Drusilla nearctica, Eldredge, Taro, 2012

Eldredge, Taro, 2012, Review of the Nearctic species of Drusilla Leach (Coleoptera: Staphylinidae: Aleocharinae), Zootaxa 3300, pp. 45-54 : 48-50

2. Drusilla nearctica , new species

( Figs. 1, 3 , 4–10 , 16–23 )

Type material. Holotype: U.S.A.: 3, “ARKANSAS: Pulaski Co./Pinnacle Ridge Estates/ 2 km W Pinnacle Mtn./ St. Pk., 13 Feb. 1989 /R. Anderson, ex:berl./hardwood litter” ( SEMC). Paratypes (12 ƤƤ, 153): U.S.A.: same data as holotype (12 ƤƤ, 143; SEMC); “ USA AR/Logan Co./Mt. Magazine// 2 June 1986 / Lactarius /R. Leschen// RL213” (3, specimen looks as though extruded genitalia were removed or broken off and were therefore never located; SEMC).

Diagnosis. Drusilla nearctica most closely resembles D. ashei , but can be confidently separated by the following male characters: shape of the median lobe ( Figs. 16–17 ); distal apodeme short, less than four times as long as its width ( Fig. 16 ); aedeagal costal morphology of parameral surface ( Fig. 17 ); paramere with velum obscuring apical lobe in outer lateral view ( Fig. 18 ); chaetotaxy of parameral apical lobe ( Fig. 19 ).

Description. Body ( Fig. 1 ) length on average 3.3 mm (3.1–3.6 mm, n = 10). Hind wings degenerated and absent. Body color with head, pronotum, elytra and most of abdomen dark brown; usually most (if partial, mediobasal portion) of abdominal tergite VI black; frequently tergites V, VII and VIII brown to approaching black and usually not as dark as tergite VI; segments III–IV sometimes with a small basal portion of tergal disk approaching brown compared with rest of given segment; abdominal sternites usually corresponding with tergites in overall color patterning amongst segments; antennae, legs and mouthparts yellowish-brown to brown.

Head subcircular (HW = 0.47 mm, 0.47–0.48 mm; HL = 0.48 mm, 0.47–0.50 mm; HW/HL = 0.98, 0.94–1.00) with faint imbricate microsculpture; eyes small and occupying approximately a third of head length (OL = 0.16, 0.15–0.17 mm; OL/HL = 0.34, 0.30–0.35); setae on vertex directed posteriomedially; labrum ( Fig. 6 ) with distal seta 2 (ds2) posterior of medial setae; epipharynx ( Fig. 7 ) with a generalized athetine form; maxillary ( Fig. 5 ) lacinia with a distal comb consisting of approximately five spines, palpomere IV subulate with filamentous sensillae that are fitted against segment, palpomere IV distally lacking an apical process; labial palpus ( Fig. 4 ) lacking setula β and δ, see generic diagnosis for a further description.

Pronotum slightly transverse (PW = 0.54 mm, 0.51–0.56 mm; PL = 0.48 mm, 0.45–0.51 mm; PW/PL = 1.12, 1.09–1.17) with faint imbricate microsculpture; three pairs of macrosetae present, consisting of one apical pair and two lateral pairs anterior of horizontal midline.

Elytra, together, transverse (EW = 0.59, 0.57–0.63 mm; EL = 0.44, 0.42–0.45 mm; EW/EL = 1.36, 1.27–1.41); each elytron broadly rounded with posterior-most extension medially; elytron with pleural surface forming an approximate right angle with disk; disk with longitudinal basolateral impression; disk of elytron with conspicuously stronger and more irregularly imbricate microsculpture compared with head and pronotum; macroseta on each elytron at subapicolateral margin on dorsal surface.

Abdomen with dorsal surface subglabrous; tergite VIII ( Fig. 20 ) with apical margin sinuate, resulting in a broad medial and acute lateral projections; sternite VIII ( Fig. 21 ) with a blunt medial apex.

Males with vertex of head variably impressed. Pronotum variably, medially impressed. Median lobe ovular in lateral ( Fig. 16 ) and parameral ( Fig. 17 ) view; apical process of median lobe short, extending paramerally; athetine bridge incomplete at aparameral surface, with length of distal apodeme less then four times its width; foramen situated approximately in middle; proximal costa extending most of surface posterior to foramen; median costa extending to apical lobe; arcuate costa sinuate, diverging and closely approximating either side of median costa, again broadly diverging towards apicolateral base of apical lobe. Paramere ( Fig. 18 ), in outer lateral view, with length approximately two times width; velum large and obscuring apical lobe in outer lateral view; apical lobe of paramere ( Fig. 19 ) in inner lateral view with four setulae, subequal in length, crowded at apical margin.

Females with vertex of head with shallow impression that is less pronounced than in males; pronotum usual not medially impressed, but when impressed, to a much lesser degree than in males; spermatheca ( Fig. 23 ) with a simple bend away from side of spermathecal gland, proximal end bulbous in form, distal end slightly dilated with an internal cone.

Etymology. In commemoration, as the first endemic species of Drusilla to the Nearctic.

Figures

FIGURES 1 – 3. Holotypes of Drusilla. Dorsal habitus: 1) D. nearctica; 2) D. ashei. 3) D. nearctica lateral view of head and thorax.

FIGURES 4 – 5. Mouthparts of Drusilla nearctica. 4) prementum, ventral; 5) right maxilla, ventral. Scale bars (0.1 mm): I = 5; II = 4.

FIGURES 6 – 10. Mouthparts of Drusilla nearctica. 6) labrum; 7) epipharynx; 8) left mandible, ventral; 9) right mandible, dorsal; 10) mentum, ventral; 11) left antenna, inner surface with dorsal surface facing down the page. Scale bars (0.1 mm): I = 11; II = 8 – 9; III = 6 – 7, 10.

FIGURES 12 – 19. Male genitalia of Drusilla ashei (12 – 15) and D. nearctica (16 – 19). 12, 16) aedeagus, lateral; 13, 17) aedeagus, parameral; 14, 18) paramere, outer lateral; 15, 19) apex of apical lobe of paramere, inner lateral. Scale bars (0.1 mm): I = 12 – 14, 16 – 18; II = 15, 19.

FIGURES 20 – 25. Details of Drusilla nearctica (20 – 23) and D. ashei (24 – 25). 20) tergite VIII; 21) sternite VIII; 22) female genital segments (tergites IX and X), showing genital plate and spermathecal duct, dorsal; 23) spermatheca; 24) male genital segments (sternite IX and tergites IX and X), dorsal; 25) detail of sternite IX, ventral. Scale bars (0.1 mm): I = 20 – 22, 24 – 25.