taxonID	type	description	language	source
784987B8FA3E6B71FD3190BFFBC0A219.taxon	materials_examined	Type material: BULGARIA: Holotype: 1 ♀ ‘ Šarlir, Pirin, Mac. VII. 32, Mař & Táb. ’ (NMPC); Paratype: 1 ♀ ‘ Samokov, M. Hilf 1911, coll. O. Leonhard’ (NMPC). Additional material examined: T. bohemorum BULGARIA: 1 ♀ ‘ Šarlir, Pirin, Mac. VII. 32, Mař & Táb’ (NMPC); 1 ♂ ‘ BG Zemen Gorge, N 42.450278 E 22.708611, 23. X. 2000, 583 m a. s. l., leg. D. Gradinarov’ (BFUS-CAR 000001); T. kobingeri Apfelbeck, 1902 ALBANIA: 1 ♂ ‘ Shkoder, m. e. Cukalit m-t, 1300 m, 27. VI. 2001, P. Moravec lgt. ’ (PMLC); T. kobingeri pawlowskianus BULGARIA: 2 ♂♂ ‘ Rilo Dagh., Collectio de Obenberger, Mus. Pragense’ (NMPC); T. pirinicus Pawlowski, 1972 1 ♂ ‘ BULGARIA mer., Pirin b., 3. VI. 1998, Kalugera Cerna gora, 1600 – 1800 m n. m., L. Mencl lgt. ’ (PMLC); T. merkli Pawlowski, 1973 BULGARIA: 1 ♂ ‘ Stara planina, Berkovska pl.: Kom hut, 1650 m 23. VII. 2000, P. Moravec lgt. ’ (PMLC); 1 ♂ same as previous but 24. VII. 2000 (PMLC) BULGARIA: 1 ♂ ‘ bor, Stara planina, Kom: 1700 – 2000, 17. VI. 1996, Libor Klima lgt. ’ (PMLC); T. obtusiusculus Ganglbauer, 1889 MONTENEGRO: 1 ♂ ‘ Durmitor Mont, Savin Kuk, 2000 m, 30. VI. 1958, Mař. Hoberl. lgt. ’ (NMPC); T. zarandicus Moravec, 1986 ROMANIA: holotype: 1 ♂ ‘ Mt. Zarand: vf. Drocea-Madrigesti, 17. VII. 1984, 400 – 600 m, P. Moravec lgt. ’; paratypes: 2 ♀♀ same as previous (PMLC).	en	Kostova, Rumyana, Bekchiev, Rostislav (2025): New insights into the taxonomy of Trechus Clairville, 1806 (Coleoptera: Carabidae) in the Balkans, with the first description of the male of Trechus bohemorum Pawlowski, 1973. Zootaxa 5661 (4): 538-552, DOI: 10.11646/zootaxa.5661.4.4, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
784987B8FA3E6B71FD3190BFFBC0A219.taxon	discussion	Despite being described from female specimens, T. bohemorum has quite distinct diagnostic characters — its elytra shape (elongated with slightly arcuated sides) and the presence of wings (Pawlowski 1973). In the zoological collection of Sofia University BFUS, a male specimen of the “ obtusiusculus ” group was deposited that has characters matching the description of T. bohemorum. The material was compared with female type specimens of T. bohemorum of deposited at the NMPC. In addition to the two specimens described by Pawlowski (1973), a third female specimen of the species bearing the same label as the holotype was found and identified by Pavel Moravec in 1997 in the NMP collection. We found that the male specimen from the BFUS collection matches morphologically both the type series and the description with illustrations of the habitus by Pawlowski (1973). Thus, this specimen represents the first documented male of T. bohemorum.	en	Kostova, Rumyana, Bekchiev, Rostislav (2025): New insights into the taxonomy of Trechus Clairville, 1806 (Coleoptera: Carabidae) in the Balkans, with the first description of the male of Trechus bohemorum Pawlowski, 1973. Zootaxa 5661 (4): 538-552, DOI: 10.11646/zootaxa.5661.4.4, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
