Isarthrus striatus Otto, Muona and Córdoba-Alfaro, 2023

Otto, Robert L., Muona, Jyrki & Córdoba-Alfaro, Jim, 2023, 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, Insecta Mundi 2023 (991), pp. 1-36 : 18-20

Isarthrus striatus Otto, Muona and Córdoba-Alfaro , new species

Figures 35–36

Diagnosis. The new eucnemid species can be readily distinguished from any macraulacine members of Eucnemidae present in Costa Rica by the presence of an interantennal carina, a wide lateral antennal groove which is widest in the middle, simple tarsal claws and dark colored dorsum with reddish-brown antennae and legs. The new species differs from the Nearctic Isarthrus calceatus LeConte by its antennal grooves widest in the middle, striate elytra and shorter flagellomeres II–III. Isarthrus calceatus have parallel-sided antennal grooves, poorly developed striae on the elytra, and slightly longer flagellomeres II–III.

Type material. Female holotype: “ COSTA RICA: Prov. Heredia; Est.Bio. La Selva , 50–; 150 m 10°26′N 84°01′W; 24 Feb 2004; INBio-OET-ALAS transect” (“24 Feb” handwritten on label) / “ 24 Febrero 2004; Malaise; M/26/768” / “ HOLOTYPE:; Isarthrus ; striatus ♀; Otto, Muona & Córdoba-Alfaro; Det. R. L. Otto; 2019” (red printed label). Holotype to be deposited in INBC.

Paratypes. 4 ♀♀: COSTA RICA: 1 ♀, “COSTA RICA: Heredia; Pr: La Selva Bio. Sta.; 3 km s. Pto. Viejo ; 10°26′N 84°01′W ” / “ ii–iv.1993, P. Hanson, Malaise Trap ” / “ PARATYPE:; Isarthrus ; striatus ♀; Otto, Muona & Córdoba-Alfaro; Det. R. L. Otto; 2019” (yellow printed label) ( INBC) ; 1 ♀, “COSTA RICA: Heredia; Pr: La Selva Bio. Sta.; 3 km s. Pto. Viejo ; 10°26′N 84°01′W ” / “ iv–v.1993, P. Hanson, Malaise Trap ” / “ PARATYPE:; Isarthrus ; striatus ♀; Otto, Muona & Córdoba-Alfaro; Det. R. L. Otto; 2019” (yellow printed label) ( INBC) ; 1 ♀, “COSTA RICA: Heredia; Est.Bio. La Selva, 50–; 150 m 10°26′N 84°01′W; Proy. ALAS, INBio-OET” / “M/04/111; 01 Junio 1993; Bosque primario” / “ PARATYPE:; Isarthrus ; striatus ♀; Otto, Muona & Córdoba-Alfaro; Det. R. L. Otto; 2019” (yellow printed label) ( INBC) ; 1 ♀, “COSTA RICA: Heredia; Est.Bio. La Selva , 50–; 150 m 10°26′N 84°01′W; Proy. ALAS, INBio-OET” / “M/10/172; 03 Augosto 1993; Bosque primario” / “Collection of the Global; Eucnemid Research Project; (Robert L. Otto)” (green framed white label) / “ PARATYPE:; Isarthrus ; striatus ♀; Otto , Muona & Córdoba-Alfaro ; Det. R. L. Otto ; 2019” (yellow printed label) ( GERP). Paratypes are to be deposited in INBC and GERP.

Description. Female holotype: Length, 8.5 mm. Width, 2.5 mm. Body elongate; dark brownish-black; antennae and legs dark reddish-brown; head, pronotum and elytra clothed with short, recumbent yellowish setae ( Figure 35 ). Head: Surface somewhat shiny, subspherical with crowded punctures; frons convex with slight circular impression above interantennal carina, poorly developed median carina present; interantennal carina present; apical margin of frontoclypeal region weakly trilobed, more than 2 times wider than base; mandibles stout, bidentate, densely punctate. Antenna: Filiform from flagellomeres I–IX, attaining about 1/3 the length of the body; flagellomere I longer than wide, longer than II; flagellomeres II–III each slightly longer than wide, sub-equal, each shorter than I and IV; flagellomeres IV–V each longer than wide, sub-equal, longer than III, shorter than VI; flagellomeres VI–VIII each longer than wide, sub-equal; flagellomere IX slightly longer than VIII. Pronotum: Surface somewhat shiny, with deep, crowded punctures; quadrate, with well-developed, sharp hind angles; sides parallel-sided at basal 1/2, arcuate at apical 1/2; disc convex, slightly depressed near base above scutellar shield; base sinuous. Scutellar shield: Quadrate, sub-triangular, shallowly punctate, setose and distally rounded. Elytra: Very shallow striae present; interstices slightly elevated; surfaces shiny, closely punctate. 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 excavated; metatarsomere V elongate with simple claws. Venter ( Figure 36 ): Closely punctate, with short, recumbent silver-colored setae; hypomeron with basally opened, lateral antennal grooves, widest in the middle; metepisterna parallel-sided; elytral epipleura punctate; metacoxal plates medially 3.0–6.0 times wider than laterally.

Variations. Four female paratypes were examined. These paratypes measured 7.0– 8.5 mm long and 2.0– 2.5 mm wide. One female paratype is as large as and just as wide as the holotype. The remaining three paratypes are shorter and narrower than the holotype. Median carina on the frons are evident in two paratypes and absent in the other two paratypes.

Distribution. This eucnemid species is known from five specimens taken from La Selva within the province of Heredia.

Biology. Two paratypes were taken from a primary forest. Three specimens were taken from a Malaise trap. Larvae and pupae are unknown.

Etymology. The specific epithet is derived from the presence of well-developed striae on the elytra which serves as one of the best feature to distinguish the new species from the Nearctic I. calceatus .

Figures

Figures 35–39.Costa Rican macraulacine eucnemids. 35) Isarthrus striatus sp. nov., dorsal habitus. 36) Isarthrus striatus sp. nov., ventral habitus. 37) Absensiugum brunneum sp. nov., male holotype, dorsal habitus. 38) Absensiugum brunneum sp. nov., male holotype, ventral habitus. 39) Absensiugum brunneum sp. nov., Male aedeagus, dorsal view. (Scale: 35–36 = 5.0 mm; 37–39 = 1.0 mm)