Cissidium

Darby, Michael, 2020, A revision of Cissidium Motschulsky (Coleoptera: Ptiliidae) with seventy seven new species, European Journal of Taxonomy 622, pp. 1-188 : 98-100

Key to Cissidium species in group 4A

1. Species with longitudinal linear depressions on the pronotum ......................................................... 2 – Species without linear depressions on the pronotum......................................................................... 4

2. Linear depressions very faint (best seen with side lighting).................................. C. trangse sp. nov. – Linear depressions well marked ........................................................................................................ 3

3. Linear depressions long almost reaching mid-point of pronotum, pronotum more densely pubescent .......................................................................................................... C. bilineatum sp. nov. – Linear depressions shorter, pronotum more sparsely pubescent ....................... C. arcuatum sp. nov.

4. Mentum triangular ................................................................................... C. triangulum Darby, 2019 – Mentum not triangular ....................................................................................................................... 5

5. Head small, pronotum domed, sides almost parallel before hind angles, base of pronotum wider than elytra ................................................................................................................................................. 6 – Pronotum not so domed, not wider than elytra, head larger in proportion ........................................ 7

6. Pronotal hind angles acute, projected rearwards .............................................. C. seditiosum sp. nov. – Pronotal hind angles rounded, not projected rearward ......................................... C. insulare sp. nov.

7. Pronotum cordate, posterior margin same width as distance across the eyes, elytra almost parallelsided, very small species..................................................................................... C. besucheti sp. nov. – Larger species, pronotal posterior margin clearly wider than distance across eyes .......................... 8

8. Posterior margins of pronotum almost parallel-sided ....................................................................... 9 – Posterior margins of pronotum clearly concave before hind angles................................................ 10

9. Mesoventral lateral margins serrate.......................................................................... C. loebli sp. nov. – Mesoventral lateral margins without serrations.......................................... C. globosum Darby, 2015

10. Mid-keel rounded/tapering posteriorly, without projecting hind angles...........................................11 – Mid-keel with clearly projecting posterior angles........................................................................... 14

11. Mid-keel very narrow parallel-sided then tapering to keel.............................................................. 12 – Mid-keel wider, posterior angles rounded ....................................................................................... 13

12. Mid-keel tapering to keel from end of the very narrow medial process of the collar ......................... ............................................................................................................................ C. visendum sp. nov. – Mid-keel parallel-sided for most of its length before tapering to join keel ......................................... ........................................................................................................................ C. plaumanni sp. nov.

13. Mesoventral collar with two short posteriorly directed processes either side of the medial process .................................................................................................................. C. opacum sp. nov. – Collar without processes either side of the medial process ....................................... C. steeli sp. nov.

14. Mesoventral lateral borders effaced in posterior half ..................................................................... 15. – Mesoventral lateral borders distinct to mesocoxae......................................................................... 16.

15. Pronotum widest in basal half, pubescence sparser.......................................... C. luctuosum sp. nov. – Pronotum widest medially pubescence denser .................................................... C. faustum sp. nov.

16. Sides of mid-keel straight to posterior angles.................................................... C. obscurum sp. nov. – Sides of mid-keel not straight concave or slightly convex .............................................................. 17

17. Sides of mid keel slightly concave same width as the median extension of the collar anteriorly and strongly widening posteriorly ................................................................. C. elongatum Sawada, 2008 – Mid-keel sides concave.................................................................................................................... 18

18. Mid keel sides more pronouncedly concave, narrower at termination of the medial extension of the collar, chaetotaxy of male abdominal ventrites distinctive.................................. C. petri Darby, 2015

– Mid keel sides less pronouncedly concave wider at termination of the medial extension of the collar ................................................................................................................................................ 19

19. Posterior border of pronotum well-marked to emargination opposite the scutellum ...................... 20 – Posterior border of pronotum very short reaching only half way to emargination opposite the scutellum.................................................................................................................. C. eciton sp. nov.

20. Tip of keel sharply pointed .............................................................................................................. 21 – Tip of keel blunt/rounded................................................................................................................. 22

21. Pronotal posterior border very narrow...................................................................... C. sueae sp. nov. – Pronotal posterior border wider, clearly distinct............................................. C. subfaustum sp. nov.

22. Medial extension of collar tapering to a blunt point............................................... C. flavum sp. nov. – Medial extension of collar parallel-sided ........................................................................................ 23

23. Pronotum wider, lateral margins more sharply rounded............................... C. ecuadoriense sp. nov. – Pronotum narrower, sides more smoothly rounded ................................................ C. angusi sp. nov.