784987B8FA3E6B71FD3190BFFBC0A219.taxon	diagnosis	Diagnosis T. bohemorum differs from the other representatives of the T. “ obtusiusculus ” group in less elongated median lobe of male genitalia without clear constriction near basal bulb, straight and rather wide distal portion in dorsal view, and small button-like apex in lateral view. Additionally, it differs from most representatives of the group in elongate habitus with parallel-sided elytra widest in apical third (EL / EW = 1.4 ÷ 1.5; L / EL = 1.5 ÷ 1.7), a short and broad pronotum (PW / PL = 1.3 ÷ 1.6), and the presence of well-developed wings (Fig. 1). The median lobe of the aedeagus in T. bohemorum, is similar to that of T. kobingeri pawlowskianus but differs in the basal bulb, with no narrowing at the place of junction with the main part in T. bohemorum. The bended upward tip of the apical part is also smaller in T. bohemorum in relation to T. kobingeri pawlowskianus, and the copulatory piece distally ends with a very small, thick spine in T. bohemorum (Fig. 2). In addition, T. kobingeri pawlowskianus is wingless, the elytra are shorter, and the lateral margins of the elytra are more oval, while T. bohemorum has well-developed wings and more parallel elytra margins. In terms of elytral proportions, T. bohemorum resembles T. cephalonicus Winkler, 1914 but differs in the shape of the posterior angles of the pronotum, less pointed and projected in the former than in the latter. T. bohemorum also clearly differs from T. cephalonicus in the shape and internal structure of the aedeagus, which in the latter is clearly narrowed near the basal bulb, with much larger, strongly upward curved apical disc tip in lateral view and copulatory piece with long, protruding apical part. The variation in the metric characters and indices of the studied specimens are shown in Table 1.	en	Kostova, Rumyana, Bekchiev, Rostislav (2025): New insights into the taxonomy of Trechus Clairville, 1806 (Coleoptera: Carabidae) in the Balkans, with the first description of the male of Trechus bohemorum Pawlowski, 1973. Zootaxa 5661 (4): 538-552, DOI: 10.11646/zootaxa.5661.4.4, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
784987B8FA3E6B71FD3190BFFBC0A219.taxon	description	Description of the male Body length 3.6 mm. Colour: dark brown; antennae, legs, and mouthparts paler, as in holotype. Microsculpture isodiametric, well visible at the head, pronotum and elytra base at magnitude 50 ×, disc shiny. Habitus as in Fig. 1. Head: Maximum head width (0.78 mm) at level of eyes, which are well-developed. Antennae reaching anterior third of elytra. Pronotum: Transverse (PW / PL = 1.47), subcordate, with maximum width in first third; Lateral sides rounded anteriorly, slightly sinuate posteriorly, posterior angles obtuse with clearly visible protruding denticles (PW / PBW = 1.19). Basal margin protruding medially. Marginal setae: One in anterior third and one at posterior angle on each side. Elytra: Elongate, almost parallel with maximum width in apical third, elytral apex with a prominent tooth near suture (EL / EW = 1.51). Striae 1 – 4 clearly visible, deeper in basal half and shallower towards apex. Only stria 1 deeply impressed along its entire length. Remaining striae obsolete, progressively fading laterally. Two discal setae on third interval close to third stria. Lateral marginal (umbilical) series consisting of four humeral setae, concentrated and narrowly spaced in basal third, and 2 + 2 setae widely spaced in posterior two-thirds. Reverse apical stria well-developed up to half of elytra apical third. Hind wings well-developed. Male genitalia: Median lobe in lateral view, bent at nearly right (slightly obtuse) angle distal to basal bulb. The apical portion attenuate ventrally, ending in a distinct apical disc tip curved upward (see lateral and dorsolateral views in Fig. 2). The copulatory piece relatively long, triangular-shaped in lateral view, broad basally and pointed and slightly bent upward apically, distally ending with a miniature spine. Endophallus with hairy areas.	en	Kostova, Rumyana, Bekchiev, Rostislav (2025): New insights into the taxonomy of Trechus Clairville, 1806 (Coleoptera: Carabidae) in the Balkans, with the first description of the male of Trechus bohemorum Pawlowski, 1973. Zootaxa 5661 (4): 538-552, DOI: 10.11646/zootaxa.5661.4.4, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
