Pseudorchestes stobieckii ( Smreczyński, 1957 ), Zabaluev, 2025

Zabaluev, I. A., 2025, Taxonomy, biology and immature stages of the little-known weevil Pseudorchestes (Labiorchestes subgen. n.) stobieckii (Smreczyński, 1957) comb. n. (Coleoptera: Curculionidae: Rhamphini), Russian Entomological Journal 34 (1), pp. 82-92 : 83-87

Pseudorchestes stobieckii ( Smreczyński, 1957) , comb.n.

Figs 1–14 , 22– 25 .

Rhynchaenus (s.str.) stobieckii : Smreczyński, 1957: 130; Smreczyński, 1976: 71.

Rhynchaenus ? stobieckyi [sic!]: Korotyaev, 1999: 174.

Rhynchaenus? stobieckii : Korotyaev et al., 2007: 321.

Orchestes (s.str.) stobieckii : Benedikt et al., 2010: 201; Caldara, 2013: 147; Alonso-Zarazaga et al., 2023: 212.

MATERIAL (adults). Russia: Kursk Prov., Tsentralno- Chernozemny Nature Reserve, Dedov forest, 9. VI .1964 , K. Arnol'di — 1♀ ( ZMUM); ibid, Tolstyi log, northern slope, 19. VI .1964 , K. Arnol'di — 1♀ ( ZMUM); ibid, Streletskaya steppe, 3.VII.1966, K. Arnol'di — 1♀ ( ZMUM); Petropavlovka vill., mixed-grass steppe , 2. VI .1987 , D. Dovlar leg. — 1♀ ( ZMUM); Lipetsk Prov., Zadonsk Region , 2.5 km NE Lipovka vill., specially protected natural area “Lipovskaya Mountain”, 52.559037°N 38.890770°E, h= 144 m, 25. VI .2022 , Ya. Urbanus leg. — 1♂ ( IZCS); ibid, net-sweeping, 10–11. V .2024 , I. Zabaluev leg. — 1♂, 1♀ ( IZCS); ibid, 21–24. VI .2024 , I. Zabaluev leg., grown from mines on Nepeta nuda — 6♂♂, 1♀ ex. ( IZCS).

TAXONOMY. Since P. stobieckii ( Fig. 1 ) is similar to species of the genus Pseudorchestes (especially to P. angelovi ( Dieckmann, 1970)) in uniform pubescence of the body by grayish narrow parallel-sided scales, shallowly excised apically, the shape of the male aedeagus, the armature of the internal sac, the shape of spermatheca of female, the structure of hind legs, as well as the structure of the larvae and pupae, and like other Pseudorchestes is associated with open biotopes and develops on a herbaceous plant, we transfer this species and thus Pseudorchestes stobieckii ( Smreczyński, 1957) comb.n. However, the significant uniqueness of this species forces us to single it out into a separate subgenus. The differences in the main characters between the subgenera can be shown as follows:

1. Rostrum rather short, in male 2.43–2.55x as long as wide

( Fig. 2 ), in female 2.76–2.78x as long as wide ( Fig. 3 ). Antennae in both sexes inserted to the basal third of the rostrum. Scapus 1.3х as long as 1st segment of funicle ( Fig.

11). At the base of pronotum and elytra there are 3 long erect setae on each side. Profemora with one short thick spine ( Fig. 12 ), mesofemora with two long spines ( Fig.

13), metafemora with strong tooth-like projection and row of 9–10 spines of different sizes ( Fig. 14 ). Pro- and mesotibiae without uncus ( Fig. 12–13 ). Claws dentate. Body length 1.8–2.2 mm. On Lamiaceae ( Nepeta nuda ) ...........

.................................................. Labiorchestes subgen.n.

