Material Examined

POLAND: Biebrza National Park, Brzostowo, UTM: EE90, Pupae 1♂ 1♀ and several teneral adults (30 July 1999), and two mature larvae (8 June 2000) collected from the internodes of canarygrass reed (P. arundinacea L.) growing on old river bank, leg. MW (MNHW).

General Morphology

All thoracic and abdominal segments white-yellow. Cuticle smooth. Pronotal area of first thoracic segment feebly sclerotized, light yellow. Body slender, elongate, slightly curved (Fig. 6), and rounded in cross section, at widest place (AbI) measuring up to 1.40 mm; total body length: 7.5–7.8 mm. Prothorax slightly smaller than similar to each other meso-and metathorax. AbI–III of almost equal length, slightly bigger than metathorax. AbIV shorter than AbV–VI, AbVII–VIII decreasing gradually to the terminal parts of the body, AbIX again distinctly smaller than previous ones, and AbX reduced to three anal lobes of unequal size. Dorsal parts of AbI–VII divided into three lobes, AbVIII with two dorsal lobes. Lateral folds of AbI–IX well isolated, on segments VII–IX developed into conical protuberances. Spiracles nine pairs, bicameral, first pair placed on anterior margin of pronotum, next seven pairs lateromedial, and the last pair placed dorsolaterally on AbVIII.

Chaetotaxy

Feebly developed, setae light yellow, hairform, varying in size, and poorly distinguished. Prothorax on each side (Fig. 7) with seven prns of unequal length (four long and three short, all located on sclerotized shield), one vpls and one short msts. Meso- and metathorax both on each side with one pds, one dpls, one vpls, and one msts. Each pedal area of thoracic segments with one long and three short pda. AbI–VIII with paired one short pds, one short dpls, one vpls, and two short msts. (Fig. 8). AbIX with paired one ds, one ls, and one sts (Figs. 9–11).

Head and Mouth Parts

Head light yellow; width: 0.84–0.86 mm, length: 0.80–0.82 mm, oval shaped, slightly oblate bilaterally, frontal-suture distinct, and Y-shaped. Setae on head hairform, different in length. Des₁ three times longer than des ₃, both located in central part of epicranium, des₂ as long as des₁, placed on frontal suture, des₄ as long as des₁ located anterolaterally (Figs. 12 and 13). Fs₂ as long as des₁, placed laterally, close to epistome. Les₁ as long as des₃ and les₂ slightly shorter than des₁. Postepicranial area with one very short pes (Fig. 13). Frons with three pairs of pores placed medially; one pore placed laterally on each side of head, one pare near to des₁, one near to des₄. and last one close to les₂. Antenna located on end of frontal suture; antennal segment with sensorium conical, slightly elongated, and located medially; basal membranous article with one elongated sensilium (Fig. 14).

Labrum (lrm) (Fig. 15) ∼2.7 times as wide as long, with three pairs of lrms_1–3 of different length; lrms₂ almost twice as long as lrms₁ and lrms₃, all lrms placed on distinct protuberances; anterior margin slightly roundly emarginate. Clypeus (cl) (Fig. 15) 3.6 times as wide as long, with three triangular and equally long cls_1–3 based on protuberances, localized post-eromedially; anterior margin of clypeus gently arcuated inwards. Epipharynx (Fig. 16) with three pairs of finger-like als_1–3 of different length; two pairs of short ams_1–2; and two pairs of conical mes_1–2. Labral rods (lr) kidney shaped, slightly converging posteriorly. Mandibles (Fig. 17) slightly truncate, bifid, teeth of unequal length, and the cutting edge almost straight. Mds short, hairform. Maxillary stipes (stp) (Fig. 18) with one stps and two short, equally long pfs; mala (ma) with six bacilliform or finger-like dms_1–6 of different length; vms_1–3 short, of almost equal length; vms shorter than dms. Maxillary palps (mpa) with two segments; each of them with a pore, basal palpomere 1.3 times longer than distal one. Apical part of distal palpomere with a group of 5–6 long, conical, and cuticular processes. Praelabium (plb) (Fig. 19) rounded, with three pairs of variously long plbs_1–3 (plbs₁ located posteriorly on premental sclerite, plbs_2–3 near to each of palpomera). Ligula with four pairs of hairform, micro ligs_1–4 of equal length. Premental sclerite well visible, in a form of complete ring, with elongated proximal part. Labial palps (lpa) one-segmented, located on conical protuberances; each palp with some short, cuticular apical processes, and a pore. Postlabium (pslb) (Fig. 19) densely covered with small, triangular cuticular processes, and with three pairs of short, almost equal pslbs_1–3, the first pair localized medially, remaining two pairs laterally.

