Adiscus Gistel, 1857

Duan, Wen-Yuan & Zhou, Hong-Zhang, 2022, Revision of the genus Adiscus Gistel, 1857 (Coleoptera: Chrysomelidae, Cryptocephalinae) from mainland China, Zootaxa 5096 (1), pp. 1-80 : 5-7

Genus Adiscus Gistel, 1857

Adiscus Gistel, 1857a: 604 ; Gistel 1857b: 92; Monrós & Bechyně, 1956: 1123; Gressitt,1942: 330; Gressitt & Kimoto, 1961: 114; Kimoto & Gressitt, 1981: 323; Medvedev, 2008: 194; Schöller et al., 2010: 607; Bezděk 2020: 176.

Type species: Phaedon nigromaculatum Kollar & Redtenbacher, 1844 .

= Dioryctus Suffrian, 1860: 3 ; Weise, 1903: 33; Jacoby, 1908: 176; Gressitt, 1942: 330; Chûjô, 1954: 143; Monrós & Bechyné, 1956: 1123 (as synonym of Adiscus ). Type species: Dioryctus porculus Suffrian, 1860 .

= Atropidius Chapuis, 1874: 175 ; Weise, 1903: 33 (as synonym of Dioryctus ); Kimoto, 1964: 141 (Arthopidius, error). Type species: Atropidius improbus Chapuis, 1874 .

= Falsodioryctus Pic, 1955: 21 ; Gressitt & Kimoto, 1961: 114 (as synonym of Adiscus ); Kimoto, 1964: 141 (Ealdodioryctus; error). Type species: Falsodioryctus sinensis Pic, 1955 (synonym of Dioryctus nigripennis Jacoby, 1890 ).

Diagnosis. Body short and ovate, strongly convex. Face flat, in frontal view, eyes reniform and emarginated, antennae usually reaching elytral humeri. Pronotum pentagonal and convex, posterior margin entirely abutting elytra; much broader posteriorly than anteriorly, posterior width about twice as long as pronotal length; anterior margin nearly straight; posterior margin sinuate with fine serration, and medially produced as a sharp angle ( Fig. 1A ). Scutellum invisible from above. Elytra as broad as pronotum at base, humeri somewhat prominent; disc punctures weak and arranged in 11 regular striae; lateral margins distinctly expanded ventrally and forming a round or angular lobe at basal 1/4–1/3 of elytra; the lobe angle measured as shown in Fig. 1B . Prosternum broad, usually trapezoidal, lateral margins raised, forming ridge-like structures with variation between species. Pygidium with dense punctures and short pubescence. Female with a large round deep fovea in the middle of ventrite V, fringed with pubescence on lateral margins.

Adiscus can be separated by the following characters from other genera outside the Chinese fauna: by the strong lobe on the lateral margin of elytron and special morphological variation of prosternum. In China, Adiscus can also be distinguished from Coenobius Suffrian, 1857 by concealed scutellum and the widely sperated eyes; and from Melixanthus Suffrian, 1854 by the convex body and the concealed scutellum.

Key to species of Adiscus from mainland China

1. Elytron entirely reddish or pale, except for basal margin black.................................................. 2

- Elytron partly or entirely black.......................................................................... 13

2. Shorter than 3 mm in length............................................................................. 3

- Longer than 3 mm .................................................................................... 8

3. Pronotum entirely black................................................................................ 4

- Pronotum reddish with basal margin blackish; length 1.8–2.3 mm ............................................... 5

4. Elytron reddish; pronotum feebly rounded and distinctly converging from base to apex; length 2.3–2.5 mm ................................................................................................. A. nigricollis (Gressitt)

- Elytron yellowish; pronotum feebly rounded and only slightly converging from base to apex; length 2.0–3.0 mm.............................................................................................. A. klapperichi (Pic)

5. Prosternum with lateral ridges strongly elevated, and hind angle of prosternum black................................ 6

- Prosternum with lateral ridges weakly elevated, and hind angle of prosternum yellowish brown, pronotum sparsely punctate; length 2.8 mm ...................................................................... A. inornatus Chen & Pu

6. Elytron pitchy black, with two yellowish marks; lateral ridges of prosternum strongly elevated; length 2.3 mm ...................................................................................... A. tanae Duan & Zhou , sp. nov.