– Rostrum much longer, 3.5–7.0х as long as wide. Antennae inserted close to the base, at a distance that does not exceed the width of rostrum between them (expect for P. angelovi , see discussion). Scapus no longer than 1st segment of funicle ( Fig. 15 ) (expect for P. angelovi ). Sides of pronotum and elytra usually without long erect setae, rarely with them. Pro- and mesofemora without spines ( Figs 16–17 )

or with only one short spine. Pro- and mesotibiae with large hook-shaped uncus ( Figs 16–17 ). Claws dentate (in

P. astracanicus teeth minute, almost inconspicuous). On

Asteraceae and Chenopodiaceae ......................................

..................................................... Pseudorchestes (s.str.)

The morphological characters of P.stobieckii and its taxonomic position are considered in more detail in the discussion part.

ETYMOLOGY. The subgenus name is a combination of the classical name of family Lamiaceae — “Labiatae” and Orchestes .

DISTRIBUTION. Russia: Lipetsk Prov. (first record), Kursk Prov., Tambov Prov., Bashkortostan [ Korotyaev, 1999], Ingushetia [ Korotyaev et al., 2007]. Ukraine ( Ternopil Prov. [ Smreczyński, 1957], Lugansk Prov. [ Korotyaev, 1999]), Bulgaria [ Smreczyński, 1976], Slovakia [ Benedikt et al., 2010], Hungary, Turkey (Ispir Prov.) [ Korotyaev, 1999].

BIOLOGY. In general, the life cycle is similar to other Pseudorchestes . It can be found in open mixed-grass biotopes, edges of oak forests ( Fig. 22 ), steppe gullies and steppe slopes from the beginning of May to the beginning of July. Monophagous on Nepeta nuda ( Lamiaceae ) ( Fig. 23 ). Eggs are laid in the midrib, the larva makes a corridor, filled with frass, towards the apex of the leaf, which then expands into a large bubble-shaped mine, which in the end occupies most of the leaf blade. All mines were found in the upper half of the plant, often on small upper leaves. The larva pupates in a cocoon inside the mine, which at this point becomes noticeably darker and begins to dry out ( Figs 24–25 ). The pupal phase is very short and, according to our observations, takes no more than a week. A new generation appears in the second half of June, and the greatest number of finds were made in this time.

The larvae and pupae are parasitized by Pnigalio cristatus (Ratzeburg, 1848) , P. incompletus (Bouček, 1971) and Neochrysocharis formosus (Westwood, 1833) ( Hymenoptera : Eulophidae ) (determined by O.V. Kosheleva). In addition, some of the larvae were found dead apparently from fungal diseases.

It is interesting to note that mines of the leaf beetle Dibolia carpathica Weise, 1893 ( Chrysomelidae : Galerucinae : Alticini) were found on the same plants as the mines of P. stobieckii . They are similar to weevil mines, but are located mainly not on the upper leaves, but on the large lower leaves, in the form of an opaque flat spot that occupies 1/4–1/3 of the apical part of the leaf blade. The larva Dibolia leaves the mine to pupate and pupates in the soil, adults emerge after about 10 days.

Description of mature larva

Figs 26–35 .

MATERIAL. Lipetsk Prov., Zadonsk Region , 2.5 km NE Lipovka vill., specially protected natural area “Lipovskaya Mountain”, 52.559037°N 38.890770°E, h= 144 m, 21–23. VI.2024, I.A. Zabaluev leg. — 5 specimens extracted from leaf mines on Nepeta nuda .

MEASUREMENTS (in mm). Body length: 3.02–3.34 (mean 3.15). Prothorax width: 0.56–0.60 (mean 0.58). Mesothorax width: 0.76–0.78 (mean 0.76). Metathorax width: 0.76–0.80 (mean 0.78). Abdominal segments I width: 0.82– 0.96 (mean 0.89). Head width: 0.34–0.38 (mean 0.36). Head length: 0.27–0.29 (mean 0.28).