General Morphology

Body length: 9.0 mm (♀), 8.0 mm (♂), maximum width at the level of mesocoxae: 4.8 mm (♀), 3.8 mm (♂), head width: 0.88 mm (♀), 0.84 (♂). Body elongated, slender, white, or yellowish. Cuticle smooth. Rostrum long, ∼5.5 times as long as wide, surpassing mesocoxae in repose range. Antennae moderately long and slender. Pronotum almost as wide as long. AbI–IV of almost equal length, segments V–VIII gradually diminished, VIII semicircular, and IX distinctly smaller than preceding ones. Pseudocerci very short and triangular. Sexual dimorphism visible in the structure of AbIX: gonotheca of ♀ divided and ♂ undivided. Five pairs of functional spiracles placed laterally on AbI–V.

Chaetotaxy

Setae short, straight, of unequal length, light brown or brown, on rostrum, head, and pronotum based on small protuberances. Rostrum with a pair of rs; head capsule bearing paired vs, sos, pas, and two pairs of os_1–2 (Fig. 21). Setae rs, vs, and sos₁ darker and two times longer than remaining ones. Pronotum on each side with paired as_1–2, ls_1–2, ds_1–2, and pls_1–2 (Fig. 23). Chaetotaxy of metathorax as on mesothorax, consisting of paired triplets d_1–3 (Fig. 22). Each femoral apex with a pair of fes of almost equal length (Fig. 20). Tergal parts of AbI–VIII each with two triplets of d_1–3 located laterally, respective sternal parts of AbI–VIII with a short seta (l₁) close to the border with tergum. AbIX with paired ventral (v₁) and dorsal setae (d₁) (Figs. 22, 24).

Ecology

The Lower Biebrza Valley is the only area in Poland where B. elegans, extremely rare and endangered European weevil, was found in the past 70 years (Wanat 2004, 2005). The population there is associated exclusively with the canarygrass reed (P. arundinacea L.), which is exceptional in this species. It inhabits old-rivers and channels near their mouth to the Biebrza river, connected with the main river bed, and thus with a partly refreshed water till at least June after the spring melt. Larval development takes place in the submerged stolons of the grass and is always restricted to the most basal second or third internode. The larvae feed and pupate inside the stem, always one per internode, and fresh beetles were found there since end of July, when the inhabited basal internodes are often emerged after the summer fall down of water level. However, phenology of this species is highly dependent on the seasonally variable water level in the river and its drainage, and its reproductive success is apparently largely limited in years with dry springs. It is likely that in extremely dry years and low water supply in winter/spring a part of the specimens do not attempt to breed and remain in diapause until the next season, as it was confirmed for the closely related B. majzlani (Kodada et al. 1992). Adults of B. elegans are poorly active, flightless, and nonswimming beetles, and they rarely appear on emerged parts of stems during a day, spending long time under water, and breathing thanks to the plastron or the oxygen produced by plants. They are surprisingly resistant to standard procedures of killing in preservation liquids or ethyl acetate mist, and it takes an unusually long time to get them quiet compared with all other beetles we ever experienced.

