Cryptopleurum pygmaeum d’Orchymont, 1913

Jia, Fenglong & Zhang, Ruijuan, 2017, A review of the genus Cryptopleurum from China (Coleoptera: Hydrophilidae), Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) 57 (2), pp. 577-592 : 589-591

Cryptopleurum pygmaeum d’Orchymont, 1913

( Figs 39‒46 )

Cryptopleurum pygmaeum d’Orchymont, 1913: 15 . Cryptopleurum pygmaeum: HANSEN (1999: 309) : catalogue.

Type locality. Formosa [= Taiwan], Taihorin.

Type material examined. PARATYPE: 1 spec. ( ISNB): ‘ Taihorin / Formosa / H. Sauter, 23.90ºN 121.08ºE, VII, 1911 // Coll. A. d’Orchymont // Cryptopleurum / pygmaeum / Co-type d’Orch // Para- / type .’; 1 spec. ( ISNB): ‘ Taihorin / Formosa / H. Sauter, 23.90ºN 121.08ºE, VII.1991 // Coll.A. d’Orchymont // Para- / type’ .

Additional material examined. None.

Redescription. Length 1.5 mm. Yellow brown with head black. Elytra with intervals elevated apically and laterally ( Fig. 41 ), intervals much broader than striae, with vague irregular punctures on intervals, seventh and eighth striae very close and in a same groove, interval eight much lower and narrower than others ( Fig. 42 ). Metaventrite with a curved fine elevated line enclosed mesocoxal cavity that derived from femoral line near anterolateral angle of metaventrite ( Fig. 45 ), middle portion of elevation smooth between coarse punctures but slightly shagreened around edges. Aedeagus ( Figs 43, 44 ): length of parameres and phallobase combined ca. 4.3× as long as basal width of both parameres. Paramere ca. 1.1× as long as phallobase, apex broadened with membrane projecting slightly inwards subapically. Median lobe ca. 6.2× as long as width at midlength, gradually narrowed apically.

Differential diagnosis. This species can be easily distinguished from the other known species except C. ferrugineum by its smaller size and the metaventrite with a curved elevated line enclosing the mesocoxal cavity, being sharply defined mesally, and laterally connected to the femoral lines near anterolateral angle. It can be separated from C. ferrugineum by its smaller size, elytra with the seventh and eighth striae being very close in the same groove, and interval eight being distinctly narrower than the neighboring intervals.

Biology. Unknown.

Distribution. So far only known from China (Taiwan) and Vietnam.

A key to the Chinese species of Cryptopleurum (modified from d’ORCHYMONT 1926)

1 Elytra with the seventh and eighth striae completely separate, interval eight as wide as neighboring intervals ( Figs 34, 35 ). Metaventrite with a curved elevated line enclosing mesocoxal cavity, sharply defined mesally and laterally connected to femoral lines near anterolateral angle ( Fig. 36 ). Apical sixth of median lobe strongly narrowed ( Figs 37, 38 ). ......................................................................... C. ferrugineum Motschulsky, 1863

‒ Elytra with the seventh and eighth striae very close in the same groove, interval eight distinctly narrower than neighboring intervals ( Figs 5 , 12 , 20 , 29 , 42 ). Metaventrite with or without fine elevated line enclosing mesocoxal cavity. ........................................... 2

2 Size 1.3–1.5 mm. Metaventrite with a curved fine elevated line totally enclosing mesocoxal cavity and laterally connected to the femoral line ( Fig. 45 ). ................................. ................................................................................... C. pygmaeum d’Orchymont, 1913

‒ Size 1.6–2.2 mm. Metaventrite with anterolateral portion bearing different microsculpture, not delimited by a line at all, or at most slightly delimited by a short elevated line laterally ( Figs 6 , 15 , 22 , 30 ). ......................................................................................... 3

3 Pronotum with double punctation, shagreened between punctures ( Figs 23 , 31 ). Elytral striae strongly impressed from base to apex, elytral intervals 2‒5 and 7‒9 highly convex or costiform, punctures on intervals fine, at most as coarse as the smaller ones on pronotum. ................................................................................................................................ 4

‒ Pronotum with punctures of the same size only ( Figs 4 , 16 , 46 ), interstices smooth or with short longitudinal microsculpture. Elytral striae weakly impressed in basal half, somewhat impressed apically, intervals simple or moderately convex apically ( Figs 1, 3 , 9, 11 ), punctures on intervals almost as coarse as those on pronotum. ......................... 5