GENERAL HABITUS. Body ( Fig. 26 ) almost straight, elongated, greenish-white. Head ( Fig. 27 ) brown, endocarina and posterior margin of epicranium dark brown. Prothorax dorsally with two sclerotized brown shields separated above by a narrow stripe, ventrally with three separate sclerotized shields. Thoracic segments conically narrowed forward, prothorax small, narrowed, pedal lobes not protruding.Abdominal segments I–VII on the dorsal side along the middle with transverse protruding cuticular callus-like fold. Segments VIII–IX without such fold and gradually conically narrowed towards the apex. Epipleural lobe on abdominal segments I–VIII strongly convex and protrude noticeably laterally. Spiracles bicameral, not colored, placed on prothorax and on abdominal segments I–VIII. Anus located terminally.

CHAETOTAXY OF BODY. Setae yellowish, very fine, hair-like, and of varying length. Pronotum ( Fig. 28 ) with nine prns unequal length: prns 1 medium, prns 2 very short, prns 3–4 and prns 9 short, prns 5–8 long. Meso- and metanotum with very short pds 1, long pds 2–3, and very short as. Pleural parts of prothorax with two very long ps; pleural parts of meso- and metathorax with very short ss, very long eps and ps approximately equal length. Pedal lobe with three pda medium length. Ventral parts with one long and one medium eus. Abdominal segments I–VIII ( Fig. 28 ) with short prs, two long and one short pds, minute and long ss, short and very long eps, very short and long ps and two medium eus. Abdominal segment IX ( Fig. 29 ) with one very short and two long ds, short and long ps and two long sts. Abdominal segment X with three very short and robust ts. In addition, along the anterior margin of meso- and metathorax there are four greatly reduced minute setae (one each next to pds 1, ss, pda, and eus), which are visible at 400x magnification; abdominal segments I–VIII bear three similar setae (next to prs, ss, and eus); abdominal segment IX with one setae (on ventral part).

HEAD CAPSULE. Head ( Fig. 30 ) 1.3–1.4x as wide as long, almost one-third retracted into prothorax, the posterior margin deeply and broadly emarginated, and strongly thickened. Frontal sutures distinct. Endocarinal line very thick, heavily sclerotized, protrudes beyond the posterior edge of epicranium. Hypopharyngeal bracon absent. Frontal area with minute fs 2, short fs 4, long fs 5, and with two sensory pores — between fs 2 and fs 4, and proximal to fs 2. Dorsal area with minute des 1–3 and long des 5, and with two sensory pores — between des 2 and des 5, and next to des 1. Posterior epicranial area with five minute pes. Lateral area with very short les 1 and long les 2. Ventral area ( Fig. 31 ) with two minute vcs.

CLYPEUS AND MOUTHPARTS. Clypeus ( Fig. 32 ) transverse, approximately 2x as wide as long, emarginate at the anterior margin, about the middle with two very short cls and with one clss between them. Labrum ( Fig. 32 ) trapeziform, approximately 1.9x as wide as long, with short lrs. Epipharynx ( Fig. 33 ) with three als, equal in length, three shorter and thinner ams and two elongated finger-like mes; also with large sensory pore located anteromedially. Labral rods ( lr) short-oval, approximately 1.3x as long as wide, not converging posteriorly. Mandibles ( Fig. 34 ) rather robust, triangular, with two apical teeth and several small denticles, with two very short mds equal in length and one sensory pore. Maxilla ( Fig. 35 ) with long stps, long pfs 1, short pfs 2, very short mbs and two sensory pores (one near the base of pfs 1, other distal to stps). Mala on dorsal side with six finger-like dms, and on ventral side with four very short thin vms. Maxillary palpi consist of two palpomeres, basal palpomere with one short mxps. Prelabium with one prms and two small sensory pores. Ligula with three minute ligs. Labial palpi consist one palpomere. Postlabium elongated, with three pms: pms 2 very long, pms 1 short, approximately 0.5х as long as pms 2, pms 2 even shorter, approximately 0.3х as long as pms

2

.

VARIABILITY. Despite the relatively small number of larvae studied, they all differed quite significantly in the position of some setae and sensory pores, especially on the head capsule. For example, pes can be arranged in single row or in two clusters, moreover des 1 being able to shift and become part of pes cluster. The position of the setae can vary even in one larva on different sides of the head capsule. However, no differences in the length of the setae or their total number have been identified.

