1	Tip of scutellum polished, not interrupting posterior, polished band of scutellum at middle; vein r-m of fore wing arising from vein r+3-SR so that areolet is 4-sided	2
–	Rugose tip of scutellum interrupting posterior, polished band of scutellum at middle; areolet of fore wing various in shape	5
2	Metacarp short, shorter than twice as long as its distance from apex of marginal cell; T2 highly polished, shorter than T3	Diolcogaster brevivena Zeng & Chen, sp. n.
–	Metacarp longer, at least twice as long as its distance from apex of marginal cell; T2 more or less rugose to rugulose, slightly longer than T3	3
3	Propodeum with a weak and incomplete median keel	Diolcogaster alvearia (Fabricius, 1798)
–	Propodeum with a strong and complete median keel	4
4	Vein r of fore wing as long as or slightly shorter than vein 2-SR; disc of scutellum finely, discretely punctate; T2 with a shiny and feebly longitudinally striated raised median field, irregularly shaped but distinctly narrowed behind; the lateral fields striate-rugose, but reduced toward lateral margin	Diolcogaster praritas Zeng & Chen, sp. n.
–	Vein r of fore wing much longer than vein 2-SR; disc of scutellum with dense punctures, larger laterally; T2 transverse, shortened medially, with a raised pentagonal median field, shiny but densely rugulose all over	Diolcogaster punctatiscutum Zeng & Chen, sp. n.
5	Antennae of female very short, segments 10–12 being hardly longer than wide; metacarp short, shorter than 1.5× as long as its distance from apex of marginal cell; T2 divide by two curved, more or less rugose and ][-shaped grooves into three fields of which the middle one is triangular and narrowest behind	Diolcogaster spreta Marshall,1885
–	Antennae of female long, all segments distinctly longer than wide; metacarp longer, at least twice as long as its distance from apex of marginal cell; T2 never that sculptured	6
6	Vein r-m of fore wing arising from vein r+3-SR so that the areolet is 4-sided; vein 1-CU1 much shorter than 2-CU1	7
–	Vein r-m of fore wing more or less interstitial with vein r (1st abscissa of the radius) so that the areolet is virtually 3-sided; relative length of vein 1-CU1 variable	8
7	T2 as long as T3; T3 with traces of rugosity; vein r arising from distal 1/2 of pterostigma, far behind the middle	Diolcogaster laetimedia Zeng & Chen, sp. n.
–	T2 distinctly shorter than T3; T3 highly polished; vein r arising from distal 1/2 of pterostigma, but only slightly behind the middle	Diolcogaster perniciosa (Wilkinson, 1929)
8	T3 as heavily sclerotised as T2, the two tergites together forming a sculptured carapace, beneath which the more apical tergites are completely or partially hidden; fore wing marked with brown patches at apex	9
–	T3 usually smooth, polished and never forming a carapace with T2 such as above; fore wing without patches at apex	10
9	Ovipositor sheath with a thickened seta; T1 distinctly widened posteriorly; posterior margin of T3 rounded, emarginated medially; forewing with apical spot dark brown	Diolcogaster chaoi (Luo & You, 2003)
–	Ovipositor sheath without trace of apical, modified setae; T1 slightly widened posteriorly; T3 subrectangular, with posterior margin straight, not emarginated medially; forewing with apical spot slightly infuscate	Diolcogaster bifurcifossa Zeng & Chen, sp. n.
10	T2 without trace of median field, rugose more or less all over; vein 1-CU1 distinctly shorter than 2-CU2; mesoscutum shiny, with very dense and evenly discrete punctures	Diolcogaster ineminens Zeng & Chen, sp. n.
–	T2 with a more or less distinct median field that varies in shape but is never triangular or widened posteriorly, though sometimes is widened anteriorly; vein 1-CU1 slightly longer than 2-CU2; sculptures of mesoscutum variable	11
11	T1 linear, very long and narrow, more than thrice as long as its width; propodeum with weak median keel; T2 with a distinctly raised pentagonal median field that is sharply-sided and with smooth and shiny surface, area beside median field setose and also smooth and shiny; pterostigma brown, except basal pale spot	Diolcogaster grammata Zeng & Chen, sp. n.
–	T1 not linear, not more than 2.5× as long as its width; propodeum with strong complete median keel; T2 without such a raised pentagonal median field; pterostigma without a basal pale spot	12
12	T2 with an elongated median field that is not triangularly widened behind; vein 1-R1 more than four times as long as its distance from the apex of the marginal cell; POL much longer than OD; vertex and frons densely rugose; face at upper half with very indistinct median longitudinal carina	Diolcogaster translucida Zeng & Chen, sp. n.
–	T2 with an ill-defined median field, only slightly swollen; vein 1-R1 with distal end almost reaching to apex of marginal cell; POL about 1.5× as long as OD. Vertex finely transversely striate; frons polished and without setae in large part but densely rugulose and setose adjacent to eye margin; face without any trace of median keel	Diolcogaster pluriminitida Zeng & Chen, sp. n.