4 Each elytral interval with dense irregular punctures at least on basal half ( Fig. 20 ), punctural striae distinctly narrower than interval ( Fig. 20 ). Elytral intervals highly convex but not costate. Aedeagus slender, length of parameres and phallobase combined ca. 5.5× as long as basal width of both parameres combined. Median lobe ca. 10.0× as long as width at middle, distinctly narrowed in ca. apical third. Parameres ca. 1.4× as long as phallobase ( Fig. 21 ). .................................................... C. coomani d’Orchymont, 1926

‒ Each elytral interval only with a row of fine setiferous punctures, punctural striae distinctly wider than intervals on basal half ( Figs 26, 29 ) and as wide as or slightly wider than interval on posterior fourth ( Fig. 26 ). Elytral intervals sharply costate. Aedeagus stout, length of parameres and phallobase combined ca. 4× as long as basal width of both parameres. Median lobe ca. 5.3× as long as width of middle, distinctly narrowed about apical eighth. Parameres ca. 2.3× as long as phallobase ( Figs 27, 28 ). ................. ....................................................................................... C. sulcatum Motschulsky, 1863

5 Elytra yellowish brown ( Fig. 9 ), dark individual more or less brown except apex ( Fig. 11 ). Pronotum, elytra and metaventrite with finer and moderate dense punctures ( Figs 12, 15, 16 ). Head, pronotum and metaventrite with distinct short longitudinal microsculpture between punctures ( Fig. 16 ). Parameres distinctly expanded outwards subapically, median lobe broad, almost parallel at basal fourth to fifth, abruptly narrowed at apical fifth and gradually narrowed apicad ( Figs 13, 14 ). ........... C. subtile Sharp, 1884

‒ Elytra black or blackish brown. Pronotum, elytra and metaventrite with coarser and dense punctures ( Figs 4, 5, 6 ). Head and metaventrite without fine longitudinal microsculpture ( Fig. 6 ), pronotum only with very fine scale-like microsculpture extremely laterally ( Fig. 4 ). Parameres not expanded outwards subapically, median lobe broad, basal two-thirds almost parallel, and then gradually narrowed apically ( Figs 7, 8 ). ....... .......................................................................................... C. minutum ( Fabricius, 1775)

Figures

Figs 39–46. Cryptopleurum pygmaeum d’Orchymont, 1913. 39–41 – habitus (39 – dorsal; 40 – ventral; 41 – lateral view). 42 – lateral part of right elytron (A – seventh stria, B – eighth stria). 43–44 – aedeagus (43 – dorsal, 44 – ventral view). 45 – meso- and metaventrite. 46 – pronotal punctation.

Figs 32–38. Cryptopleurum ferrugineum Motschulsky, 1863. 32–34 – habitus (32 – dorsal; 33 – ventral; 34 – lateral view). 35 – lateral part of right elytron (A – seventh stria; B – eighth stria). 36 – meso- and metaventrite. 37–38 – aedeagus (37 – dorsal, 38 – ventral view).

Figs 1–8. Cryptopleurum minutum Fabricius, 1775. 1–3 – habitus (1 – dorsal; 2 – ventral; 3 – lateral view). 4 – pronotal punctation. 5 – dorsolateral part of right elytron (A – seventh stria; B – eighth stria). 6 – mesoventral plate and metaventrite; 7–8 – aedeagus (7 – dorsal; 8 – ventral view).

Figs 9–16. Cryptopleurum subtile Sharp, 1844. 9–11 – habitus (9 – dorsal; 10 – ventral; 11 – lateral view). 12 – dorsolateral part of left elytron (A – eighth stria; B – seventh stria). 13–14 – aedeagus (13 – dorsal; 14 – ventral view). 15 – metaventrite. 16 – pronotal punctation.

Figs 17–23. Cryptopleurum coomani d’Orchymont, 1926. 17–19 – habitus (17 – dorsal; 18 – ventral; 19 – lateral view). 20 – dorsolateral part of right elytron (A – seventh stria; B – eighth stria). 21 – aedeagus (dorsal, lateral and ventral view). 22 – meso- and metaventrite. 23 – pronotal punctation.

Figs 24–31. Cryptopleurum sulcatum Motschulsky, 1863. 24–26 – habitus (24 – dorsal; 25 – ventral; 26 – lateral view). 27–28 – aedeagus (27 – ventral, 28 – dorsal view). 29 – dorsolateral part of right elytron (A – seventh stria, B – eighth stria). 30 – meso- and metaventrite. 31 – pronotal punctation.