The biology of B. elegans in the Biebrza Valley is very similar to that studied in B. frivaldszkyi (Gosik 2006b). The latter species is common and abundant throughout the Southern Biebrza Basin, including all places occupied by B. elegans (Wanat 2005). Although both these weevils develop in the stems of P. arundinacea, the larvae of B. frivaldszkyi have never been found beside those of B. elegans in basal internodes of the grass. They apparently develop in more distant internodes closer to water surface, thus the larvae of these two weevil species do not meet on the same plant.

The host plant of the Biebrza population of B. elegans is not that well known for this weevil in Europe, i.e., the common reed Phragmites australis (Cav.) Trin. ex Steud. (Brauns 1891, Poot 1972, Dieckmann 1983, Messner and Dieckmann 1987, Balalaikins and Bukejs 2010). Moreover, Kodada et al. (1992) indicated and illustrated slight morphological differences between various populations of B. elegans in Western Palaearctic. Therefore, taxonomic status of the Biebrza population of B. elegans remains still not well established, despite lack of convincing morphological differences of adult beetles from those reared from Ph. australis in Germany (Mark Brandenburg: Templin).

Material Examined

POLAND: Wieprzecka Góra near Zamość, UTM: FB51, 21 June 1994, nine larvae of different instars, leg. J. Szypuła & MW (MNHW, RG). All collected from top parts of rachitic golden chamomile (A. tinctona L.) growing mostly on the border between natural xerothermophilous swards (Thalictro-Salvietum type communities) and agrocoenose (wheat field).

General Morphology

All thoracic and abdominal segments yellow. Cuticle minutely spiculated. Pronotal area of first thoracic segment sclerotized, light brown. Body (L₃) 1.8–3.2 mm long, slender, curved, and rounded in cross section (Fig. 25). The thickest place of body (AbI) up to 0.75 mm of height. Prothorax narrow, smaller than mesothorax. Metathorax similar to mesothorax, both slightly smaller than AbI. AbI–V almost of equal length, subsequent segments gradually decreasing, AbIX semicircular in dorsal view. AbX reduced to four anal lobes of equal size. Dorsal parts of AbI–VIII divided into three lobes. Lateral lobes on abdominal segments well isolated, on AbVII–VIII each forming a small protuberance on the posterior segmental margin. Spiracles in all nine pairs, bicameral, first pair placed in anterior margin of pronotum, next seven pairs lateromedial, and the last one placed dorsolaterally on Ab VIII.

Chaetotaxy

Setae minute, light yellow, hairform, differing in size, and poorly distinguishable. Each side of prothorax (Fig. 26) with six prns unequally long (three long and one short located on the sclerotized part, two short placed close to the spiracle), one vpls and one short msts. Both meso- and metathorax on sides with three pds of different length, one dpls and one msts. Pedal areas of thoracic segments each with one long and five short pda. AbI–VIII on each side with one short prs, one medium long pds, two dpls of different length, and 2 short msts (Fig. 27). AbIX with paired relatively long ds, ls, and sts (Figs. 28–30).

Head and Mouth Parts

Head (L₃) brown or light brown; width: 0.30–0.36 mm, length: 0.27–0.32 mm, oval shaped, frontal suture distinct, and Y-shaped. Setae, on head hairform, are of different length. Setae des₁ and des₃ moderately long, located in central part of epicranium; des₂ very long, placed on frontal suture; des₄ as long as des₂, located anterolaterally, and close to the stemma (Figs. 31 and 32). Setae fs₂ as long as des₂, placed laterally close to epistome. Setae les₁ short, les₂ slightly shorter than des₂. Postepicranial area with a pair of very short pes. Frons with five pairs of pores distributed along frontal suture; four pores placed laterally on each side of head, one pore near des₁, and the last one close to des₂. Antenna located on end of frontal suture; antennal segment with sensorium conical, slightly elongated, and located centrally; basal membranous article with seven sensillae of different shape and size (Fig. 33).

