Gastroserica (Gastroserica), 1897

Ahrens, Dirk & Pham, Phu, 2023, Updates on the taxonomy and distribution of Gastroserica Brenske, 1897, Microserica Brenske, 1894, and Moronoserica Ahrens, Lukic & Liu, 2023 (Coleoptera: Scarabaeidae: Sericinae: Sericini), Zootaxa 5346 (5), pp. 551-566 : 557-559

Revised and updated key to Gastroserica (Gastroserica) species (males only):

1 Labroclypeus widest at base, lateral margins narrowed anteriorly. Pronotum without longitudinal median impression. Antennomere 7 in male equal to ¾ of length of club.......................................................... 2

- Labroclypeus widest at middle, lateral margins more or less distinct narrowed towards base, or subparallel. Pronotum with or without longitudinal median impressions................................................................... 6

2 Disc of pronotum with numerous punctures bearing each a robust seta. Metatibia externally finely and sparsely punctate............................................................................ G. (G.) marginalis (Brenske, 1894)

- Pronotum only on sides with coarse punctures bearing each a robust seta. Metatibia externally coarsely and densely punctate. ................................................................................................... 3

3 Right paramere wider and bifurcate at the basis.............................................................. 4

- Right paramere narrow, not bifurcate...................................................................... 5

4 Lateral branch of right paramere short, half as long as the mesal branch. Left paramere more than half as long as right paramere......................................................... G. (G.) vindenensis Fabrizi & Ahrens, 2018

- Lateral branch of right paramere long, as long as the mesal branch. Left paramere less than half as long as right paramere.............................................................................. G. (G.) dembickyi Ahrens, 2000

5 Right paramere moderately narrow (lateral view), ca three times as wide as long; only little longer than the left paramere...................................................................... G. (G.) yingi Ahrens & Pacholátko, 2007

- Right paramere narrow (lateral view), ca six times as wide as long; distinctly longer than the left paramere..................................................................... G. (G.) muongphangensis Ahrens & Pham , new species

6 Disc of pronotum with shallow longitudinal median impression or additionally with a transverse impression behind the middle.............................................................................................. 7

- Disc of pronotum without a shallow longitudinal median impression............................................ 16

7 Disc of pronotum with a transverse impression behind the middle............................................... 8

- Disc of pronotum only with a shallow longitudinal median impression.......................................... 15

8 Eyes strongly protruding, labroclypeus very narrow (ratio maximal width of head including eyes/width of labroclypeus: 1.8– 1.9). Pygidium strongly conical......................................................................... 12

- Eyes weakly protruding, labroclypeus relatively wide (ratio maximal width of head including eyes/width of labroclypeus: 1.48). Pygidium moderately convex. Median transversal impression on pronotum only weak.......................... 9

9 Phallobase with a very short and blunt lateral apical apophysis on right side only. Left paramere trifurcate.............. 11

- Phallobase with a narrow and moderately long lateral apical apophysis on right side............................... 10

10 Left paramere simple; right paramere is a little shorter and more robust (lateral view)............................................................................................ G. (G.) shaanxiana Ahrens & Pacholátko, 2003

- Left paramere bifurcate at base; right paramere little longer and more narrow (lateral view)... G. (G.) hubeiana Ahrens, 2000

11 Median process of the left paramere long; right paramere almost entirely straight........... G. (G.) sichuana Ahrens, 2000

- Median process of the left paramere shorter; right paramere bent ventrally at apex....................................................................................................... G. (G.) fengduana Liu & Ahrens, 2014

12 Median transversal impression on pronotum very distinct and deep, median longitudinal impression more distinct on pronotal disc. Labroclypeus basally strongly narrowed............................... G. (G.) impressicollis (Fairmaire, 1891)

- Median transversal impression on pronotum indistinct and shallow, median longitudinal impression on pronotal disc almost invisible. Labroclypeus basally almost not narrowed........................................................ 13

13 Lateral phallobasal apophysis longer, curved (dorsal view). Left paramere bifurcate; right paramere with a short, sharp, lateral branch............................................................................................. 14

- Lateral phallobasal apophysis shorter, almost straight (dorsal view). Left and right paramere simple.............................................................................. G. (G.) yunnanensis Liu, Ahrens, Bai & Yang, 2011

