Placukorna Santiago-Jimenez

Santiago-Jimenez, Quiyari J. & Santiago-Navarro, Rosny, 2016, A new genus and species of Placusini from a high mountain in Mexico, ZooKeys 640, pp. 45-57 : 46-49

Placukorna Santiago-Jimenez gen. n.

Diagnosis.

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.

Description.

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).

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.

Remarks.

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.

Type species.

Placukorna ipsa Santiago-Jiménez sp. n.

Etymology.

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

Gender.

Neuter.

Habitat.

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 , Pinus montezumae and Pinus patula , located around 3090 m a.s.l.

Distribution.

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.

Identification key to the genera of Placusini