Glabellula electrica (Hennig)

Evenhuis, Neal L., 2002, Review of the Tertiary microbombyliids Diptera: Mythicomyiidae in Baltic, Bitterfeld, and Dominican amber, Zootaxa 100, pp. 1-15 : 5-6

Glabellula electrica (Hennig)

Proglabellula electrica Hennig, 1966: 16 . Hennig, 1967: 13. Hennig, 1969: 57. Hull, 1973: 59. Schlüter, 1976: 360. Larsson, 1978: 98. Keilbach, 1982: 366. Baroni Urbani & Saunders, 1983: 216. Evenhuis, 1983: 471.

Glabellula electrica (Hennig) . Schumann, 1991: 83. Evenhuis, 1991: 63. Evenhuis, 1994: 339. Evenhuis, 2002b: 29 .

Hennig (1966) described this species based on a single male specimen that unfortunately had some features of the head and one wing cut off during the preparation of the amber piece. He later (1967) gave details of a second specimen from ZMUC that had all the features of the head intact. Hennig’s original (1966) description and supplementary information provided in Hennig (1967) will serve to characterize the species. It is easily distinguished from Glabellula grimaldii , sp.n., the only other Glabellula with a stump vein extending into cell bm+dm by the different shaped first and second antennal flagellomeres (cf. Figs. 2, 3 ).

TYPE. Holotype male from the BALTIC REGION: exact locality unknown, “Th. Hansen, Mon”; deposited in ZMUC. The holotype is mounted in Canada balsam on a slide. Prior to examination by Hennig (1966) the amber piece had been cut and, unfortunately, cuts off a portion of the head and one wing.

OTHER MATERIAL EXAMINED: BALTIC REGION: 1 male, exact locality unknown, BH­139/2; 1 male, exact locality unknown, BH­139/1 (both in HCH); 1 male, exact locality unknown, [no number], C.V. Henningsen ( ZMUC).

REMARKS. Hennig (1966) erected the new genus Proglabellula based on some small difference in wing venation: stump vein on the vein bm­cu + dm­cu extending into cell bm+dm (absent in Glabellula ), vein R4+5 ending in wing margin closer to M1 than vein R1 (this vein ending closer to R 1 in Glabellula ), cell dm + bm longer than in Glabellula . These characters have been shown to be variable in species of Glabellula and do not warrant separate generic status ( Schumann, 1991; Evenhuis, 1991). Additionally, Hennig’s (1967) description of the characters of the antennae of Proglabellula are within the variation exemplified in Glabellula . A further character has been observed by me in the holotype that appears to show a distinct difference: Sclerotization of the first abdominal tergum in Glabellula is characteristically interrupted medially with membrane. In the holotype of G. electrica it appears that there is no interruption of sclerotization. Close examination of the specimen referred to by Hennig (1967) shows that the first abdominal tergum is, in fact, interrupted medially by membrane. This membrane is present, but difficult to distinguish from the sclerotized terga in the holotype.

Glabellula grimaldii Evenhuis , sp.n.

DIAGNOSIS. Most similar to Glabellula electrica in wing venation, both characterized by the presence of a small stump vein on crossvein bm­cu+dm­cu. Glabellula grimaldii can be separated from G. electrica by the different size and shape of the antennal flagellomeres ( Figs. 2, 3 ), the yellowish halter knobs (dark in G. electrica ), and the velvety black abdomen (abdomen with magenta highlights in G. electrica ).

DESCRIPTION. Male and female ( Fig. 6 ). Length: 0.92–1.48 mm (holotype 1.20 mm). Head. Velvety black; eyes dichoptic, separated at vertex by 1.5 x distance between lateral ocelli; front and face black, tip of oral margin paler brown; antennae black; scape minute; pedicel cylindrical, slightly wider than long; first flagellomere ( Fig. 3 ) ovoid, length about 1.5 x greatest width; second flagellomere small, rounded apically, about 1/4 length of first flagellomere; apical sensillum not visible; mentum shiny dark brown; proboscis brown, length approximately 2/3 head height; palpus not evident.

Thorax. Mesonotum and scutellum velvety black, with scattered minute bronzy hairs; pleura brown; coxae and basal 2/3 of femora dark brown; apical 1/3 of femora, and all of tibiae and tarsi yellowish brown; halter stem and knob yellowish.

Wing ( Fig. 6 ). Hyaline; veins brown; costa ends slightly beyond end of R4+5; vein Sc incomplete, ending at level about halfway between origin of Rs and end of vein R2+3; Rs evanescent at connection with R1; vein R2+3 originates slightly beyond middle of Rs; vein R4+5 starting straight to wing margin, slightly sinuous apically, ending in costa beyond level of end of vein M2; vein M1 slightly curved toward wing margin; vein M2 fairly straight to wing margin; small stump vein present on crossvein bm­cu+dm­cu extending into cell bm+dm; vein A1 evanescent.

Abdomen. Dorsum velvety dark brown to black, with scattered minute dark hairs. Sternum with small dark brown sternites surrounded by membrane. Genitalia not dissected.

TYPES. Holotype female from the DOMINICAN REPUBLIC: exact locality unknown, DR­11­18. Deposited in AMNH. Paratypes: DOMINICAN REPUBLIC: 1 male, 1 female in same amber piece, exact locality unknown, DR­14­928 (AMNH); 1 female, exact locality unknown, DR­14­933 (AMNH).

The holotype is in a cut piece of hemispherically shaped amber measuring 12 x 6 mm and is associated with the following inclusions: 6 winged ants, 1 small chironomid, and miscellaneous small debris. The amber is preserved in a cube of clear artificial resin measuring 15 x 9 x 9 mm.

The paratype DR­14­933 is associated with a small phorid fly and some small pieces of debris in the same amber piece. Both paratype amber pieces are preserved in small cubes of clear artificial resin.

REMARKS. See G. brunnifrons , sp.n. above for remarks concerning the association of species of Glabellula with ants.

ETYMOLOGY. The species is named for Dr. David Grimaldi, in honor of his many contributions to the knowledge of amber fossils.

Figures

FIGURES 1 ­ 4. Glabellula antennal flagellomeres. 1. G. brunnifrons, sp. n. 2. G. electrica (Hennig). 3. G. grimaldii, sp. n. 4. G. kuehnei Schlüter.

FIGURES 5 - 8. Habitus. 5. Glabellula brunnifrons, sp. n. (specimen DE- 001) 6. Glabellula grimaldii, sp. n. (specimen DR- 11 - 18). 7. Mythicomyia dominicana, sp. n. (specimen DR- 11 - 9). 8. Mythenteles baltica, sp. n., female habitus (specimen BE- 001).