Labrum (Fig. 34) approximately two times as wide as long, with three pairs of Inns of different length; lrms₂ almost two times longer than lrms₁ and lrms₃, all lrms placed on protuberances. Clypeus three times as wide as long, with paired equally long short-conical cls_1–2 localized posteromedially; anterior margin almost straight. Epipharynx (Fig. 35) with three pairs of blunt, finger-like als of different length; 2 pairs of short, triangular ams, and 2 pairs of finger-like mes; labral rods elongated, converging posteriorly. Mandibles (Fig. 36) slightly truncate, bifid with teeth of unequal length, and the cutting edge with a small triangular tooth. Mds short, hair-like. Maxilla (Fig. 37) having stipes with one stps and two pfs, (pfs₁ longer than pfs₂); mala with seven bacilliform or spatulate dms of different length; three vms short, almost equal in length; vms shorter than dms; maxillary palps with two palpomeres, distal one 2.4 times longer than basal one, with a single pore sub basally and a group of 5–6 distinct, conical cuticular processes apically. Praelabium (Fig. 38) almost rounded, with two pairs of unequally long plbs (plbs₁ located posterolaterally, plbs₂ laterally on the premental sclerite). Ligula with four pairs of hairform micro ligs of equal length. Premental sclerite well visible, forming incomplete ring. Labial palps one-segmented, located on conical protuberances; each palpomere with several short, apical cuticular processes, and a pore. Postlabium (Fig. 38) with three pairs of variously long pslbs; pslbs₂ distinctly longer than the other ones and directed outward, the first pair localized medially, the remaining one laterally.

Ecology

The host species discovered at Wieprzecka Góra hill in Poland by J. Szypuła is A. tinctona, and dwarf plant specimens, growing in suboptimal conditions, and usually on bare ground, were evidently preferred for oviposition there. The larvae are in fact exophagous, although they were found hidden deeply in tight apical leaf buds of golden chamomile, so at least by sunny day they are not exposed on the plant. No traces of pupal chambers were observed in the plants occupied by mature larvae and, considering external larval feeding, pupation is almost certainly in the soil near the host plant, like it was confirmed for the close relative B. lutulosus.

Three localities of this little known and very rare species in Poland, though all open and sunny, are very different regarding environmental conditions. Its locus typicus in Opoka Wielka and the rich site on Wieprzecka Góra (well over 100 adults collected in all) are warm and floristically rich steppe grasslands growing on calcareous soils, while the last discovered site in Piątnica (Wanat 2005) is an initial ruderal plant community covering sandy and clay ground of abandoned gravel-pit.

Interestingly, the intensely yellow coloration of larval body is contrasting with the plant substrate, which is silver-white due to dense clothing of hairs on early developing leaves. However, it fits well the deeply yellow color of golden chamomile flowers, being still in buds with a small yellow “eye” when the larvae end their development. Thus it may be considered a mimics, especially for mature larvae being too large to hide inside the leaf bud. On the contrary, the adults are concolorous with a young leaf surface due to white hydrofuge coating of the body, but they are also practically invisible on the ground near the plant.

Material Examined

POLAND: Biebrza National Park, Szostaki, UTM: EE90, 16 June 2010, four larvae of different instars collected from florets of toad rush (J. bufonius L.) (further six larvae taken with plants to laboratory and reared to adults on 7 July 2010); leg. MW (MNHW, RG).

General Morphology

All thoracic and abdominal segments grayish, covered (especially on dorsal parts) by different in size spots, created by hardened, dark-pigmented cuticle. Pronotal area of first thoracic segment well sclerotized, black. Body (L₃) 3.4–3.7 mm long, slender, elongated, visibly curved, and slightly oblate dorsoventrally (Fig. 39); the thickest place (first abdominal segment) measuring up to 0.80 mm in height. Prothorax narrow, meso- and metathorax similar to each other and almost equal in size with the first segment of abdomen. AbI–V of almost equal length, subsequent ones gradually decreasing, AbIX almost semicircular in dorsal view. AbX reduced to three anal lobes of equal size. Dorsal parts of AbI–VII divided into three lobes, on AbVIII into two lobes. Lateral lobes on abdominal segments well isolated, on segments VIII and IX forming a small protuberances on posterior margin of each ones. Spiracles nine pairs, bicameral, first pair placed on anterior margin of pronotum, next seven pairs lateromedial, and last pair placed dorsolaterally on Ab VIII.

