Eleusis nigrita, Irmler, 2017

Irmler, Ulrich, 2017, The Neotropical species of the genus Eleusis LAPORTE, 1835 with description of the new genus Eleusima (Coleoptera: Staphylinidae: Osoriinae), Beiträge Zur Entomologie = Contributions to Entomology 67 (2), pp. 275-318 : 287-288

Eleusis nigrita spec. nov.

urn:lsid:zoobank.org:act:BB492AC3-EF93-4F93-90E5-FD266A957102

Figs 9 A-C,29A, 35a

Type material: male Holotype: Panama: Santa Fe, Piedra Alta (- 81.13°W, 8.52°N), dead wood, 26.4.2014, leg. T. Struyve ( UIC) . PARATYPES: Costa Rica: Alajuela, E.B. San Ramón, RB San Ramón , 27 km N & 8 km W San Ramón (84°35.46'W, 10°13.4'N), 810 m elevation, under bark, 2 males, 3 females, 7.7.2000, leg. J. Ashe, R. Brooks, Z. Falin, #CR1ABF00072 ( KNHM) ; Heredia, Selva Biol. Stat., nr. Puerto Viejo de Sarapiqui , male, 18.2.1985, leg. L. Herman, #2118 ( AMNH) ; Panama: Santa Fé, Piedra Alta (- 81.13°W, 8.52°N), dead wood, 7 males, 29 females, 26.4.2014, leg T. Struyve (22 UIC, 13 TSC, 1 BMNH) ; Darién Prov., Mogué (- 78.156°W, 8.24°N), litter layer, male, 10.8.2014, leg. T. Struyve ( UIC) ; Veragua, Cerro Tute , 4 km W of Santa Fé, 850 m elev., male, 30.7.1995, leg. A. Gillogly ( KNHM) ; Bocas de Toro, 7 km N. Boquete, La Culebra Trail (8°48'N, 82°26'W), 1050 m elev., 2 females, 15.8.1995, leg. A. Gillogly ( KNHM) ; Chiriqui, La Fortuna, Cont. Divide Trail (8°46'N, 82°12'W), 1150 m elev. under bark, female, 9.6.1995, leg. J. Ashe, R. Brooks #158 ( KNHM) .

Diagnosis: The species resembles E. nigerrima in size and dark colouration. E. nigrita is still darker than E. nigerrima . Whereas the elytra of E. nigerrima are dark brown to light brown with darker posterior margin, elytra of E. nigrita are totally black. The species are also separated by the shape of the elytra. Whereas the elytra are quadrate in E. nigerrima , they are longer than wide in E. nigrita . The identification should be supported by dissection of the aedeagus. In contrast to E. nigerrima , the central lobe of the aedeagus is without central prominence. Only a slight swelling is visible. In lateral aspect, the apex is slightly curved, whereas it is straight in E. nigerrima and the transparent lobe of the paramere has no fringe of fine setae as in E. nigerrima . According to the sample from Panama with a large number of specimens, no sexual dimorphism such as in E. nigerrima was found. In both males and females, the head length and width was 0.56 ± 0.07 mm, 0.65 ± 0.07 mm (n=6) for males and 0.52 ± 0.06 mm, 0.62 ± 0.06 mm (n=26) for females, respectively (t-test: T=1.5, p=0.14).

Description: Length: 3.2 – 3.5 mm. Colouration: totally black; femoral base black; femoral apex, tibiae and tarsi brown; antennae brown.

Head: on average, 0.53 mm long, 0.62 mm wide; without sexual dimorphism; eyes not prominent; temples as long as eyes; slightly divergent; diagonally narrowed to neck; preocular sides parallel to base of antennae; anterior margin of clypeus sinuate with prominent central part; supraocular groove deep; slightly widened posteriad; irregular punctation moderately deep; sparse; on average, interstices between punctures three to four times as wide as diameter of punctures; setiferous puncture at each end of supraocular groove; several setiferous punctures along anterior margin of clypeus; elongate microsculpture dense; on clypeus weaker than on vertex; on clypeus with transverse striae, on anterior vertex with longitudinal striae; on posterior vertex with diagonal striae; surface slightly shiny.

Antennae nearly as long as head and pronotum combined; first antennomere thicker and longer than following antennomeres; second less than half as long as first; third half as long as first; following antennomeres increasing in width and decreasing in length; fourth antennomere 1.5 times as long as wide; tenth antennomere quadrate; fourth to eleventh antennomere pubescent and with long apical setae.

Pronotum: 0.39 mm long, 0.41 mm wide; widest close to anterior angles; anterior angles smoothly rounded to neck; posterior half continuously narrowed to posterior angles; posterior angles obtuse; posterior margin slightly rounded; punctation as deep as on head, but sparser; on average, interstices between punctures four to five times as wide as diameter of punctures; at anterior margin close to anterior angles, two large and deep punctures with setae; at anterior angles with short lateral impression; within impressions two large setiferous punctures; along lateral margin with few setae; lateral margin interrupted at beginning of posterior half; interruption marked by large setiferous puncture; elongate microsculpture as deep and dense as on head; close to anterior margin with transverse striae; at anterior angles with curled striae; on disc with longitudinal striae; close to posterior margin with diagonal striae; surface slightly shiny.

Elytra: 0.56 mm long, 0.53 mm wide; sides slightly divergent from obtuse humeral angles to posterior angles; posterior angles obtusely angled; punctation as deep and sparse as on pronotum; on central disc with pair of large setiferous punctures; several large setiferous punctures along lateral margin; elongate microsculpture as dense and deep as on head and pronotum; diagonally striate; pointing from humeral angles to suture; surface slightly shiny.

Abdomen with denser and deeper punctation as on elytra; segments with transverse rows of large setiferous punctures; microsculpture with isodiametric reticulation at base of segments; with elongate transverse striae in distal half of segments; basal surface of segments matt, distal surface shinier.

Aedeagus slender; apex slightly curved; along midline of central lobe without prominence; marked by concentration of sensillae; endophallus with two long spurs; one thick long spur and one thinner and shorter spur; paramere slightly shorter than central lobe; widened at apex to transparent lobe; apical margin of transparent lobe with minute sensillae, with only one seta; at base of scape with few sensillae.

Etymology: The species name derived from the Latin word niger meaning black and refers to the totally black colouration of the elytra.

Figures

Fig. 7–12: Eleusis fauveli (7), E. hondurana (8), E. nigrita (9), E. indica (10), E. castanea (11), E. genieri (12); aedeagus in lateral (A)