The acutiuscula species-group

Diagnosis. Forewing length 5.0–8.0 mm, with the ratio of length to maximum width 2.6–3.5. Moths of the acutiuscula species - group share a dark forewing usually with two small yellow costal spots (inner and outer costal spots); in the male genitalia, the uncus is slenderly elongate in most species, the gnathos is absent, or weakly sclerotized laterobasally and membranous or invisible anteriorly, the transtilla is narrowly extended or dilated, and the sacculus is not separated or only distally free from the valva; in the female genitalia, the ductus bursae is sclerotized entirely or partly, and the corpus bursae has 0−2 signa.

The acutiuscula species-group includes eight known species: M. fustiformis (Wang, 2006) (Wang 2006a), M. magnidentata Wang, 2020 (In Zhu et al. 2020), M. mirabilis (Wang, 2003), M. olivaria (Wang, 2006) (Wang 2006a), M. peditata (Wang, 2006) (Wang 2006a), M. projecta Yin, 2019 (In Yin & Cai 2019), as well as M. acutiuscula (Wang, 2004) and M. flavimaculata (Christoph, 1882) from among the unassigned species (Wang et al. 2020). Two new species are described below.

Key to species of the acutiuscula species-group base on male genitalia

1 Uncus bilobed distally (Wang 2003: Fig. 19)....................................................... M. mirabilis

- Uncus not bilobed..................................................................................... 2

2 Valva with two apical spines (Fig. 17).................................................... M. rectivalva sp. nov.

- Valva without an apical spine............................................................................ 3

3 Ventral margin of valva with several denticles along basal 2/3 (Zhu et al. 2020: Fig. 23)................ M. magnidentata

- Ventral margin of valva without a denticle................................................................. 4

4 Ventral margin of valva with a large heavily sclerotized sub-quadrate plate (Fig. 16)............... M. aculeolata sp. nov.

- Ventral margin of valva without a plate.................................................................... 5

5 Ventral margin of valva with a furcate process at base (Wang 2006a: Fig. 2)............................ M. fustiformis

- Ventral margin of valva without a furcate process at base...................................................... 6

6 Valva convex before middle............................................................................. 7

- Valva convex medially or beyond middle.................................................................. 9

7 Sacculus sub-rectangular (Yin & Cai 2019: Fig. 6)................................................... M. projecta

- Sacculus sub-triangular or equilaterally triangular............................................................ 8 8 Sacculus sub-triangular, aedeagus shorter than valva (Lvovsky 2015: Fig. 19)........................ M. flavimaculata

- Sacculus equilaterally triangular, aedeagus longer than valva (Wang 2006a: Fig. 1)........................ M. peditata

9 Valva convex medially, aedeagus without cornutus (Wang 2004: Fig. 8)............................... M. acutiuscula

- Valva convex beyond middle, aedeagus with cornuti (Wang 2006a: Fig. 16).............................. M. olivaria