14 Lateral process of phallobase longer; ventral process of left paramere long, and the lateral short tooth of the right paramere is displaced behind apical half.................................................. G. (G.) mausonensis Ahrens, 2000

- Lateral process of phallobase shorter; ventral process of left paramere short; lateral short tooth of the right paramere is displaced distally to apical half..................................................... G. (G.) carolusi Liu & Ahrens, 2014

15 Punctures on pronotum fine, simple and scarcely scattered; median longitudinal impression fine and superficial. Labroclypeus moderately wide............................................................... G. (G.) herzi (Heyden, 1887)

- Pronotum strongly and densely punctate, between puncture additionally with microscopic fine punctures; median longitudinal impression robust............................................................... G. (G.) sulcata Brenske, 1897

16 Phallobase apically without apophysis. Ocular canthus half as long as ocular diameter.............................. 17

- Phallobase apically always with a more or less long lateral apophysis........................................... 18

17 Aedeagus and parameres wider. Body larger (8.1–9.4 mm).............................. G. (G.) pickai Ahrens, 2000

- Aedeagus and parameres long and narrow. Body smaller (6.8–6.9 mm).............. G. (G.) wenzhui Liu & Ahrens, 2014

18 Phallobase at both sides with apophysis................................................................... 19

- Phallobase only at one side with apophysis................................................................ 22

19 Apex of elytra glabrous, without minute microtrichomes...................................................... 20

- Apex of elytra with a membraneous rim composed of minute microtrichomes. Right apophysis dorsoventrally flattened producing a hook at the tip..................................................... G. (G.) namthana Ahrens, 2000

20 Both apophyses laterally flattened. Apex of elytra glabrous, without minute microtrichomes......................... 21

- Left apophysis dorsoventrally flattened and displaced dorsally over the base of parameres. Color yellow brown, with darks spots on the yellow elytra............................................ G. (G.) stictica Ahrens & Pacholátko, 2003

21 Both apophyses normally sharply pointed. Dorsal surface dark metallic green................ G. (G.) viridis Ahrens, 2000

- Both apophyses rounded at apex. Dorsal surface yellow, with dark brown dots, stripes, or larger maculae (e.g., on pronotum). ......................................................... G. (G.) nigrofasciata Liu, Ahrens, Bai & Yang, 2011

22 Phallobase only on left side with apical apophysis, its surface strongly longitudinally wrinkled....................... 23

- Phallobase only on right side with apical apophysis.......................................................... 25

23 Phallobase ventrally on left side with a carinate lamina. Apophysis of phallobase unevenly narrowed towards apex....... 24

- Phallobase ventrally on left side without any elevations. Apophysis of phallobase evenly narrowed towards sharply pointed apex, and evenly curved ventrally.................................. G. (G.) contaminata Ahrens & Pacholátko, 2003

24 Left apophysis of phallobase sickle-shaped, directed dorsally. Right paramere dorsoventrally widely extended (lateral view) and at apex not hooked....................................................... G. (G.) patkaiensis Ahrens, 2000

- Left apophysis of phallobase almost straight, directed distally. Right paramere dorsoventrally less widely extended (lateral view) and at apex strongly hooked................................... G. (G.) gemellata Ahrens & Pacholátko, 2007

25 Apophysis of phallobase short and wide, apically lobiform and rounded......................................... 28

- Apophysis of phallobase long and sharply pointed........................................................... 30

- Apophysis of phallobase short and sharply pointed.......................................................... 26

26 Left paramere straight, with two long and narrow, distally directed lobes................. G. (G.) kabakovi Ahrens, 2002

- Left paramere simple, not subdivided into two lobes......................................................... 27

27 Left paramere s-shaped (dorsal view), with a basal short, sharp lobe................. G. (G.) haoyui Liu & Ahrens, 2014

- Left paramere weakly reflexed (dorsal view), without basal lobe, straight in lateral view.................................................................................................. G. (G.) jinxiuensis Liu & Ahrens, 2014

- Left paramere straight (dorsal view), without basal lobe, evenly curved dorsally towards apex (lateral view).................................................................................... G. (G.) liboensis Liu & Ahrens, 2014

