Achalcus bilineatus, Pollet, 2005, 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: 35-37

publication ID 10.1111/j.1096-3642.2004.00141.x


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scientific name

Achalcus bilineatus



Male: Rather small, slender species. Head. Face dark brown, dusted, as wide as ocellus. Frons dark brown. Occiput flat with broad central furrow, dark brown, shining. Uppermost four postocular bristles dark brown, lower seven yellow. Palp ovoid, about 1/3 of eye, brown with basal half yellowish. Antenna with scape and pedicel pale yellow, scape infuscated on less than dorsal half; pedicel narrowly infuscated dorsally; first flagellomere pale brown with less than basoventral 1/3 yellow, rounded triangular, 1.5¥ as long as deep and 1.3¥ as long as scape and pedicel combined. Arista nearly apical, with short pubescence (2nd segment of arista lacking in holotype).

Thorax: Mesonotum, including humeri, reddish yellow and scutellum with large brownish central spot. Uppermost half of pleura contrasting dark brown, lower half reddish yellow. Postnotum concolorous with mesonotum with broad black frontolateral edge and fine central dark line on dorsum. Metapleura with lower 3/5 reddish yellow, uppermost 2/5 dark brown. Seven ac, longer than distance between rows. Sutural bristle absent.

Abdomen with 6th segment small but visible. Abdominal tergites dark brown with 1st tergite largely yellow and 2nd with a few small yellow patches. Sternites yellowish white, darker from 6th onwards; with brown pubescence. Genital capsule brown. Hypopygium with dark aedeagus with subapical dorsal bend; ventral bristle of surstylus simple; VEP and DEP evident; postgonites pale but evident; cercus small, triangular ( Fig. 3A View Figure 3 ).

Wing. Halter slightly infuscated. Wing pale, with R 4+5 and M 1+2 parallel in apical 1/3. Proximal section of vein CuA 1 2.3¥ as long as apical section; CuAx ratio 2.2. Wing length 2.5 mm.

Legs including coxae entirely yellow with only coxa I infuscated along whole length on outer half. Trochanters pale yellow. Femur I with erect ventral bristle inserted at basal 1/5, 1.3¥ as long as femur is deep; with 1–2 strong pv preapical bristles ( Fig. 3B View Figure 3 ). Femur II with one strong ad, one small av and one rather strong pv preapical bristles. Femur III with one strong ad and one strong av preapical bristles. Tibia I with one very weak dorsal bristle at basal 1/4; tibia II with two ad and one pd bristles, basal bristles inserted at basal 1/5 and almost forming ad-pd couple; tibia III with three ad and four (3rd smaller, atypical?) pd bristles and 7–9 small erect ventral setae on basal 2/3. All tarsi yellow. First tarsomere of leg III 0.8¥ as long as 2nd tarsomere. Body length 2.5 mm.

Female. As in male, except for the following: face pale brown. Antenna with 1st flagellomere brownish yellow, rounded triangular, 1.2¥ as long as deep (2nd segment of arista lacking in allotype); six ac. Abdomen with six pubescent segments, dark brown with 1st segment largely whitish yellow on dorsum; 8th segment with eight stout dark brown dornen; cercus reddish yellow. CuAx ratio 1.8. Tibia III with three ad and three pd bristles. Body length 2.7 mm, wing length 2.7 mm.

Etymology. Refers to the dark brown upper pleura that contrasts strongly with the reddish yellow dorsum of the thorax.

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

Allotype. 1♀, same data.  


Mus. Tinro, Vladyvostok


National Biodiversity Institute, Costa Rica