Achalcus brevicornis, Pollet, 2005

Pollet, Marc, 2005, Systematic revision of Neotropical Achalcus and a related new genus (Diptera: Dolichopodidae, Achalcinae) with comments on their phylogeny, ecology and zoogeography, Zoological Journal of the Linnean Society 143 (1), pp. 27-73 : 37-39

ACHALCUS BREVICORNIS SP. NOV. ( FIG. 4 )

Male. Rather small and stout species. Head. Face dark brown, as wide as ocellus. Frons dark brown. Occiput convex ventrally, distinctly concave dorsally, dark brown, slightly dusted. Uppermost postocular bristles black, lower ones brownish. Palp large (3/10 of eye), ovoid, greyish brown. Antenna mainly dark with scape entirely dark and pedicel dark with ventral 2/3 yellow on inner face; first flagellomere dark with basoventral corner yellow, heart- or radish-shaped, 1.4¥ as long as deep and 1.3¥ as long as scape and pedicel combined. Arista 1.7¥ as long as first three joints of antenna, distinctly subapical, pubescent ( Fig. 4B ).

Thorax. Mesonotum mainly brownish black, with humeri, notopleural and postalar areas yellowish and with scutellum brown on disc with broad yellow margin. Pleura (dark) brown, heavily dusted. Postnotum yellowish with black frontolateral triangle. Metapleura dark brown. 5–6 ac, less than 1.5¥ as long distance between rows. Sutural bristle absent.

Abdomen with 6th segment entirely covered by 5th segment. Abdominal tergites including genital capsule entirely blackish brown, shining, with strong marginal bristles. Sternites dark brown, heavily dusted greyish; 5th sternite with strong caudal incision. Genital capsule very small, less than half of height of 5th tergite. Hypopygium. Aedeagus with distinct subapical dorsal bend; ventral bristle of surstylus simple; VEP and DEP evident; postgonites pale but evident; cercus very small, triangular with strong marginal bristles ( Fig. 4C ).

Wing. Halter and wing slightly infuscated, with yellow veins; vein R 4+5 hardly curved, R 4+5 and M 1+2 distinctly diverging. Proximal section of vein CuA 1 1.9¥ as long as apical section; CuAx ratio 1.9. Wing length 2.2–2.4 mm (n = 5) ( Fig. 4A ).

Legs mainly yellow with coxa I reddish brown, infuscated laterally, with pale pubescence; coxa II reddish yellow, and coxa III pale brown. Trochanters reddish yellow. Femora yellow, sometimes slightly infuscated dorsally; femur I without erect ventral bristle and with one strong pv preapical bristle. Femur II with one strong ad and one strong pv preapical bristles. Femur III with one moderately strong ad and one strong av preapical bristles. Tibiae pale yellow; tibia I without dorsal bristles; tibia II with two very strong ad and one very strong pd bristles (1/5 of tibial length), basal bristles forming no ad-pd couple; tibia III with 2–3 strong ad and 2–3 strong pd bristles; with five minute ventral setae. All tarsi with 5th tarsomeres dark; tarsus I yellow, infuscated from apical 1/3 of 1st tarsomere; tarsus II and III dark yellow, gradually infuscated towards apex. First tarsomere of leg III 0.8¥ as long as 2nd tarsomere. Body length 2.3– 2.4 mm (n = 5).

Female. As in male, except for the following: face somewhat wider than ocellus. Antenna with 1st flagellomere rounded triangular with basal half yellow. Femora slightly infuscated dorsally. Abdomen with six pubescent segments; 8th segment pale brown with eight thin dornen; cercus dark brown. Body length 2.7 mm, wing length 2.5–2.7 mm (n = 2).

Etymology. R efers to the modest size of the 1st flagellomere as compared to its Neotropical congeners, except for the representatives of the A. costaricensis species group.

Holotype. 1♂, CHILE: Region de la Araucania, Prov. Malleco, Rio Blanco , 1100–2000 m, ii.1964 (L. Peña) ( CNC; D, hypopygium mounted).

Paratypes. CHILE: 1♂, Region de los Lagos, Prov. Osorno, Lago Puyehue, 80 km E. of Osorno (secondary forest), 17–18.i.1997, YWT ( Bickel ) ( CNC; W, antenna, wing and hypopygium mounted) ; 1♂, same date ( CNC; W); Region del Biobio, Prov. Arauco : 2♂, 2♀, Nahuelbuta, P.N., Road to Caneta (mixed Nothofagus ), 13–14.ii.1997, YWT (Bickel) ( POLLET, CNC; W) ; 1♀, Cord. Nahuelbuta, 41 km E. Cañete, 1070 m, 8.ii.1998 (Woodley) ( USNM; D) .

Figures

Figure 4. Achalcus brevicornis sp. nov. (male). A, wing; B, antenna; C, hypopygium.