Drusilla holoserica, Assing, 2019

Assing, Volker, 2019, Four new species and additional records of Lomechusini from Mindanao, Philippines (Coleoptera, Staphylinidae, Aleocharinae), Linzer biologische Beiträge 51 (2), pp. 789-802 : 792-794

Drusilla holoserica nov.sp. (Figs 6-9, 21-25, 33)

T y p e m a t e r i a l: Holotype ♂: " PHILIPPINES - Mindanao, Araibo, Pantukan, Compostela V., Candalaga Mts., 7°16'35''N, 126°10'13''E, 900 m, 4.V.2019, Shavrin / Holotypus ♂ Drusilla holoserica sp. n. det. V. Assing 2019 " (cAss). Paratypes: 2♂♂: same data as holotype (cAss).

E t y m o l o g y: The specific epithet (Latin, adjective: silky) alludes to silky shine of the abdomen.

D e s c r i p t i o n: Body length 5.3-5.6 mm; length of forebody 2.3-2.4 mm. Habitus slender (Fig. 6). Coloration: head and pronotum blackish; elytra blackish or brown with the postero-lateral portions extensively infuscate; abdomen blackish with the posterior half of tergites III and IV, all of paratergites III, the posterior half of paratergites IV, the posterior portions of tergites, and paratergites V-VII yellowish; legs with the basal halves of the metafemora, the meso- and metatibiae, and the tarsi yellow, and with the profemora, the protibiae, the mesofemora, and the apical halves of the metafemora infuscate; antennae pale reddish-brown; maxillary palpi blackish-brown to blackish.

Head (Fig. 7) nearly 1.2 times as broad as long, posterior angles marked; dorsal surface without distinct impressions or elevation, with dense and distinct punctation, along middle with an impunctate band; interstices with shallow microsculpture. Eyes large and bulging, longer than postocular portion in dorsal view. Antenna (Fig. 8) 2.1-2.2 mm long; antennomeres IV approximately twice as long as broad, V-X of gradually decreasing length, increasing width, and decreasingly oblong, X weakly oblong, and XI elongate, slightly longer than the combined length of IX and X.

Pronotum (Fig. 7) indistinctly oblong and nearly 1.1 times as broad as head, broadest anteriorly; lateral margins weakly sinuate in posterior half in dorsal view; disc with narrow, but distinct median sulcus and with dense and distinct punctation; interstices with distinct microreticulation.

Elytra (Fig. 7) approximately 0.95 times as long as pronotum; punctation dense and somewhat asperate; interstices with distinct microreticulation. Hind wings fully developed.

Abdomen (Fig. 9) with tergites III-V nearly impunctate (except few punctures at posteri- or margins) and with tergites VI-VII very sparsely and finely punctured; all tergites with fine and shallow microsculpture giving the abdomen a silky shine; posterior margin of tergite VII with palisade fringe.

♂: posterior margin of tergite VIII distinctly concave in the middle (Fig. 21); posterior margin of sternite VIII obtusely produced (Fig. 22); median lobe of aedeagus (Figs 23- 24) 0.48-0.50 mm long, with ventral process of rather simple shape; paramere (Fig. 25) 0.45 mm long and with rather large apical lobe.

♀: unknown.

C o m p a r a t i v e n o t e s: Drusilla holoserica is characterized particularly by the slender habitus, the shape of the head (marked posterior angles), distinct microsculpture on the whole body, and by the shape of the aedeagus. It is distinguished from other congeners previously recorded from the Philippines as follows:

from D. bernhaueri (Luzon) by completely different coloration (D. bernhaueri: body yellow with dark head), different head shape (D. bernhaueri: temples acutely produced), and numerous other characters;

from D. butuanensis (Mindanao) by larger size (D. butuanensis: 3 mm), completely different coloration (D. butuanensis: forebody reddish), much denser punctation of the elytra, and other characters;

from D. impressicollis (widespread in the Oriental region) by larger size (D. impressicollis: 3 mm), different coloration (D. impressicollis: pronotum reddish-brown and elytra yellowish to yellowish-brown), a differently shaped head, the presence of microsculpture on the pronotum and elytra (absent in D. impressicollis), and other characters;

from D. laevicauda (widespread in the Oriental region) by larger size (D. laevicauda: 3 mm), the coloration (D. laevicauda: pronotum and elytra brown), coarser and denser punctation of the pronotum and the elytra, matt elytra and pronotum, and other characters;

from D. luzonica (Luzon) by larger size (D. luzonica: 3.5 mm), the coloration of the legs (D. luzonica: legs uniformly yellow), a pronotum without a large impression on either side of the middle, and much denser punctation of the elytra;

from D. philippina (Luzon) by larger size (D. philippina: 3 mm), the coloration of the elytra and the legs (D. philippina: elytra yellowish-brown; protibiae and basal half of mesofemora yellow), and a matt pronotum with dense punctation (D. philippina: pronotum glossy with fine and moderately dense punctation);

from D. plicipennis (Luzon) by larger size (D. plicipennis: 3 mm), completely different coloration (D. plicipennis: forebody reddish), much denser punctation of the elytra, the absence of tubercles on tergites IV-VII, and other characters;

from D. schawalleri (Leyte) by different coloration (D. schawalleri: body reddishbrown), a more slender pronotum (D. kistneri: pronotum broader than long), and by the shapes of the aedeagus and the spermatheca (see KISTNER 1994);

from D. shavrini, D. penicillata , D. spiniventris, and D. breviuter (all Mindanao) by the punctation pattern, the coloration, and the sexual characters. For illustrations of external and the sexual characters, as well as detailed descriptions of these species see ASSING (2019).

D i s t r i b u t i o n: The type locality ( Fig. 33 ) is situated in the very east of Mindanao. The specimens were sifted from wet litter near a river in a secondary forest at an altitude of 900 m.

Figures

Fig. 33: Locality Compostela Valley (photo: A. Shavrin).