COMPARATIVE NOTES. In general habitus, the described larva is very similar to the larvae of Pseudorchestes . It differs from the larva of P. circumvistulanus (Białooki, 1997) in its yellowish-brown head and uncolored spiracles, from the larvae of P. pratensis (Germar, 1821) and P. abdurakhmanovi (Korotyaev, 1991) in it’s the ventral sclerotized shield on the prothorax divided into three separate parts, and from the first species, in addition, in its brown head. Chaetotaxy and the structure of the mouth parts are described in detail only for P. abdurakhmanovi [ Zabaluev, 2023], the larva of P. stobieckii differs in its short-oval labral rods, longer pms and prms, five pes, equal-length cls and other very small differences. The larvae of the other species of Pseudorchestes are not known, but it can be expected that they will also be extremely similar to each other.

Description of pupa

Figs 36–37 .

MATERIAL (pupae). 6 specimens collected together with larvae.

MEASUREMENTS (in mm). Body length: 1.96–2.20 (mean 2.16). Body width: 0.78–0.87 (mean 0.80). Head width: 0.35–0.37 (mean 0.36).

GENERAL HABITUS. Body elongated, greenish-white or yellowish-white, setae light brown, eyes reddish brown. Some specimens have small light spots on the sides of abdominal tergites. Rostrum quite short, 2.17–2.82x as long as wide, reaching mesocoxae. Antennae attached directly at the base of rostrum. Pronotum trapeziform, 1.45– 1.63x wider than long. Spiracles placed dorso-laterally on abdominal segments I–VI. Urogomphi short, paired, converging, weakly sclerotized, bear stout acute spine at the apex. Surface of cuticle especially on pronotum, abdominal tergites, legs, sides of rostrum, etc. covered with distinct rough scabrous microsculpture consisting of small denticulate asperites.

CHAETOTAXY. Setae thin, light-brown, from very long to minute, located at the apices of small rounded tubercles, the size of which is proportional to the size of setae. Head with one relatively short os and two very long and rather robust vs, almost equal in length. Rostrum without any setae. Pronotum with 8 setae on each side: one as, two ds, one sls, two ls, and two pls. As the longest setae on the body, located at the very anterior margine of pronotum, followed by very long ds 1 and sls; in the posterior part of pronotum there is row of three setae ds 2, pls 1 and pls 2, of which pls 1 long, and ds 2 and pls 2 slightly shorter. Lateral sides of pronotum with pair of relatively thinner and shorter ls. Mesonotum with two short d, both placed on one convex tubercule. Metanotum with two d such as those on mesonotum, but placed on separate convex tubercles. Dorsal parts of each abdominal segments I–VIII with one d, the length of which gradually increases to segment VIII. Pleural parts of each abdominal segments I–VIII with two ps: ps 2 long, ps 1 minute (visible at 800x magnification); ps on segment VIII strongly displaced to the ventral side. Ventral part of abdominal segment IX with two short and stout v. Urogomphi without setae. Apex of femora with two fes: fes

1

short, fes

2

very long.

COMPARATIVE NOTES. Described pupa is very similar to the pupae of Pseudorchestes abdurakhmanovi , P. circumvistulanus and P. pratensis , especially in chaetotaxy of meso- and metathorax, abdomen and legs, as well as in the shape of urogomphs, but differs in shorter and thicker rostrum without rs and pas, wider pronotum with two ls instead of one, and an additional pair of ds at the posterior part.

Figures

Figs 1–3. Pseudorchestes stobieckii, habitus of adult and lateral view of rostrum. 1 — habitus (Lipetsk Region); 2 — rostrum of male; 3 — rostrum of female. Рис. 1–3. Pseudorchestes stobieckii, обЩий вид имаго и головотрубка, вид сбоку. 1 — обЩий вид (ЛипецкаЯ обл.); 2 — головотрубка самца; 3 — головотрубка самки.

