Male. Labeled: “Sri Lanka: Sinharaja Forest Reserve, 6.3645N, 80.4786E, 22–24-viii-2016, D. Rubinoff, M. San Jose and U.G.A.I. Sirisena, FF638, zingerone trap, molecular voucher ms7321.” Deposited in the University of Hawaii Insect Museum (UHIM).

Dacus ancoralis is similar to other Asian species of Dacus with a red-brown scutum lacking the yellow medial and lateral vittae and with a costal band of uniform width that crosses vein R₄₊₅ over the entire length of the wing, but does not reach vein M, and fuscous cells bc and c, such as Dacus polistiformis (Senior-White), D. wallacei White, D. longicornis Wiedemann, D. insulosus Drew and Hancock and D. discretus Drew and Romig. Dacus ancoralis differs from D. polistiformis and D. wallacei in lacking spines on the femur of the front legs, and it differs from all other aforementioned species by having dark fulvous postpronotal lobes. The closely related D. vijaysegarani (Figure 2A–E) Drew and Hancock is easily separated by its black scutum, mostly black abdomen and black legs.

Figure 1. 

Dacus (Mellesis) ancoralis sp. n. A head B head and scutum C abdomen D wing E lateral view F Abdominal tergum II, with anchor-shaped marking.

Figure 2. 

Dacus (Mellesis) vijaysegerani (Drew and Hancock). A head B head and scutum C abdomen D wing E lateral view.

Figure 3 shows the maximum likelihood tree based on combined COI-5P and COI-3P regions (1535 base-pairs [bp]) for Dacus ancoralis and the closest congeners in our dataset. In the COI-3P fragment (836 bp), the minimum p-distance to Dacus vijaysegarani is 1.38%, and in the COI-5p DNA barcode fragment (658 bp) it is 2.43%. Because there is only one specimen of D. ancoralis we cannot test for reciprocal monophyly. The overall next closest relative in our dataset is D. siamensis, at a minimum p-distance of 8.61% in COI-3P, 8.81% in COI-5P.

Figure 3. 

Maximum likelihood tree based on COI (1535 base-pairs) sequence data. Bootstrap support is indicated on the respective branches. Scale bar indicates substitutions per site.

Head (Figure 1A). Vertical length 2.00 mm. Frons, of even width, length 1.06 times as long as broad; red-brown with fuscous around orbital setae and on anteromedial hump; latter covered by short red-brown hairs; orbital setae dark fuscous: one pair of superior and two pairs of inferior fronto-orbital setae present; lunule fulvous. Ocellar triangle dark fuscous. Vertex fuscous. Face fulvous with medium sized oval black spots in each antennal furrow, a fuscous band along lower margin between spots and a dark fuscous triangular marking below antennal sockets; length 0.55 mm. Genae red-brown, with fuscous subocular spot; dark fuscous seta present. Occiput fulvous and yellow along eye margins; occipital row with two parallel rows of adjacent setae (with 11 and 17 setae). Antennae with segments 1 (scape) and 2 (pedicel) fulvous and segment 3 (first flagellomere) fuscous; a strong red-brown dorsal seta on segment 2; arista black (fulvous basally); length of segments: 0.83 mm; 0.70 mm; 1.23 mm.

Thorax (Figure 1B, E). Scutum red-brown with a broad light fuscous lanceolate pattern on its posterior third, anteriorly prolonged into three very narrow lines reaching anterior margin, light fuscous narrow outer bands parallel to lanceolate pattern and reaching notopleural suture. Pleural areas red-brown except a broad vertical dark fuscous band in front of mesopleural stripe, a large dark fuscous spot occupying central portion of katepisternum, and a dark fuscous spot on katepimeron above hind coxa. Yellow markings as follows: notopleura (notopleural callus); narrow parallel-sided mesopleural (anepisternal) stripe, reaching midway between anterior margin of notopleura and anterior notopleural seta dorsally, continuing to katepisternum as a transverse spot and to scutum as moderately broad yellow markings along anterior margin of notopleural suture; lower 25% of anatergite (remainder dark fulvous); anterior 70 % of katatergite (remainder black). Postpronotal lobes dark fulvous. Medial and lateral postsutural vittae absent. Postnotum red-brown with two broad longitudinal fuscous bands. Scutellum yellow except for narrow black basal band. Setae (number of pairs): 1 scutellar; prescutellar absent; 1 intraalar; 1 posterior supraalar; 1 anterior supraalar; 1 mesopleural; 2 notopleural; 4 scapular; all setae well developed and black.

Legs (Figure 1E). Femora and tibiae orange-brown, except for fuscous ventral surface of hind femur; mid-tibiae each with an apical black spur; tarsi fulvous.

Wings (Figure 1D). Length 7.00 mm; basal costal (bc) and costal (c) cells fuscous and covered with microtrichia; remainder of wings colorless except dark fuscous subcostal cell, broad dark fuscous costal band overlapping R₄₊₅ and of uniform width, not reaching vein M; anal streak absent; supernumerary lobe weakly developed.

Abdomen (Figure 1C, E, F). Elongate, clavate and petiolate; terga tightly joined but with medial protuberances; pecten of cilia present on tergum III; posterior lobe of surstylus short; abdominal sternum V with a slight concavity on posterior margin. Tergum I and sterna I and II longer than wide. Tergum I orange-brown with apical third yellow and a median light fuscous band on apical half of red-brown portion. Tergum II orange-brown with medial dark fuscous narrow band and two short basal bands, lateral to medial band, forming an anchor-shaped pattern, and broad fuscous markings on lateral margins. Tergum III orange-brown with dark fuscous as along base and extended to whole lateral margins and into a triangular medial band. Tergum IV orange-brown with dark fuscous medial basal triangular marking, narrowly along base of tergum and broadly along entire lateral margins. Tergum V orange-brown with dark fuscous medial basal triangular marking, and large lateral bands covering basal half of tergum and reaching lateral margins. A pair of basally fuscous and apically orange-brown ceromata (shining spots) on tergum V. Abdominal sterna dark except pale sternite II.

The name ancoralis is a noun in apposition that refers to the anchor-shaped fuscous pattern on abdominal tergum II in the holotype (Figure 1F).

Although Dacus ancoralis is genetically closely related to D. vijaysegarani and there is only one specimen, they do not appear to be sympatric, with D. vijaysegarani only known from Malaysia, Thailand and Vietnam, and with the clear differences in coloration of all body parts we are confident in describing it as a new species. The holotype of Dacus ancoralis was referred to as “ms7321 Dacus (Mellesis) sp-78”, sister to D. vijaysegarani, in the seven-gene phylogeny presented in San Jose et al. (2018). It keys to couplet 37 (p 467) in the Keys to the Fruit Flies of South-East Asia (Drew and Romig 2016), where it can be added as a unique combination of having dark fuscous postpronotal lobes and a red-brown scutum. Dacus ancoralis was collected in a trap with zingerone lure. A number of other species of Dacus were found to be drawn to zingerone in recent years (Doorenweerd et al. 2018), but because there is only one specimen known we cannot yet confirm it as a zingerone-attracted species. This species is assigned to subgenus Mellesis, as defined by Drew and Romig (2013) based on the petiolate abdomen with tergum I longer than wide and sternum V weakly concave apically, the presence of anterior supraalar setae and absence of prescutellar setae, the combined length of antennal segment greater than vertical length of face, and the absence of anal streak on wing. Its nearest relatives all belong to subgenus Mellesis (Figure 3).