784987B8FA3E6B71FD3190BFFBC0A219.taxon	biology_ecology	Habitat Small riparian meadow along the Struma River surrounded by deciduous forest. Collected manually by soil sampling.	en	Kostova, Rumyana, Bekchiev, Rostislav (2025): New insights into the taxonomy of Trechus Clairville, 1806 (Coleoptera: Carabidae) in the Balkans, with the first description of the male of Trechus bohemorum Pawlowski, 1973. Zootaxa 5661 (4): 538-552, DOI: 10.11646/zootaxa.5661.4.4, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
784987B8FA3E6B71FD3190BFFBC0A219.taxon	distribution	Geographical distribution The known collecting localities are situated in southwestern Bulgaria, relatively distant from each other. There is also a big difference in their altitudes from 2172 m a. s. l. (‘ Šarlir’, possibly a misspelling of the Sharaliya peak in the Pirin Mts.) to 583 m a. s. l. (Zemen Gorge) (Fig. 3). However, the retention of functional wings is a prerequisite for a broader distribution.	en	Kostova, Rumyana, Bekchiev, Rostislav (2025): New insights into the taxonomy of Trechus Clairville, 1806 (Coleoptera: Carabidae) in the Balkans, with the first description of the male of Trechus bohemorum Pawlowski, 1973. Zootaxa 5661 (4): 538-552, DOI: 10.11646/zootaxa.5661.4.4, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
784987B8FA3E6B71FD3190BFFBC0A219.taxon	discussion	Systematic position The presence of functional wings in T. bohemorum — unique character among group members — led Pawlowski to consider it a basal species of the group (Pawlowski 1973). The relatively simple archaic morphology of the median lobe — its medium size and small apical disc — is consistent with this interpretation.	en	Kostova, Rumyana, Bekchiev, Rostislav (2025): New insights into the taxonomy of Trechus Clairville, 1806 (Coleoptera: Carabidae) in the Balkans, with the first description of the male of Trechus bohemorum Pawlowski, 1973. Zootaxa 5661 (4): 538-552, DOI: 10.11646/zootaxa.5661.4.4, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
784987B8FA3A6B71FF3A95E4FC9BA706.taxon	materials_examined	Material studied: CROATIA: 1 ♂ labelled as T. pilisiensis Csiki, 1918 ‘ Zagreb, Tuskanac Zelengaj, 21. V. 1912 Cro. ’ (NMPC); SLOVENIA: 4 ♂♂ labelled as T. pilisiensis ‘ Radoha, Carn., Mařan lgt. ’ (NMPC); BOSNIA AND HERZEGOVINA: 1 ♂ labelled as T. goleshnicensis Apfelbeck, 1918 ‘ Bosnia, Ostrelj’ (NMPC).	en	Kostova, Rumyana, Bekchiev, Rostislav (2025): New insights into the taxonomy of Trechus Clairville, 1806 (Coleoptera: Carabidae) in the Balkans, with the first description of the male of Trechus bohemorum Pawlowski, 1973. Zootaxa 5661 (4): 538-552, DOI: 10.11646/zootaxa.5661.4.4, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
