Cissidium robustum sp. nov. urn:lsid:zoobank.org:act: 8AB09488-EE5E-4F80-AAAE-71E8885D9187 Fig. 41 Etymology Johnson ms name, from the Latin adjective ‘ robustus ’, meaning ‘strong, robust’ and probably referring to appearance of the species. Material examined Holotype SOLOMON ISLANDS • ♂; Guadalcanal, Mt. Austen; 19 Jun. 1963; no. 6487; P. Greenslade leg.; BMNH. Description SIZE. Habitus (Fig. 41A), length 0.63 mm. COLOUR. Dark yellow brown, pubescence, legs and antennae dusky yellow. HEAD. With a shallow median depression between the eyes and a narrow linear ridge posterior to this, width across eyes 0.22 mm; antennomeres III–XI, 0.38 mm; mentum obscured. PRONOTUM. Length 0.18 mm, width 0.28 mm, base with a series of four foveae on each side with slightly wider separation opposite the scutellum, the two inner pairs larger than the outer pair, surface sparsely pubescent without foveolae; sides angulate, convexly narrowed to effaced front angles, concavely narrowed to slightly acute hind angles, sides bordered, the borders not continuing along the posterior margin though there are two short, shallow impressed lines on each side of the median emargination opposite the scutellum (Fig. 41B). ELYTRA. 0.36 mm wide, 0.40 mm long, basal half somewhat closely covered with rather large foveolae contrasting with the pronotum. MESOVENTRITE. Medial extension of collar very widely based, sharply tapering to raised portion of mid-keel; mid-keel wide, sides concave, the hind angles effaced before mesocoxae; keel with ± five setae in basal half tapering to almost parallel-sided, with a rounded termination at base of mesocoxae; mesoventral lateral margins serrate in posterior half (Fig. 41C). METAVENTRITE. Length 0.15 mm, sparsely pubescent, disc simple, distance across spines 0.11 mm. WINGS. Macropterous. GENITALIA. Male aedeagus as Fig. 6 Fa–b, but slightly longer. Females unknown. Remarks Distinguished from other Solomon Islands species in this group by the wider mid-keel.

Published as part of Darby, Michael, 2020, A revision of Cissidium Motschulsky (Coleoptera: Ptiliidae) with seventy seven new species, pp. 1-188 in European Journal of Taxonomy 622 on pages 65-66, DOI: 10.5852/ejt.2020.622, http://zenodo.org/record/3777282