Body shape fusiform, broad and strongly flattened; head transverse, with a suture between antennal insertions; sensillae on apical margin of epipharynx arranged in a pattern of anterior or a-sensilla, and lateral or ε-sensilla; prementun with medial pseudopore field present, with at least a few pseudopores in an irregular rectangular array, but pseudopores are extended to the lateral pseudopore field; mandibles with a large velvety patch completely occupying the base, composed of nine to eleven transverse rows of large teeth that are reduced in size to the base; labium with short rounded ligula, entire, and not divided; pronotum transverse, approximately 1.5 times wider than long, wider on medial third; mesocoxal cavities not separated by meso- and metaventrite processes; mesoventrite process short with apex acuminate; metaventral process medium-sized, marginate and with apex subobtuse; isthmus not present; tergite VII with lateral margin modified to form a structure-like wall on each side, which apparently provides support between tergite and sternite (only visible because of transparency on slides), and with an apical sclerotized plate attached internally (only visible because of transparency on slides) to receive tergite VIII; tergite VIII modified to form a horn (Figs 1–2), in females and males; spermatheca with small and approximately spherical capsule, median and posterior portion of spermathecal stem (duct) sinuate; process of crista apicalis long, almost straight and parallel to median lobe, rounded at the apex.

Figure 1. 

Habitus of Placukorna ipsa Santiago-Jiménez, gen. n. and sp. n. (Holotype).

Figure 2. 

Lateral view of Placukorna ipsa Santiago-Jiménez, gen. n. and sp. n. (Holotype).

Body length 2.5–3.0 mm. Body shape fusiform, broad and strongly flattened; pronotum transverse. Tergite VIII modified to form a horn (Figs 1–2) in both, males and females.

Head. Transverse, with a suture between antennal insertions; surface with coarse punctures densely distributed. Antennomeres 4–10 transverse (Fig. 3). Eyes prominent, occupying almost two thirds of head length. Neck absent (Fig. 4). Infraorbital carina present. Coeloconic sensilla absent (Fig. 3).

Figures 3–14. 

Placukorna ipsa Santiago-Jiménez, gen. n. and sp. n. male (8, 12, 14) and female (9, 13). 3 antenna 4 head 5 epipharynx 6 ligula, prementum, and labial palpi 7 pronotum 8 sternite VIII 9 sternite VIII 10 sternite VII tergite VIII 12 median lobe, lateral view 13 spermatheca 14 paramere, lateral view. Scale bars: 3–4, 7–11 = 0.2 mm; 5–6, 12–14, = 0.1 mm.

Mouthparts. Labrum: with 7 setae on each side of the midline; most of the setae on anterior half; with 17–19 sensory pores on each side of midline; sensillae on apical margin of epipharynx, arranged in a pattern of anterior or a-sensilla, and lateral or ε-sensilla (Fig. 5), one on each side of the midline (see Ashe 1984, Santiago-Jiménez 2010); apico-medial margin of epipharynx not modified to setose or with spinose process; basal region of epipharynx with six pores, more or less in one transverse row; medial region of epipharynx with 35–40 pores in an irregular array (Fig. 5); medial region of epipharynx without a multiporose sensory structure on each side of midline; basal region epipharynx without pores on each side to form a transverse row. Mandibles: asymmetrical; right mandible with a medial tooth, poorly defined; with serration on apical half of mandibles; with a large velvety patch completely occupying the base, composed of nine to eleven transverse rows of large teeth that are reduced in size to the base; prosthecal setae are not bifurcated on medial area. Maxilla: with a row of nine spines (in one specimen only seven were counted) and scarce setae contiguous on apical half of lacinia, basal half almost glabrous, with only five setae; with scarce setae on apical third of galea and two spines, medial and basal third almost glabrous; with pseudopores on the cardo. Labium: with short rounded ligula, entire, and not divided. Prementum with two medial setae insertions widely separated; medial pseudopore field present, with at least a few pseudopores in an irregular rectangular array, but pseudopores are extended to the lateral pseudopore field (Fig. 6); lateral pseudopore field composed of one setose pore, and two asetose pores (Fig. 6); with setae on adoral margin of hypoglossa, but without setae on aboral margin. Mentum without reticulate microsculpture on surface; with scarcely distributed pores on mentum, around fourteen on each side of midline; with a pair of macrosetae on each apico-lateral margin, one macroseta is longer than the other is; surface with eight setae on each side of midline. Labial palpi with only two segments.

Thorax. Pronotum transverse (Fig. 7), approximately 1.5 times wider than long, wider on medial third; surface finely punctured, moderately dense to dense; without reticulate microsculpture; setae dense on surface; apparently without macrosetae on surface. Scutellum with surface smooth, with some punctures, and moderately covered with short setae. Elytra together slightly wider on apical area, but on basal area slightly wider than pronotum; surface punctured moderately dense; without reticulate microsculpture; setae densely distributed, covering the surface; without macrosetae. Hind wings well developed. Mesocoxal acetabula margined posteriorly. Mesocoxal cavities not separated by meso- and metaventrite processes; mesoventrite process short (approx. 0.26 mm) with apex acuminate; metaventral process medium-sized (approx. 0.35 mm), marginate and with apex subobtuse; isthmus not present. Legs with tarsal formula 4–4–5, each apical tarsus with an empodium, one seta on empodium and a pair of tarsal claws, each claw with a subbasal tooth.