- Elytron entirely pale, ochraceous or reddish brown, without marking............................................ 7

7. Elytron reddish; antennomeres 1-4 brownish-yellow, 5-11 dark brown; length 1.9–2.1 mm ............... A. exilis (Weise)

- Elytron yellowish; antennomeres all yellowish, length 2.5–2.9 mm ............... A. ningshanensis Duan & Zhou , sp. nov.

8. Male abdominal ventrite I between metacoxae with brush of erect hairs; mandibles reddish brown with black apex; prosternum with elevated longitudinal-median ridge; length 4.2–5.0 mm................................ A. pubiventris Medvedev

- Without the above character combination.................................................................. 9

9. Venter entirely pale................................................................................... 10

- Thoracic sterna black; length 3.0–4.0 mm..................................................... A. pectoralis (Pic)

10. Elytral stria 7 (below the humerus) grooved anteriorly; epipleural lobe almost angulate near middle................... 11

- Elytral stria 7 not grooved anteriorly; epipleural lobe strongly sinuate; length 3.7–4.5 mm ............... A. mouhoti (Baly)

11. Pronotum distinctly punctate; elytron pale testaceous in basal 1/2; length 4.1 mm .......... A. chekianga Gressitt & Kimoto

- Pronotum impunctate; elytron unicolored................................................................. 12

12. Elytron reddish, and epipleural lobe distinct, forming an angle of 110°; length 3.3 mm ............. A. fracticeps (Gressitt)

- Elytron yellowish and epipleural lobe not so distinct, forming an angle of 130°; length 3.2–3.5 mm ........................................................................................... A. daofuensis Duan & Zhou , sp. nov.

13. Pronotum distinctly punctate........................................................................... 14

- Pronotum impunctate or indistinctly punctate.............................................................. 23

14. Pronotum very densely and strongly punctate, red fulvous; elytra, venter and apical antennal segments infuscate; length 2.3–2.5 mm ............................................................................ A. punctithorax Medvedev

- Without the above character combination................................................................. 15

15. Epipleural lobe slightly feeble; pronotum with 2 balck spots nearly anterior margin, elytron with 2 black band; length 3.9 mm ............................................................................. A. bimaculicollis Chen & Pu

- Epipleural lobe large and arcuate, without the above character combination...................................... 16

16. Dorsum entirely black................................................................................ 17

- Dorsum yellowish or reddish brown, elytron with black marking or not......................................... 18

17. Prosternal central ridge sharp and acute; elytral row intervals without minute punctures; epipleural lobe large and arcuate; length 3.8–4.5 mm .................................................................... A. weigeli Medvedev

- Prosternal central ridge absent; elytral row intervals scattered with minute punctures, epipleural lobe slightly feeble; length 2.6–2.9 mm ............................................................................... A. niger (Chen)

18. Spermatheca S-shaped................................................................................ 19

- Spermatheca falcate.................................................................................. 21

19. Elytral striae distinctly and strongly punctate; elytron with 4 black spots, rectangular arrangement; length 3.7–4.0 mm......................................................................................... A. maculatus (Weise)

- Elytral striae finely punctate, indistinct; elytron without 4 regular black spots..................................... 20

20. Superior eye-lobes separated by greater distance than antennal insertions; elytron reddish brown, with black markings, variegated; only distributed in Tibet; length 3.0– 3.6 mm .......................................... A. speciosus Tan

