Phaesticus mellerborgi

Phaesticus mellerborgi (Figs. 35–39) This species has 13- or 14-segmented antennae. Namely, in this species, as already reported by Zha et al. (2021), the third antennomere (first flagellar) may be divided into two small segments. Thus, the widest antennomere is the 8 th or the 9 th. The widest segment is elongated and ovoid in the cross-section in both base and apex. However, its apical cross-section has a wider perimeter. 7 th antennomere (Fig. 35, Fig. 36) is a bit narrower than the 8 th, 0.93 m long and 0.47 mm wide at the widest part and with an area on each side of about 0.35 mm 2. It is the second widest antennal segment in this species. Dorsal side fully covered in cuticular plates (each about 12 µm x 8 µm). Ventral side (Fig. 36) with 9-porous coeloconic field covering area of about 575 µm 2 and with about 5 µm of the pore diameter. The coeloconic field similar in shape to that of the 9 th segment, with two upper pores and 7 lower ones. No elongated placoid fields are situated on this antennomere and no basiconic sensilla on the antennal surface on any side. Small basiconic sensilla, with the base cone up to 30 µm long are however situated on the margins. 8 th antennomere (Fig. 37, Fig. 38) is the widest one. It is 0.84 mm long, 0.52 mm wide and with area of one side of about 0.35 m 3. Its dorsal part is fully covered in triangular cuticular plates (12 µm x 9 µm). Ventral part (Fig. 38) has a 4-porous coeloconic field covering an area of about 365 µm 2, each pore with diameter of about 5 µm2. The coeloconic field is situated in the apical part of the antennomere and has a single elongated placoid field (26 µm long, 10 µm wide) next to it. The area around these fields is smooth and does not bear cuticular plates. No modified basiconic sensilla were found on the antennal surface, but many small basiconic sensilla are present on the edge. The 9 th antennomere (Fig. 39) is 0.65 mm long, 0.28 mm wide at the widest part, and with an area of one side of about 0.15 mm 2 It is very similar in overall morphology to the previous two antennomeres, and looks on the first sight as a minute version of any of them. It is also covered in cuticular plates (12 µm x 8 µm). However, upon closer inspection it has a quite different set of traits. Its apical ventral side has, besides a 9-porous coeloconic field (covering about 630 µm 2 and with each of the pores with diameter from 3.5 µm to 5.5 µm), 11 large elongated placoid fields (each about 30 µm long, and about 8 µm wide). The area around the coeloconic and placoid fields is smooth. On each margin, there are small basiconic sensilla.