Abdomen. Abdomen fusiform (Fig. 1), narrower than elytra, although tergite VIII is modified to form a long horn; tergites with scarce setae; sternites with dense microsetae (Figs 8–9), but slightly less dense than elytra, almost without macrosetae on abdominal segments III-VI except on lateral margins of sternites; tergite VIII modified to form a long horn almost glabrous on dorsal surface, but with long setae on ventral surface, sparsely to slightly densely distributed. Tergite VII (Fig. 10) with lateral margin modified to form a structure-like wall on each side, which apparently provides support between tergite and sternite (only visible because of transparency on slides), and with an apical sclerotized plate attached internally (only visible because of transparency on slides) to receive tergite VIII (Fig. 11). Tergite VII has a small “U” incision on midline to receive the modified tergite VIII.

The new genus is very close to Placusa; however, it can be distinguished easily by tergite VIII, which is modified completely to form a horn, and the sclerotized lateral internal wall of tergite VII, that apparently supports tergite VIII. Tergite VII has a sclerotized internal plate in the posterior margin that may also support tergite VIII. Moreover, there are some differences in the median lobe of Placusa (crista apicalis shorter) and Placukorna (crista apicalis longer; Fig. 12) upon comparison. In addition, Placukorna shows lateral or ε-sensilla on the epipharynx, the medial field of epipharynx is not flanked by rows of large scales, and prementum with lateral field of pores with pseudopores extended from medial field. The same characters are useful for distinguishing the new genus from other Placusini. Another useful character for distinguishing Placukorna from Placusa is the absence of spine-like dents on the apex of tergite VIII that are present Placusa males.

Placukorna ipsa Santiago-Jiménez sp. n.

The genus name is a combination of “Placusa” and “korna”, from the Greek “Πλαξ” (meaning surface plane) and “κόρνα” (meaning horn), respectively.

Neuter.

Specimens were found in Lindgren and cross traps baited with ipsenol, ipsdienol and lanierone in a mixed pine forest. The forest is composed of Pinus pseudostrobus, P. montezumae and P. patula, located around 3090 m a.s.l.

Figure 15. 

Collection site of Placukorna ipsa Santiago-Jiménez gen. n. and sp. n. (black square).

The single described species, Placukorna ipsa, is known only from the Cofre de Perote volcano, in the central region of Veracruz state, in Mexico. Apparently, the genus is distributed in montane areas.

México: Veracruz, Perote, Ejido Agua de los Pescados, 3090 m a.s.l., 19°31'30"N, 97°07'00"W, mixed pine forest, Lindgren trap # 14, 08–15.V.2015, P. Domínguez, C. Ruíz and R. Santiago.

Holotype, male, pinned. Original label: “México: Veracruz, Perote, Agua de los Pescados. B. Pino mixto, 19°31'30"N, 97°07'00"W, 3086 m, tr. Lindgren #14, 08.V–15.V.2015, P. Domínguez, C. Ruíz, R. Santiago”/ “MUZ-UV-COL-00003446”/ HOLOTYPE Placukorna ipsa Santiago-Jiménez, 2016” [red label].

Paratypes, same data as holotype except for: tr. de cruz # 6 (1 specimen ♂); same data except for: tr. de cruz # 8 (1 specimen ♀); same data except for: tr. de cruz # 7, 20.III–27.III.2015 (1 specimen on slide ♂); same data except for: tr. Lindgren # 11, 27.III–03.IV.2015 (6 specimens: 2 ♀ on slide; 2 specimens ♂ and 2 specimens ♀); same data except for: tr. Lindgren # 13 (1 specimen ♂); same data except for: tr. Lindgren # 14 (2 specimens: 1 specimen ♀ and 1 specimen ♂); same data except for: tr. de cruz # 6 (2 specimens ♂); same data except for: tr. de cruz # 7 (2 specimens ♀); same data except for: tr. de cruz # 9 (1 specimen ♂); same data except for: tr. Lindgren # 14, 10.IV–17.IV.2015 (1 specimen ♂); same data except for: tr. de cruz # 8, 17.IV–24.IV.2015 (2 specimens: 1 specimen ♂ and 1 specimen ♀); same data except for: tr. Lindgren # 13 (1 specimen ♀); same data except for: tr. de cruz # 7, 24.IV–01.V.2015 (1 specimen ♂); same data except for: tr. Lindgren # 12 (1 specimen ♀); same data except for: tr. Lindgren # 14 (1 specimen ♂); same data except for: tr. de cruz # 9, 01.V–08.V.2015 (2 specimens ♀); same data except for: tr. Lindgren # 12, 15.V–22.V.2015 (1 specimen ♂). All specimens deposited in MUZ-UV under numbers MUZ-UV-COL-00003447 to 00003473 [yellow label].