784987B8FA3A6B71FF3A95E4FC9BA706.taxon	discussion	Examination of the male genitalia of the above-mentioned specimens in the collection of the NMPC revealed that all of them belong to T. cardioderus sensu stricto. The morphology of the median lobe in these specimens does not match identification labels, as all have a strongly downward-curved apex (Fig. 7), which is characteristic of T. cardioderus s. str. (Jeannel 1927: 455 Fig. 1077). Until now, the nominative subspecies of T. cardioderus was known only from Romania and North Macedonia (Jeannel 1927; Nonveiller 1994; Hristovski & Guéorguiev 2015; Belousov 2017). Thus, the nominative subspecies of T. cardioderus is recorded for the first time in Croatia, Slovenia, Bosnia and Herzegovina (Fig. 4). New labels with revised identifications were pinned beneath the specimens.	en	Kostova, Rumyana, Bekchiev, Rostislav (2025): New insights into the taxonomy of Trechus Clairville, 1806 (Coleoptera: Carabidae) in the Balkans, with the first description of the male of Trechus bohemorum Pawlowski, 1973. Zootaxa 5661 (4): 538-552, DOI: 10.11646/zootaxa.5661.4.4, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
784987B8FA3A6B71FF6A92EEFE3FA556.taxon	description	Taxa of the “ subnotatus ” group are known for their high variability in diagnostic characters, with many intermediate forms difficult for identification, particularly at the subspecies level (Jeannel 1927; Pawlowski 1973; Hieke & Wrase 1988; Kostova & Bekchiev 2023). Study of the “ subnotatus ” group material in the Coleoptera collection of NMPC yielded new taxonomic insights and new data on the distribution of two T. cardioderus subspecies, based on their revised identification.	en	Kostova, Rumyana, Bekchiev, Rostislav (2025): New insights into the taxonomy of Trechus Clairville, 1806 (Coleoptera: Carabidae) in the Balkans, with the first description of the male of Trechus bohemorum Pawlowski, 1973. Zootaxa 5661 (4): 538-552, DOI: 10.11646/zootaxa.5661.4.4, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
784987B8FA3A6B70FF3A9754FCD3A792.taxon	materials_examined	Material studied: GREECE: 2 ♂♂ ‘ Janina- IV. 1927, Grecia, Dr. Purkyně’ (NMPC); 1 ♂ ‘ Kephallenia, Paganetti, col. Kouřil’ (NMPC); 1 ♂ labelled as T. subnotatus ‘ Attica, Reitter, col. Kouřil’ (NMPC); MONTENEGRO: 1 ♂ ‘ Jaz u Budvy, 5. VI. 67, Mařan lgt. ’ (NMPC); 1 ♂ labelled as Trechus subnotatus athonis: Bocca di Cattaro, Rittm. Matcha, col. Kouřil’ (NMPC); 1 ♂ ‘ Topla, Paganetti’ (NMPC); BOSNIA AND HERZEGOVINA: 1 ♂ ‘ Saraievo, V. M. Duchoň’ (NMPC); BULGARIA: 1 ♂ ‘ Šarlir Vrch, Pyrin plan., Bulgaria, B. Kuřil’ (NMPC), 1 ♂ ‘ Šarlir Pirin, Mac. VII 32, Mař. et Táb’ (NMPC).	en	Kostova, Rumyana, Bekchiev, Rostislav (2025): New insights into the taxonomy of Trechus Clairville, 1806 (Coleoptera: Carabidae) in the Balkans, with the first description of the male of Trechus bohemorum Pawlowski, 1973. Zootaxa 5661 (4): 538-552, DOI: 10.11646/zootaxa.5661.4.4, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
784987B8FA3A6B70FF3A9754FCD3A792.taxon	discussion	The study of the male genitalia showed that all the above-mentioned specimens belong to the subspecies T. cardioderus athonis. The median lobe of the aedeagus in all males is with a copulatory piece strongly arcuate distally, and the apex of the median lobe slightly curved downwards (Fig. 7, J – O). The specimen from Attica does not match T. subnotatus, as it was labelled, which according to Jeannel has a median lobe of the male genitalia with an almost straight copulatory piece in lateral view (Jeannel 1927: 443 Fig. 1051). In the present specimen, however, it is strongly curved upwards in the apical part. The two specimens from Šarlir (as it was already noted, most likely a misspelling of Sharaliya peak, Pirin Mts.) in Bulgaria, reported by Mařan (1933) as T. cardioderus goleshnicensis and by Pawlowski (1973) as T. subnotatus, with copulatory apparatus slightly different from that