Glabellula aggregata Evenhuis

Evenhuis, Neal L., 2013, New microbombyliids (Diptera: Mythicomyiidae) from Eocene Baltic and Rovno ambers, with notes on previously described amber species, Zootaxa 3731 (3), pp. 371-380 : 372-374

Glabellula aggregata Evenhuis , new species

( Figs. 1, 2 , 7 , 13 )

Type. Holotype male and two paratypes (one male, one female) (all in the same amber piece; see Fig. 1 ) from Ukraine: exact locality unknown, DU-139. The holotype and paratypes (DU-139b) are embedded in a fairly clear, polished, amber piece, subtrapezoidal in shape, measuring 12 x 10 x 13 x 3 mm by 2–3 mm thick. Rovno amber; Late Eocene. The amber has numerous plant particles. One paratype female is at the edge of the piece and the mesonotum and top of the head were cut during initial preparation of the amber piece. Holotype and paratypes (in same piece) in SIZK.

Diagnosis. Most similar to Glabellula kuehnei Schlüter , but can be distinguished from it by the length of the second antennal flagellomere being 1/3 the length of the first flagellomere (this segment less than 1/5 the length of the first flagellomere in G. kuehnei ), the costa ending near midpoint between the ends of veins R4+5 and M1 (this vein ending just after the end of R4+ 5 in G. kuehnei ); abdominal tergites with yellow laterally (tergites all black laterally in G. kuehnei ).

Description. Male ( Figs. 1, 2 ). Length: 1.2 mm. Head. Occiput, vertex, and mentum black; eyes dichoptic, separated at vertex by 1.5 x distance between lateral ocelli; front and face brown, area surrounding bases of antennae paler brown; antennae dark brown; scape minute; pedicel cylindrical, slightly wider than long; first flagellomere ( Fig. 7 ) subconical-ovoid, length about 1.5 x greatest width; second flagellomere cylindrical, rounded apically, about 1/3 length of first flagellomere; apical sensillum not visible; proboscis brown, length approximately 1/2 head height; palpus not evident.

Thorax. Mesonotum and scutellum dark brown with minute dark hairs; humeral callus, post alar callus, supra alar area and notopleural stripe yellowish white; pleura dark brown except yellow crescent-shaped spot posterodorsally on anepisternum; legs dark brown; hind femur with dense pale hairs distally; halter stem and knob yellowish brown.

Wing ( Fig. 13 ). Hyaline; costa and radial veins brown, other veins yellowish; costa ends beyond end of R4+5 1/ 3 way to M1; vein Sc incomplete, ending about at level of origin of Rs; vein R2+3 originates at basal 1/3 of Rs; vein R4+5 straight to wing margin, ending in costa beyond level of end of vein M2; vein M1 straight toward wing margin; vein M2 slightly curved to wing margin; without stump vein on crossvein bm-cu+dm-cu; anal cell slightly open at wing margin.

Abdomen. Brown, with yellow dorsally on posterior portions of tergites II–VII; with scattered short pale hairs. Genitalia with goxocoxae fused but distinctly bilobed, subconical; gonostylus long, thin, tapering to acute apex; aedeagus bifid, long, thin; other features obscured.

Female. As in male; postabdomen obscured.

Remarks. Having three specimens of Glabellula in the same piece is remarkable since they are relatively rarely found. Because of their known association with ants (Andersson, 1974) and other amber pieces of Glabellula are known with syninclusions of ants (cf. Evenhuis, 2002b), is possible that they became embedded after emerging from an ant nest in or near the plant responsible for the exudate forming the amber; or they were lekking on the tree. The latter behavior has not been observed in any extant species, so this may be a less likely possibility.

Etymology. The specific epithet is from the Latin, aggregatus = “clustered”; referring to the remarkable assemblage of three specimens of this species in the same amber piece.

Figures

FIGURES 1 – 4. Rovno amber Glabellula. Figs. 1 – 2. Glabellula aggregata, n. sp.: 1, amber piece showing positions of holotype male and paratypes. 2, Detail of holotype male. Figs. 3 – 4. Glabellula perkovskyi, n. sp.: 3, amber piece showing position of holotype at upper right; undetermined rhagionid in center of piece. 4, Detail of holotype male.

FIGURES 5 – 12. Antennae and wings of amber fossil Mythicomyiidae. Figs. 5 – 9. Antennae: 5, Glabellula brunnifrons Evenhuis; 6, Glabellula electrica (Hennig); 7, Glabellula perkovskyi, n. sp.; 8, Glabellula kuehnei Schlüter. 9, Riga toni, n. sp. Figs. 10 – 12. Wings: 10, Glabellula perkovskyi, n. sp.; 11, Carmenelectra pernigra, n. sp.; 12, Riga toni, n. sp.

FIGURES 13 – 14. Reconstructions of amber mythicomyiids. 13, Glabellula aggregata, n. sp., drawn from specimen at slightly different angle than shown in Fig. 2; 14, Carmenelectra shehuggme, n. sp., drawn from specimen at slightly different angle than shown in Fig. 17.