Although for the moment it is the only one known species to the genus, it is distinguished by the following combination of characters: body length 2.5–3.0 mm; head and pronotum dark brown and abdomen black; apical half or apical third of sternites III-VI reddish brown; elytra dark brown to black; coxae dark brown to black; metatrochanter and metafemur dark brown or yellowish brown, remaining legs yellowish brown; antennomeres 1–11 dark brown; surface of tergites and sternites III–VII with reticulate microsculpture, less evident on tergites III–IV; tergites III–VII with basal impression, III–V almost straight, VI posteriorly slightly curved, VII posteriorly evidently curved; tergite VI with a protuberance on each side of midline; spermatheca with small and approximately spherical capsule, median portion of spermathecal stem (duct) narrowly U–shaped, and posterior portion also U–shaped, with accessory gland; median lobe with moderately large bulbus, tubus almost straight, internal sac of median lobe with evident spinules, apex blunt in lateral view, with short compressor plate (less than half of median lobe), basal ridge convex and pointed; flagellum short, without coils in bulbus; process of crista apicalis long, almost straight and parallel to median lobe, rounded at the apex.

Body length 2.5–3.0 mm. Head and pronotum dark brown and abdomen black; apical half or apical third of sternites III-VI reddish brown; elytra dark brown to black; coxae dark brown to black; metatrochanter and metafemur dark brown or yellowish brown, remaining legs yellowish brown. The apical edge of tergite III can be reddish.

Head. Dorsal surface without impression, protuberance or carina on disc (Fig. 4). Antennomeres 1–11 dark brown. Antennomeres 1–2 very long, 3 long, 4–10 transverse, and 11 long (Fig. 3).

Mouthparts. As described for the genus.

Thorax. As described for the genus.

Abdomen. As described for the genus. Other conspicuous characters are: surface of tergites and sternites III–VII with reticulate microsculpture, less evident on tergites III–IV; tergites III–VII with basal impression, III–V almost straight, VI posteriorly slightly curved, VII posteriorly evidently curved, and tergite VI with a protuberance on each side of midline.

Secondary sexual structures. There are differences between the sexes in the shape of sternite VIII and the number of macrosetae on it (Figs 8, 9). No other visible secondary sexual characters were found.

Female. Spermatheca with small and approximately spherical capsule, median portion of spermathecal stem (duct) narrowly U–shaped, and posterior portion also U–shaped, with accessory gland (Fig. 13).

Aedeagus. Median lobe with moderately large bulbus, tubus almost straight, internal sac of median lobe with evident spinules, apex blunt in lateral view, with short compressor plate (less than half of median lobe), basal ridge convex and pointed; flagellum short, without coils in bulbus (Fig. 12). Process of crista apicalis long, almost straight and parallel to median lobe, rounded at the apex (Fig. 12). Paramere with anterodorsal margin of paramerite with prominent sensory pores present beneath the velar sac (Fig. 14); hinge zone of paramerite evident, extended from dorsal surface to near articulation between condylite and paramerite; apical process of paramerite clearly articulated anterior to edge of velum; condylite with row of sensory pores; velum short (less than half length of paramere).

Placukorna ipsa is the only described species in the genus. The characters that could be useful at the species level are the shape of the aedeagus, spermatheca, and impressions and protuberances on the abdomen as described above.

Some characters that vary among the specimens collected are: protuberances on each side of midline of tergite VI are inconspicuous to prominent, one specimen had a raised midline from tergite III–VI, and the horn of tergite VIII is as long as tergite VII or tergites VI–VII together.

As the specimens were found associated with Scolytinae of the genera Ips DeGeer and Pseudips Cognato, the name makes reference to Ips from Greek “ἴψ” (meaning sort of worm), with Greek ending “a”.

Neuter.

Specimens of Placukorna are possibly living in galleries of Ips and Pseudips associated with different Pinus species of the mixed pine forest (Pinus pseudostrobus predominating) where they were collected. Specimens were collected using traps baited with a mix of semiochemicals (ipsenol, ipsdienol and lanierone), in which more than 180 specimens of Ips (94) and Pseudips (91) were also collected. The semiochemicals are commonly used in those traps to capture bark beetles (Scolytine), therefore, an association of specimens of Placukorna with Ips and Pseudips is plausible.

Placukorna ipsa sp. n. is known from the type locality in the central region of Veracruz, Mexico. Twenty-eight specimens of Placukorna ipsa sp. n. were captured by handmade intercept traps for bark beetles primed with the semiochemicals mentioned above, in mixed pine forest. The locality Agua de los Pescados is 3090 m a.s.l. on the northeast face of the Cofre de Perote, Veracruz, Mexico (Fig. 15).