Chaetotaxy

Feebly developed, setae light brown, hairform, variably sized, and poorly visible. Prothorax (Fig. 40) on each side with four long, equally sized prns placed on a sclerotized part, one vpls and one short msts. Sides of meso- and metathoracic segments each with three short, equally long pds, one vpls, and one msts. Pedal area of each thoracic segment with one long pda. Each side of AbI–VIII with three short pds, one short dpls, 1 vpls, and two short msts (Fig. 41). AbIX with paired ds, ls, and sts (Figs. 42–44).

Head and Mouth Parts

Head black; width (L₃): 0.36–0.38 mm, length: 0.32–0.30 mm; slightly oblate bilaterally, frontal suture distinct, and Y-shaped. Setae of the head hairform, different in length (Figs. 45 and 46). Des₁ three times longer than des₃, both located in the central part of epicranium, des₂ as long as des₁, placed on frontal suture, des₄ as long as des₁ located near to stemmata. A single micro-seta (des₅) present close to des₄ (Figs. 45 and 46). Seta fs₂ as long as des₁, placed anterolaterally. Seta les₁ as long as des₃, les₂ almost as long as des₁. Postepicranial area with group of four short pes_1–4. Frons with five pairs of pores distributed more or less along frontal sutures; further pairs of pores placed outside frontal area, one pair near des₁, other near des₄ and two pairs close to head margin (Fig. 46). Antenna located at end of frontal suture; antennal segment with sensorium conical, elongated, and located medially; basal membranous article with five sensillae of different shape and length (Fig. 47).

Labrum (Fig. 48) approximately three times as wide as long, with three pairs of lrms_1–3 of different length; lrms₂ very long, lrms₁ shorter than other ones; all lrms placed on protuberances; and anterior margin of labrum slightly bisinuate. Clypeus (Fig. 48) 3.5 times as wide as long with three triangular, short cls_1–3, of equal length, localized posteromedially; and anterior margin of clypeus broadly emarginate. Epipharynx (Fig. 49) with three pairs of blunt, finger-like als_1–3 of almost equal length; three pairs of short, triangular ams_1–3, and two pairs of conical mes. Labral rods wedge-shaped with bisinuate inner margins, almost parallel. Mandibles (Fig. 50) truncate, bifid, teeth of slightly unequal length, and the cutting edge with a blunt prominence; mds_1–2 short, hairform. Maxillary stipes with 1 stps and 2 pfs of equal length; mala with seven finger-like dms_1–7 of different length; vms_1–3 of almost equal length; and vms shorter than dms (Fig. 51). Maxillary palps with two palpomeres; basal palpomere 2.5 times longer than distal one, the latter apically with a group of five conical, cuticular processes. Praelabium (Fig. 52) heart shaped, with three pairs of variously long plbs_1–3 (plbs₁ located posteromedially, plbs_2–3 placed on premental sclerite). Ligula with three pairs of hairform, micro ligs_1–3 of equal length. Premental sclerite well visible, forming incomplete ring. Labial palps one-segmented, each palpomere with some short, cuticular apical processes and a pore. Postlabium (Fig. 52) with three pairs of pslbs_1–3, the first pair situated medially, the remaining two pairs laterally; pslbs₂ longer than two other ones.

Ecology

The host plant of this species is Juncus bufonius L. Late larval instars are permanently exophagous and feed partly or fully exposed on the sepals and petals (Figs. 4 and 5), occasionally also on the leaves wrapped around the bract supporting the floret. Pupation takes place in the permeable, sandy soil near the host plant. Pupal stage takes no longer than a week (Wanat 2011).