Description:
Female: Head horizontal, with a width 1.7 times greater than its length. The vertex behind the ocelli does not have an abrupt bend. The posterior ocelli are very small, not larger than the granular pattern on the vertex, making them difficult to observe even at 56x magnification. The posterior ocelli are located close to the compound eyes; the distance between them is not greater than the diameter of an ocellus. The frons is not concave. The temples are not wide, their width is less than the width of the compound eyes. Compound eyes have a length greater than their width (15:12), longer than the length of the malar space. The head has a small, irregular granular pattern with scattered short hairs. Antennae are 12-segmented, clavate. The scape is 6 times longer than its width, 4 times longer than the radicle and 4 times longer than antennal segment 2. Antennal segment 2 is equal in length to segment 3. Segments 4, 5, and 6 become progressively shorter; segment 6 is small, its width greater than its length. The antennal club has 6 segments, the total length of the club segments is shorter than the length of the scape; the width of each club segment is 7-11 times greater than its length; the last segment of the club has a length and width that are almost equal.
The thorax is longer than it is wide. The mesoscutum lacks a skaphion in the anterior part, the posterior half has 2 short longitudinal grooves, and has a granular pattern similar to that on the head. The scutellum is round at the posterior end, smooth and shiny in the middle, and surrounded by a fine granular pattern. The metanotum is narrow, with a small triangular spine in the middle. The propodeum is short. The two posterior lateral areas have dense hairs. The forewing is 3.3 times longer than wide; the marginal vein is shorter than the stigmal vein, and the postmarginal vein is more than 2 times longer than the stigmal vein.
The abdomen is 1.8 times longer than wide. The first tergite is wider than long, its length shorter than the length of the second tergite. The second tergite is 2 times wider than long. The third tergite is wider than long, its width and length greater than the width and length of the other tergites. Tergites 1 and 2 have longitudinal grooves. The remaining tergites have a small granular pattern.
Body black. Antennae mostly black; radicle black, anterior 1/3 of the scape is slightly brown, posterior part black. Legs dark brown (the middle parts of the femora and tibiae are black, both ends of the tarsi are black).
Male unknown.
Measurements:
Body length 1.1 mm.
Remarks:
This new species is closely related to Opisthacantha keralensis Sharma, 1978, but differs from Sharma’s species in that the third abdominal tergite lacks longitudinal grooves, and the antennae are almost entirely black. The body size is only half the length of Opisthacantha keralensis.
Distribution:
Vietnam: Thai Nguyen.
Type Material:
Holotype, 1 female, Thai Nguyen (Thai Nguyen City), 24/4/1986 (V. Triapitxun).