Figs 4–10. Pseudorchestes stobieckii, details of structure. 4 — aedeagus, dorsal view; 5 — ibid, lateral view; 6 — spiculum gastrale; 7 — spermatheca; 8 — spiculum ventrale; 9 — 7th tergite of male; 10 — metendostenite. Рис. 4–10. Pseudorchestes stobieckii, детали строениЯ. 4 — Эдеагус, вид сверху; 5 — тоЖе, вид сбоку; 6 — spiculum gastrale; 7 — сперматека; 8 — spiculum ventrale; 9 — 7-й тергит самца; 10 — Эндостернит Заднегруди.

Figs 11–21. Rhamphini, antennae and legs: 11–14 — Pseudorchestes stobieckii; 15–18 — P. smreczynskii; 19–21 — Rhynchaenus xylostei; 11, 15 — antennae; 12, 16, 19 — fore legs; 13, 17, 20 — middle legs; 14, 18, 21 — hind legs. On photos 12, 16, and 20 coxa and trochanter removed. Black arrows mark the position of uncus. Figs 11–21. Rhamphini, усики и ноги: 11–14 — Pseudorchestes stobieckii; 15–18 — P. smreczynskii; 19–21 — Rhynchaenus xylostei; 11, 15 — усики; 12, 16, 19 — передние ноги; 13, 17, 20 — средние ноги; 14, 18, 21 — Задние ноги. На фото 12, 16 и 20 таЗик и вертлуг удалены. Чёрные стрелки укаЗывают на полоЖение ункуса.

Figs 22–25. Habitats and biology of Pseudorchestes stobieckii: 22 — specially protected natural area “Lipovskaya Mountain” (Lipetsk Prov.); 23 — Nepeta nuda, host plant; 24–25 — dried mines on the leaves of N. nuda. Рис. 22–25. Местообитание и биологиЯ Pseudorchestes stobieckii: 22 — особо охранЯемаЯ природнаЯ территориЯ «ЛиповскаЯ гора» (ЛипецкаЯ обл.); 23 — Nepeta nuda, кормовое растение; 24–25 — усохшие мины на листьЯх N. nuda.

Figs 26–29. Pseudorchestes stobieckii, larva habitus and chaetotaxy: 26 — lateral view; 27 — head and prothorax, front view; 28 — chaetotaxy of thorax (Th1 — prothorax, Th2 — mesothorax, Th3 — metathorax) and 1st abdominal segment (Ab1); 29 — chaetotaxy of the 9th (Ab9) and 10th (Ab10) abdominal segments. Рис. 26–29. Pseudorchestes stobieckii, обЩий вид личинки и хетотаксиЯ: 26 — вид сбоку; 27 — голова и переднегрудь, вид спереди; 28 — хетотаксиЯ груди (Th1 — переднегрудь, Th2 — среднегрудь, Th3 — Заднегрудь) и 1-го сегмента брюшка (Ab1); 29 — хетотаксиЯ 9-го (Ab9) и 10-го (Ab10) сегментов брюшка.

Figs 30–35. Pseudorchestes stobieckii, details of the larvae structure: 30 — head capsule, dorsal view; 31 — left half of the head capsule, ventral view; 32 — clypeus and labrum; 33 — epipharynx; 34 — mandible; 35 — maxillolabial complex (left maxilla in ventral aspect, right maxilla in dorsal aspect). Рис. 30–35. Pseudorchestes stobieckii, детали строениЯ личинки: 30 — головнаЯ капсула с дорсальной стороны; 31 — леваЯ половина головной капсулы с вентральной стороны; 32 — наличник и верхнЯЯ губа; 33 — Эпифаринкс; 34 — мандибула; 35 — максиллолабиальный комплекс (леваЯ максилла покаЗана с вентральной, а праваЯ — с дорсальной стороны).

Figs 36–37. Pseudorchestes stobieckii, pupa habitus and chaetotaxy: 36 — ventral view; 37 — dorsal view. Рис. 36–37. Pseudorchestes stobieckii, обЩий вид куколки и хетотаксиЯ: 36 — вид сниЗу; 37 — вид сверху.