28 Body length ~ 7.8 mm. Labroclypeus widely rectangular, lateral margins subparallel, only little convergent basally. Parameres well separated from each other.......................................................................... 29

- Body length ~ 5.7 mm. Labroclypeus narrow, lateral margins strongly curved and convergent basally. Parameres fused with each other...................................................................... G. (G.) haucki Ahrens, 2000

29 Left paramere wider (lateral view) and slightly shorter compared to right paramere.......... G. (G.) napolovi Ahrens, 2000

- Left paramere narrower (lateral view) and much shorter compared to right paramere.............................................................................................. G. (G.) cucphuongensis Ahrens & Fabrizi, 2020

30 Lateral margins of labroclypeus strongly reflexed........................................................... 31

- Lateral margins of labroclypeus weakly reflexed............................................................ 33

31 Lateral apophysis in dorsal view distinctly curved and subequal in length to the left paramere........................ 32

- Lateral apophysis in dorsal view almost straight and distinctly shorter than the left paramere........................................................................................... G. (G.) kucerai Ahrens & Pacholátko, 2003

32 Ocular canthus very long and narrow, ratio length of ocular canthus/ocular diameter: 0.53. Smaller species (6.9 mm)................................................................................. G. (G.) angustula Brenske, 1897

- Ocular canthus short, ratio length of ocular canthus/ocular diameter: 0.36. Larger species (8.4–9.7 mm)............................................................................................. G. (G.) roessneri Ahrens, 2000

33 Disc of pronotum with large punctures bearing each a robust seta and being twice as large as smaller ones. Apical apophysis of phallobase apically with a sharp hook. Apex of elytra with a membraneous rim composed of minute microtrichomes....................................................................................... G. (G.) bilyi Ahrens, 2000

- Disc of pronotum only with punctures of equal size which bear only minute setae. Apex of elytra chitinous, without a rim of minute microtrichomes................................................................................ 34

34 Ocular canthus short, ratio length of ocular canthus/ocular diameter: <0.33....................................... 35

- Ocular canthus long, ratio length of ocular canthus/ocular diameter:> 0.42....................................... 38

35 Lateral margins of labroclypeus basally strongly convergent; surface very densely irregularly punctate.............................................................................................. G. (G.) trilineata Ahrens, 2000

- Lateral margins of labroclypeus basally weakly convergent; surface not densely sparsely punctate..................... 36

36 Apophysis of phallobase long, exceeding the parameres in length..................... G. (G.) fanjingensis Ahrens, 2000

- Apophysis of phallobase short, distinctly shorter than the parameres............................................ 37

37 Apophysis of phallobase straight (lateral view). Left paramere half as wide as long......... G. (G.) nikodymi Ahrens, 2000

- Apophysis of phallobase curved strongly dorsally (lateral view). Left paramere one third as wide as long................................................................................. G. (G.) damingshanica Liu & Ahrens, 2014

38 Right paramere composed of two principal lobes. Metatibia externally along the middle not densely and finely punctate. Metatarsomere 1 distinctly longer than the two following tarsomeres combined. Color of pronotum and elytra dark brown (species to separate only by shape of genitalia)............................................................. 39

- Right paramere composed of one lobes only. Metatibia externally along the middle very densely and coarsely punctate. Metatarsomere 1 slightly shorter than the two following tarsomeres combined. Color of pronotum and elytra yellowish brown, sometimes with dark spots (species to separate only by shape of genitalia)........................................ 40

39 Left paramere half as long as right one.......................................... G. (G.) guizhouana Ahrens, 2000

- Left paramere as long as right one.......................................... G. (G.) guangdongensis Ahrens, 2000

40 Lateral apophysis of phallobase laterally flattened and carinate on its dorsal and ventral margin................................................................................................... G. (G.) asulcata Ahrens, 2000

- Lateral apophysis of phallobase circular in cross section and convex at its dorsal and ventral margin................... 41

41 Left paramere distally bifurcate or sinuate at apex (lateral view). Lateral apophysis of phallobase at apex slightly pointed........................................................................... G. (G.) vinhphuensis Ahrens, 2000

- Left paramere distally not bifurcate or sinuate at apex (lateral view); right paramere shorter and more robust. Lateral apophysis of phallobase at apex rounded................................... G. (G.) huaphanensis Ahrens & Pacholátko, 2003