- Superior eye-lobes separated by same distance with antennal insertions; elytron ochraceous, with 7 black bands; distributed in Fujian and Yunnan; length 2.1–2.6 mm .................................................... A. tibialis Chen & Pu

21. Aedeagus without pubescence on lateral sides; elytron black, with a median transverse ovate reddish brown spot; length 2.6–3.1 mm ................................................................................... A. annulatus (Pic)

- Aedeagus with pubescence on lateral sides; elytron without above character...................................... 22

22. Elytron entirely black, humeri strongly prominent; length 4.3–5.0 mm......................... A. nigripennis (Jacoby)

- Elytron yellowish brown, humerus with a black stripe, weakly prominent; length 2.5–3.2 mm ........... A. humeralis (Pic)

23. Epipleural lobe of elytron large and arcuate, distinct......................................................... 24

- Epipleural lobe of elytron absent, feeble or not developed.................................................... 30

24. Dorsum entirely metallic blue, venter black and above surface of femora, apex of femora and tarsi reddish brown; length 3.2–3.6 mm ............................................................................ A. crassicornis Tan

- Dorsum not metallic blue.............................................................................. 25

25. Elytron of male black, with a round medium-sized yellowish-brown spot, elytron of female reddish brown; length 3.7–5.1 mm ................................................................................. A. bicoloriceps (Pic)

- Elytron without above characteristics.................................................................... 26

26. Venter largely black; lateral ridge of prosternum strongly elevated.............................................. 27

- Venter yellowish brown, with the same color as dorsum...................................................... 29

27. Pronotal lateral margins with narrow black stripe; elytron reddish brown, with a ring of dark purple band along margins, except median suture; length 3.6–4.0 mm........................................................... A. lushuiensis Tan

- Pronotum entirely reddish or yellowish brown, except the black margin......................................... 28

28. Head black behind antennal insertions; elytron with 4 black spots, sometimes apical part of suture black; length 2.9–3.5 mm .................................................................................. A. yunnanus Medvedev

- Elytron yellowish brown, basal region with transversely broad black stripe, with a big round black spot behind the elytral middle region, or elytron entirely black, epipleuron yellowish brown; length 2.3–3.0 mm....... A. kweiyangensis (Gressitt)

29. Lateral ridge of prosternum broad and high, elevated; length 2.3–2.7 mm ....................... A. bodhisatva (Gressitt)

- Lateral ridge of prosternum broad but low, not strongly elevated; length 2.4–2.7 mm .................... A. glabrous Tan

30. Dorsum unicolorous, entirely black or metallic blue......................................................... 31

- Dorsum not unicolorous, pronotum and elytron with different color or elytron with black markings................... 32

31. Dorsum black; male maxillary and labial palpi strongly thickened; epipleural lobe slightly feeble; length 2.0– 2.3 mm ........................................................................................... A. grandipalpus Tan

- Pronotum black, elytron metallic blue; male maxillary and labial palpi normal; epipleural lobe absent; length 2.0– 2.3 mm ........................................................................................... A. cyaneus Tan

32. Apex of maxillary palp swollen, securiform; elytron with a broadly transverse black stripe along the basal margin.............................................................................................. A. transversalis Tan

- Apex of maxillary palp normal; elytral without above characteristic............................................ 33

33. Venter yellowish brown, elytron with 4 black spots, the base two joined together; length 2.2–2.6 mm A. occipitalis Chen & Pu

- Venter largely black, elytron entirely black................................................................ 34

34. Elytral striae coarsely punctate and distinct, interstriae with scattered minute punctures; length 2.3–2.8 mm ............................................................................................... A. atripennis Chen & Pu

- Elytral striae finely punctate, indistinct, interstriae without scattered minute punctures; length 2.6–3.0 mm.................................................................................................. A. variabilis (Jacoby)

Figures

FIGURE 1. Displaying the angle measurement of the genus Adiscus on pronotum and elytra: A. angle of pronotum basal margin; B. angle of elytra epipleural lobe.