described by Jeannel (1927), perfectly match the diagnostic characters of T. cardioderus athonis. At the same time, they differ from both T. subnotatus and the morphologically closer T. cardioderus goleshnicensis. The latter, under Jeannel’s concept, is characterised by a straight apex of the median lobe in lateral view (Jeannel 1027: 455 Fig. 1078). Consequently, the assumption proposed by Kostova and Bekchiev (2023) about the lack of T. cardioderus goleshnicensis in the Bulgarian fauna is confirmed. T. cardioderus athonis was previously known from Greece, North Macedonia, and Bulgaria (Jeannel 1927; Nonveiller et al. 1994; Hristovski & Guéorguiev 2015; Belousov 2017; Kostova & Bekchiev 2023). New subspecies records are: Bosnia and Herzegovina — Sarajevo; Montenegro — Budva env., Bocca di Cattaro (Bay of Kotor), and Topla — Castelnuovo (Herceg novi) env.; Greece — Ioannina env. and Cephalonia Isle (Fig. 5). Thus, this study provides the first confirmed records of T. cardioderus athonis for Montenegro and Bosnia and Herzegovina. Giving the current known distribution, it is highly probable that T. cardioderus athonis could also be found in Albania. New labels with revised identifications were pinned beneath the specimens.	en	Kostova, Rumyana, Bekchiev, Rostislav (2025): New insights into the taxonomy of Trechus Clairville, 1806 (Coleoptera: Carabidae) in the Balkans, with the first description of the male of Trechus bohemorum Pawlowski, 1973. Zootaxa 5661 (4): 538-552, DOI: 10.11646/zootaxa.5661.4.4, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
784987B8FA3B6B7BFF3A97D8FAEDA0F1.taxon	materials_examined	Material studied: T. cardioderus cardioderus above mentioned six specimens and ROMANIA: 1 ♂ ‘ Flaischar, Orszova’ (NMPC); T. cardioderus athonis above mentioned ten specimens (NMPC); T. cardioderus balcanicus Jeannel, 1927: AUSTRIA: 1 ♂ ‘ Rotenturum / P. Deubel’ (NMPC); BOSNIA AND HERZEGOVINA: 1 ♂ ‘ Bosnien, Mt. Igman 1400 m, Sarajevo, 16. V. 1990 Battoni’ (BFUS); 1 ♂ ‘ Bosnia, Trebević, V. 1907 ’ (NMPC); 1 ♂ ‘ Hercegovina, Tara pl., Babina gora, 01. VI. 1967, Mařan’ (NMPC), 1 ♂ ‘ Bosna, Treskavica, 1200 – 1500, 19. VII. 1974, K. Hůrka’ (NMPC); BULGARIA: 1 ♂ ‘ Stara Planina, Chumen les, 1250 – 1400 m, 19. VII. 1987, leg. K. Hůrka’ (NMPC); 1 ♂ ‘ Stara planina, Bukovec env. Les, potok, 900 – 1000 m, 20. VII. 1987, K. Hůrka’ (NMPC); 1 ♂ ‘ Stara Planina, Chumerna les 1300 – 1400 m, 21. VII. 1987, K. Hůrka’ (NMPC); 1 ♂ ‘ St. Planina, El. Tvard., Planina, les 18. VII. 1987, leg. K. Hůrka’ (NMPC); 1 ♂ ‘ Stara planina, Berkovska pl. Kom hut, 1650 m, 23. VII. 2000, P. Moravec lgt. ’ (BFUS); 1 ♂ ‘ Stara planina, Berkovitsa-Kom hut, 1000 – 1200 m, 25. VII. 2000, P. Moravec lgt. ’ (BFUS); 1 ♂ ‘ Stara planina, Gorni Lom-mt. Midzhur, 100 – 1500 m, 27. VII. 2000, P. Bulirsch’ (BFUS); CROATIA: 1 ♂ ‘ Krajina, 05. IV. 1905 ’ (NMPC); ROMANIA: 1 ♂ ‘ Mt. Căpătânii, Cheile Oltețului-Polovragi, 650 m, 17. VI. 1998, P. Moravec lgt’.; 5 ♂♂ same as previous but 650 – 800 m (BFUS); 2 ♂♂ ‘ Mt. Căpătânii, valea Cheia, vf. Stogsoare, env., 750 – 900 m, 6 – 7. VII. 1999, P. Moravec lgt. ’ (BFUS); 1 ♂ ‘ Mt. Căpătânii, valea Cheia, I. F. Luncile, Oltetului env., 650 m, 8. VII. 1999, M. Jaros lgt. ’ (BFUS); 1 ♂ ‘ Muntii Fagaraf Ului, Biela Cascada, 2200 m, VIII. 97, lgt. Snizek’ (BFUS); SERBIA: 1 ♂ ‘ Jugoslavija, Serbia, Maljen, Divcibare-sedlo, 750 – 900 m, 20. V. 1991, P. Moravec lgt’ (BFUS); 1 ♂ same as previous but 700 – 800 m, 19. V. 1991 (BFUS); SLOVENIA: 1 ♂ ‘ Sv. Lovrenc, VII. 1934 ’ (NMPC); 1 ♂ ‘ Bor. mont., Ožbalt 5 – 6. X. 2002, J. Bednář lgt. ’ (BFUS); 2 ♂♂ ‘ Kobansko, Hude luknja env., u potoka, pr. Radlje ob Dravi, 7. V. 1992, R. Mlejnek lgt. ’ (BFUS). T. pilisensis pilisensis Csiki, 1918: AUSTRIA: 2 ♂♂ ‘ Schoberstein, Austr. Sup, Mont. Petz ,, coll. Lokay’ (NMPC); 1 ♂ ‘ Wein, Umg. Rekawinkel, coll. Lokay’ (NMPC); CZECHIA: 1 ♂ ‘ Boh. Krkonose Obri dul, 27. VII. 1956, Hůrka’ (NMPC); 1 ♂ ‘ Boh. Sumava, Stozec-les, 2. V. 1987, K. Hůrka ’ (NMPC); 2 ♂♂ ‘ M. bor. 8. IX. 1969, Dolni Morava, Mlynar lgt. ’ (NMPC); HUNGARY: 1 ♂ ‘ Hung. mer. Mecsek Mlsinateo, 26. V. 1964, Hůrka’ (NMPC); SLOVAKIA: 1 ♂ ‘ Slov. Or. Hrubku, potok, 700 – 600 m, 10. VII. 1961, Hůrka’ (NMPC); SLOVENIA: 1 ♂ ‘ Kalobje, 30.11.1928, coll. Lokay’ (NMPC); T. binotatus Putzeys, 1870: ITALY: 1 ♂ ‘ Vallombrosa’ (NMPC); T. asiaticus Jeannel, 1927: BULGARIA: 1 ♂ ‘ Strandzha pl, Bulg., VII. 34 Pfeffer’ (NMPC); 4 ♂♂ ‘ Zeitinburun (= Maslen nos), Bulg. Orient., VI. 33 Mař. Táb’ (NMPC); TURKEY: 2 ♂♂ ‘ Bursa, Asia Min., Dr. Jurecek 1931 ’ (NMPC); 1 ♂ ‘ Suluhan, Toros, Anat. 11. VII. 1947, Exp. N. Mus. ČSR’ (NMPC); T. byzantinus Apfelbeck, 1901: TURKEY: ‘ Belgrada. Wal., Turkei, ex. coll. Paganetti, coll. Kouřil’ (NMPC). The newly obtained morphometric data were pooled with the previous sample of Kostova and Bekchiev (2023), containing data for T. cardioderus irenis Csiki, 1912 (36 ♂♂); T. cardioderus athonis (58 ♂♂); T. cardioderus balcanicus Jeannel, 1927 (5 ♂♂); T. asiaticus Jeannel, 1927 (4 ♂♂); T. strandzhensis Kostova & Bekchiev, 2023 (19 ♂♂); T. byzantinus 3 ♂♂; T. asiaticus (4 ♂♂).	en	Kostova, Rumyana, Bekchiev, Rostislav (2025): New insights into the taxonomy of Trechus Clairville, 1806 (Coleoptera: Carabidae) in the Balkans, with the first description of the male of Trechus bohemorum Pawlowski, 1973. Zootaxa 5661 (4): 538-552, DOI: 10.11646/zootaxa.5661.4.4, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
784987B8FA3B6B7BFF3A97D8FAEDA0F1.taxon	discussion	The pooled dataset (n = 191 males) was subjected to canonical stepwise discriminant analysis to assess morphological relationship among the studied taxa. Fig. 6, presents the results of this analysis. As was expected, there was a high degree of overlap and gradient distribution but also some ordering along the gradient of the taxa studied. The first canonical discriminant function accounted relatively small amount of the variation between groups — 49 %, canonical correlation coefficient Rc = 0.68, Wilks’ Λ = 0.26, χ ² (df. 35) = 249.73, p <0.001. The extremes of the gradients along the first canonical function are occupied by T. asiaticus and T. strandzhensis. The second canonical function explained 35 % of the variation, canonical correlation coefficient Rc = 0.61, Wilks’ Λ = 0.48, χ ² (df. 24) = 135.94, p <0.001. The ordering of the centroids was T. byzantinus, T. cardioderus athonis, T. asiaticus, and T. strandzhensis, from the one side and the very close centroids of T. cardioderus sensu stricto, T. cardioderus balcanicus, T. cardioderus irenis, and T. pilisensis pilisensis from the other (Fig. 6). The indices that remained in the analysis with the highest relevance for the discrimination were L, PW / PBW, EW / PW, EL / EW, L / PW, showing the body size, pronotum width and elytra length and width relations as key characters for taxa delimitation. However, they did not have a good discriminant value, with the cross-validation analysis showing that only 53 % of the group specimens were correctly classified. The highest error was for T. byzantinus, where all of