A new genus and sixteen new species of false click beetles (Coleoptera: Eucnemidae) described from the Heredia Province of Costa Rica with several additional records from the Osa Peninsula and Panama Author Otto, Robert L. W 4806 Chrissie Circle, Shawano, WI 54166, U. S. A. Author Muona, Jyrki Finnish Museum of Natural History, Zoology Unit PO Box 17, University of Helsinki, Finland FIN- 00014 Author Córdoba-Alfaro, Jim Insectopia Insect Museum, BioSur Foundation Puerto Jiménez, Península de Osa, Costa Rica jim. cordoba @ biosurcorcovado. org text Insecta Mundi 2023 2023-05-26 2023 991 1 36 journal article 10.5281/zenodo.10831085 1942-1354 10831085 C1D5B819-A964-4679-B090-84CDBBC59D6A Maelodrus costaricensis Otto, Muona and Córdoba-Alfaro , new species Figures 27–29 Diagnosis. This new eucnemid species is distinguished by its elongate bicolored form and vaguely defined lateral antennal grooves from all known eucnemid species present in Costa Rica . Type material. Male holotype : “ COSTA RICA : Heredia ; Est.Bio. La Selva , 50–; 150 m 10°26′N 84°01′W ; Proy. ALAS , INBio-OET” / “ FPM/23 /07; Pentaclethra macroloba; 14 Octubre 1994 ” / “ HOLOTYPE : ; Maelodrus ; costaricensis ♂ ; Otto, Muona & Córdoba-Alfaro; Det. R . L. Otto ; 2019” (red printed label). Holotype to be deposited in INBC . Description. Male holotype : Length, 3.0 mm. Width, 0.75 mm . Body elongate; bicolored with black head, dark brown pronotal disc and elytra, lateral pronotal sides, hypomera and abdomen infuscate reddish; antennae black; legs reddish-brown; head and elytra clothed with short, recumbent yellowish setae, pronotum with elongate, recumbent yellowish setae ( Figures 27–28 ). Head : Surface evenly punctate, somewhat shiny, subspherical; frons convex, without median carina or fovea above frontoclypeal region; apical margin of frontoclypeal region rounded, about 2 times wider than base; interantennal carina absent; mandibles stout, bidentate, densely punctate. Antenna : Filiform to weakly serrate from flagellomeres I–IX, attaining about 3/4 the length of the body; flagellomere I longer than wide, slightly shorter than II; flagellomeres II–VIII each sub-equal, longer than wide; flagellomere IX simple, slightly longer than VIII. Pronotum : Surface somewhat dullish, densely punctate; slightly longer than wide, with moderate, sharp hind angles; lateral sides parallel-sided at basal 2/3, arcuate at apical 1/3; disc convex without fovea or circular fovea; base sinuous. Scutellar shield : Short, sub-triangular, setose, shallowly punctate and distally rounded. Elytra : Distinctly, shallowly striate; interstices slightly elevated; surfaces shiny with dense punctures. Legs : First tarsomere as long as the combined lengths of the remaining four on meso- and metatarsi; tibiae rounded in cross section; metatarsomeres I–III simple; metatarsomere IV very short, excavated, slightly emarginated; metatarsomere V short with simple claws. Venter ( Figure 29 ): Closely punctate, with elongate, recumbent yellowish setae; hypomeron with vaguely defined, lateral antennal grooves; metepisterna parallel-sided; elytral epipleura punctate; metacoxal plates medially 6.0 times wider than laterally. Figures 27–30. Costa Rican macraulacine eucnemids. 27) Maelodrus costaricensis sp. nov. , dorsal habitus. 28) Maelodrus costaricensis sp. nov. , lateral habitus. 29) Maelodrus costaricensis sp. nov. , ventral habitus. 30) Onichodon confluentus sp. nov. , male holotype, dorsal habitus. (Scale: 27–29 = 1.0 mm; 30 = 5.0 mm) Distribution. This eucnemid species is known from a holotype specimen taken from a single location within the province of Heredia . Biology. A single specimen was taken from Pracaxi ( Pentacletha macroloba (Willdenow) Kuntze; Fabaceae ). Larvae and pupae are unknown. Etymology. The specific epithet is derived from a combination of two words, ‘Costa Rica’ and ‘-ensis’, a Latin adjectival suffix meaning “pertaining to”; from which the new species have been taken.