V strongly transverse, at least 2.0 times wider than long; elytral postero­lateral angles slightly emarginated; elytral lateral sides slightly arcuate and widest in posterior half; sternites III–V slightly transversely impressed at base .................................................. 3

2(1). Ligula bifid in apical half, lobes divergent apically; maxillary palpus 3 clearly widened apically; apical margin of mentum distinctly concave; mandible with large molar tooth on right mandible; antennae clearly increasing in width towards apex; abdomen more or less parallel sided; abdominal transverse impressions with longitudinal ridges between punctures ......................... Tachyusa Erichson

– Ligula divided to base, or nearly so, lobes parallel­sided; maxillary palpus 3 weakly widened apically; apical margin of mentum not concave, straight; mandible with small, indistinct molar tooth on right mandible; antennae weakly increasing in width towards apex; abdomen distinctly widened posteriorly; abdominal transverse impressions without longitudinal ridges between punctures ....................... ...................................................................................................................... Ischnopoderona (Scheerp.)

3(1). Ligula bifid in apical half, lobes divergent apically; galea length slightly shorter than lacinia; basal segment of metatarsus longer than the following two tarsal segments combined. Ischnopoda Stephens

– Ligula divided to base, or near base, lobes parallel­sided; galea subequal in length to lacinia; basal segment of metatarsus shorter than the following two tarsal segments combined ..... Gnypeta Thomson