the four specimens were classified as T. cardioderus athonis. followed by T. pilisensis, where 50 % of specimens were classified as T. cardioderus irenis, 30 % as T. cardioderus athonis and the rest as T. cardioderus balcanicus, and by T. cardioderus cardioderus, where 43 % of specimens were classified as T. cardioderus balcanicus and the rest as T. cardioderus athonis (28.6 %) and T. cardioderus irenis (28.6 %) (Table 2). These data demonstrate that misidentification is highly probable, when based exclusively on external morphology. The identification key for the T. “ subnotatus ” group by Jeannel (1927) is based mainly on the size, shape and colour of the pronotum and elytra. Our study demonstrates that reliable identification based exclusively on exterior characters — without male genitalia morphology — is nearly impossible. Furthermore, even the morphology of the median lobe may exhibit variations, introducing uncertainty in the determination of the group’s taxa. Fig. 7 presents comparative series of the median lobes of these taxa, all possessing a curved copulatory piece, demonstrating gradual morphological transitions among taxa. With additional material on the “ subnotatus ” group from the Balkans, the documented variation in the male genitalia morphology will likely expand, particularly among the subspecies of T. cardioderus. Even now, we found that the morphology of the median lobe of the T. pilisensis specimens in the NMPC collection (Fig. 7: G – I) does not correspond exactly to the drawing by Jeannel (1927: 453 Fig. 1075). In these specimens, the apical part of the aedeagus is slightly curved ventrally, similar to that of T. cardioderus transdanubiensis Nonveiller, Pavićević, Popović, 1994 described and, to date, reported only from Serbia (Nonveiller et al. 1994: 14 Figs. 5 – 6). Nonveiller et al. (1994) did not make a drawing of the copulatory piece of the median lobe, nider describe it in their paper. We assumed that if there is a differentiating character between them, it should be that the copulatory piece. However, this is an assumption for now, and uncertainty remains until the types of both taxa are studied and a clear difference is described. The present study of the collection at the NMPC has extended the data for T. cardioderus athonis, T. cardioderus goleshnicensis, and T. subnotatus subnotatus obtained in our previous studies of the collections at the MNHN (coll. Jeannel), SDEI, HNHM, NMNHS and BFUS. Our morphological studies reveal no consistent diagnostic differences among these three taxa due to their extensive variability, suggesting they will be likely synonymized in the future. The diagnostic characters given by Jeannel (1927) to distinguish these three taxa have become unreliable due to increasing overlap with larger sample sizes. Similarly, the original descriptions of these taxa lack taxonomic precision to rely on. The three taxa share the following characters: a relatively large, transverse pronotum with oval lateral margins, shortly and slightly sinuate before the small, nearly straight and only slightly protruding posterior angles; elongate elytra with maximum width at the second half of the elytra; reduced posterior wings; median lobe of male genitalia with prolonged apex in lateral view, and wide, straight apical lamella (not or only slightly narrowing) in dorsal view. The colouration of the elytra in T. cardioderus athonis and T. subnotatus varies (monocoloured, with humeral elongate spots and / or two anteriorly rounded spots). According to