New records of the Bulgarian endemic species Pilemia serriventris Holzschuh, 1984 (Cerambycidae: Lamiinae)

: Bulgarian endemic species Pilemia serriventris (Holzschuh, 1984) is reported for the first time with exact data from several localities, including its type locality near Harmanli. The species is distributed in SE Bulgaria along river valleys from the Aegean and the Black Sea drainage basins, inhabiting both riverside and roadside habitats. The host plant of the species appears to be Anchusa procera Besser, and the earlier reports of host plants are doubtful.

In the present work we report several new localities of the species in SE Bulgaria, as well as a new data on the host plants of the species.

Methods
The material for the present study was collected by the authors in the period 2018 -2023 from Eastern Rhodopes Mts, Maritsa River Valley and Strandzha Mts (Fig. 1).Adult beetles were hand collected from the host plants.The pictures were taken by using digital camera Olympus SP-820UZ (Fig. 1C), Canon PowerShot SX420 IS (Fig. 1A, B, D-F, Fig. 2) and a combination of Canon EOS 2000D digital camera, PRO-CA Camera Adapter, and a microscope Olympus SZ61 .The collected specimens are preserved in the Zoological Collection of Sofia University, Faculty of Biology (BFUS).

Results and discussion
Pilemia serriventris (Holzschuh, 1984) Material: Maritsa Riv.Valley, Lyubimets, right bank of Maritsa Riv. (Fig. 1A  All specimens were collected from the host plant Anchusa procera Besser (Fig. 2).On the same plant species, the process of copulation, as well as feeding on flower petals, were observed.The records of C. hungaricum Simonk., but we did not observe individuals of P. serriventris on this plant species.Anchusa barrelieri, which was reported as a host plant of P. ser-riventris from Bistrets (Georgiev et al., 2005) was not found in the vicinity of this village during the present study, as well as nowhere else in the areas visited.
According Holzschuh (1984) and Bense (1995), the longitudinal rows of ocher (yellowish-brown) hairs on the elytra in both sexes, median tooth-like processes on the abdominal sternites 1 and 2 in males as well as the regularly sharpened apex of penis are among the main diagnostic features of P. serriventris (Figs 3, 4, 5A, 6A).In some examined specimens of P. serriventris, however, the longitudinal rows on the elytra are less pronounced to almost invisible.On the other hand, such rows are well developed in some of the P. tigrina specimens in the populations of the Western Stara Planina Mts (Gradinarov, 2016;Gradinarov & Petrova, 2019), as well as in populations of P. tigrina in Romania (Crișan et al., 2017).Among the males of P. tigrina from the locality of the species in the region of Beledie han (Gradinarov & Petrova, 2021) specimens with welldeveloped processes on the abdominal sternites 1 and 2 can also be found (Fig. 5B).Thus, the shape of the apex of penis is the most useful character for distinguishing P. serriventris (Fig. 6A, B) and P. tigrina (Fig. 6C, D).The pygidium in males of P. serriventris is significantly wider distally than in P. tigrina, which can also be used in distinguishing the two species (Holzschuh, 1984).
Roots of A. procera with live Cerambycidae larvae were collected on 9 September 2021, and April  16, 2023, from the locality near Lyubimets and that near Kotlari Vill., respectively.In both cases, single specimens of Phytoecia (Opsilia) coerulescens (Scopoli, 1763) (Cerambycidae: Lamiinae) have emerged from the roots after laboratory rearing.The last species is polyphagous mostly in Boraginaceae (Sama, 2002) and has been reported together with P. tigrina on A. barrelieri by earlier authors (Kovács, 2005;Crișan et al., 2017).
In our study, adults of P. serriventris were found on the host plants in the period of the second half of May to the beginning of June.Our data is consistent with the known period of activity of the adults of this species (Holzschuh, 1984;Georgiev et al.;2005,   Historia naturalis bulgarica 46 (2024) Hoskovec et al., 2023).Adults of P. serriventris appear to become active later in spring than those of P. tigrina, which in Bulgaria can be found on food plants already in April (Gradinarov 2016;Gradinarov & Petrova, 2019;2021).The late appearance of the adults of P. serriventris is probably related with the late flowering of the host plant A. procera, in comparison to A. barrelieri.
During the survey we found the species at an altitude of about 50 to 170 m. a.s.l., on alluvial banks of rivers from the Aegean drainage basin (Maritsa Riv., Arda Riv., Biserska Reka Riv.) and from the Black Sea drainage basin (Sredetska Reka Riv.).Near Lyubimets and near the Prohod Vill., it was also found among roadside vegetation at a greater distance (up to about 120 m) from the river.Both habitat types belong to the linear habitats (with linear strips of vegetation) sensu Bennett (2003).The second species of the subgenus Pilemia in Bulgaria -P.tigrina, has been recorded from linear habitats as well (Gradinarov & Petrova, 2021).In such habitats natural vegetation may have remained intact and they can serve as corridors for the dispersal of plant and animal species (Bennett, 2003).The presence of P. serriventris along the rivers Arda and Maritsa is also possible in the neighboring areas of Greece and the European part of Türkiye.
officinale and A. barrelieri as host plants of P. serriventris, by Rejzek et al. (2001) and Georgiev et al. (2005) respectively, are rather doubtful.In the localities near Kotlari and Slavyanovo, A. procera Besser coexist with other species of genus Cynoglossum -C.