Achalcus tibialis, 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 : 47

ACHALCUS TIBIALIS SP. NOV. ( FIGS 10 , 11 )

Male. Rather large, slender and elegant species. All bristles and pubescence on body (including postoculars an prothoracic bristle) yellowish white, bristles and pubescence of legs reddish yellow. Head. Face whitish yellow, very narrow (0.5¥ as wide as ocellus) but eyes not touching. Frons dark brown. Occiput strongly convex, dark brown, shining. Palp very large (almost 3/5 of eye), elongate ovoid, pale reddish yellow. Proboscis pale, large, as long as eye. Antenna entirely pale yellow with extreme apex and arista dark; first flagellomere elongate triangular, 1.9¥ as long as deep and 1.1¥ as long as scape and pedicel combined. Arista as long as first three joints of antenna, inserted apically on outer face, entirely dark, with short pubescence ( Fig. 10B ).

Thorax entirely yellowish white with thin dark line on anterior part between ac, extending till 2nd dc. Postnotum with very small blackish frontolateral triangle. six ac, 2¥ as long as distance between rows. Sutural bristle absent.

Abdomen with 1st abdominal tergite yellowish white, 2nd dark brown with large white lateral spots, 3rd till 5th black; 2nd sternite white, sternites brownish black from 3rd onwards; 5th sternite with caudal invagination. Genital capsule blackish brown. Hypopygium. Aedeagus dark, with slight subapical dorsal bend; ventral bristle of surstylus with small apical flag; VEP and DEP evident; postgonites pale, distinctly bifurcate; cercus very long and tapering, with midventral enlargement, baring long curved bristles ( Fig. 11 ).

Wing. Halter pale, squamal fringe yellowish white. Wing pale, with yellow veins, with R 4+5 and M 1+2 slightly diverging apically. Proximal section of vein CuA 1 2.4¥ as long as apical section; CuAx ratio 1.3. Wing length 3.2 mm ( Fig. 10A ).

Legs yellowish white including coxae and tarsi. Femur I with erect ventral bristle at basal 1/6, 1.6¥ as long as femur is deep, with one row of rather strong (0.5 ¥ femur depth) inclined av bristles (also basad of basoventral bristle) and four erect very strong pv preapical bristles ( Fig. 10C ). Femur II with one row of enlarged inclined av bristles, and one row of erect strong pv bristles; three pv bristles in basal 1/4 as long as femur is deep, more apical bristles inclined until middle of femur; seven pv bristles in apical half 1.5¥ as long as femur is deep; femur II with one strong ad, two strong av and one strong pv preapical bristles ( Fig. 10D ). Femur III with one strong ad and one very strong av preapical bristles. Tibia I with one moderately strong dorsal bristle at basal 1/4; tibia II with two strong (> 3 ¥ tibial depth) ad and one strong pd bristles, basal bristles forming ad-pd couple at about basal 1/4; with ten very strong (3 ¥ tibial depth) erect ventral bristles, apical bristles clustered ( Fig. 10D ). Tibia III with three very strong ad and three very strong pd bristles; with long pd pubescence in basal half and 4–5 minute ventral setae amid dense pubescence. Tarsus I pale yellow, slightly darker than tibia; tarsus III with large incision at comb. First tarsomere of leg III 0.7¥ as long as 2nd tarsomere. Body length 2.7 mm.

Female. U nknown.

Etymology. Refers to the peculiar ventral chaetotaxy of tibia II in this species.

Holotype. 1♂, COSTA RICA: Cartago, 4 km NE Canon, Genesis II, 2350 m, 9∞42–43¢N, 83∞54–55¢W, 2350 m, viii.1995, MT (Hanson) ( INBio; W, hypopygium, antenna, wing and leg II mounted).

Figures

Figure 10. Achalcus tibialis sp. nov. (male). A, wing; B, antenna; C, coxa and femur I; D, femur and tibia II.

Figure 11. Achalcus tibialis sp. nov. (male). Hypopygium with cercus separated.