Jeannel (1927), the diagnostic differences between T. cardioderus athonis and T. cardioderus goleshnicensis are in the apex of the aedeagus in lateral view (slightly curved ventrally in the former and straight in the latter) and a very narrow pronotum in T. cardioderus goleshnicensis. Between them and T. subnotatus, he pointed only one difference in the copulatory piece of the median lobe, having a strongly upward-curved distal part in T. cardioderus athonis and T. cardioderus goleshnicensis while almost straight copulatory piece in T. subnotatus. We revealed that, all examined specimens from the Balkans in the studied collections previously labelled as T. cardioderus goleshnicensis or T. subnotatus turned out to be T. cardioderus athonis, according to the criteria of Jeannel (1927). The ratio of the width of the prothorax to the width of the elytra (EW / PW) varies strongly in the specimens of our T. cardioderus athonis sample. The EW / PW index ranges from 1.56 to 1.60 in the specimens from the type series (4 ♂ GREECE, Athos, SDEI), as well as from 1.39 to 1.69 in the total Balkan sample and it overlaps with that of the four specimens identified as T. cardioderus goleshnicensis by Jeannel in his collection (2 ♂♂ MONTENEGRO, Zljeb planina, 2 ♂♂ Besina gora Bielasica (MNHN, coll. Jeannel) with EW / PW ranging from 1.43 to 1.44 as was shown in our previous study (Kostova & Bekchiev 2023). The diagnostic value of the straight apex of the median lobe in lateral view in T. cardioderus goleshnicensis also remains uncertain due to the previous finding of syntopic specimens of T. cardioderus athonis from the Belasitsa Mts. in Bulgaria, with variations from curved downwards to straight apex in lateral view (Kostova & Bekchiev 2023). The upward curvature of the distal part of the copulatory piece of the median lobe, a differential characteristic between T. cardioderus subspecies and T. subnotatus, is also sometimes difficult to discern with certainty, especially in lateral view on microscope slides due to frequent displacement and rotation. Figure 8 shows variation in the median lobe (mounted on microscopic slides) of specimens identified by Jeannel as T. subnotatus subnotatus (Zelinica, Dalmatia; Cephalonia; Pesio) and T. subnotatus pallidipenis (Athica) — from his collection at MNHN. Despite the compromised quality of the slides and the fixed lateral positioning, the similarity between the aedeagus of T. subnotatus and T. cardioderus athonis is clearly observable. Additionally, the upwardly curved distal part of the copulatory piece in T. subnotatus pallidipenis — described as an unicolorous variant and now junior synonym of T. subnotatus — can be seen. However, at this stage of our research, we cannot be confident in our hypothesis that the three taxa represent a single, highly variable species, nor can we resolve the uncertainty regarding the specific independence of T. cardioderus. Further studies are needed based on more extensive material, especially from Greece and Macedonia, and fresh ethanol-preserved specimens from the entire ‘ subnotatus’ group range for combined morphological and molecular analysis of species boundaries and phylogenetic relationships.	en	Kostova, Rumyana, Bekchiev, Rostislav (2025): New insights into the taxonomy of Trechus Clairville, 1806 (Coleoptera: Carabidae) in the Balkans, with the first description of the male of Trechus bohemorum Pawlowski, 1973. Zootaxa 5661 (4): 538-552, DOI: 10.11646/zootaxa.5661.4.4, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
