Cionus olivieri Rosenschoeld, 1838

Jiang, Chunyan, Caldara, Roberto, Skuhrovec, Jiri & Zhang, Runzhi, 2020, Description and biological notes of the larva of Cionus olivieri Rosenschoeld, 1838 (Coleoptera, Curculionidae), with a comparison with other species of the tribe Cionini, ZooKeys 976, pp. 131-145 : 131

Cionus olivieri Rosenschoeld, 1838

Cionus olivieri Rosenschoeld, 1838: 725. Hoffmann 1958: 1222. Smreczyński 1976: 58. Košťál and Caldara 2019: 68.

Description of mature larva.

Figures 1 - 12 . Measurements (in mm). Body length: 9.00-9.75 (N = 18). Body width: 2.50-3.00 (N = 18, abdominal segment III-V). Head width (in front view): 0.68-0.74 (N = 10); length: 0.70-0.78 (N = 10).

General. Body subcylindrical, C-shaped, weakly curved, extremely soft, declivous and attenuate posteriorly (Figs 1 , 13 ).

Coloration. Head dark brown, very strongly sclerotized (Figs 1 , 13 ). All thoracic and abdominal segments yellow, pronotum partly pigmented and sclerotized (Figs 1 , 13 ).

Vestiture. Thoracic and abdominal segments with some minute and relatively long setae, cuticle minutely spiculate, pleural lobes distinct.

Head capsule (Figs 5 , 6 ). Head suboval and slightly rounded laterally, cranial suture undivided, wide, half-length of head. Frontal suture distinct, not extending to mandibular membrane. Endocarinal line present, reaching to half of frons. Anterior and posterior stemmata (st) present, projecting, anterior one located below stripe at side, externally close to antenna, posterior one located laterally. Setae on head piliform, varying in length, from very long to minute. Dorsal epicranium with three des; des1 and des4 reduced to a basal sensillum; des2 approximately as long as one-third length of des3; very long des3 located anteriorly on epicranium close to frontal suture; des5 located anterolaterally, as long as two-thirds length of des3. Frons only with one fs; fs1, fs2, fs3, and fs5 reduced to basal sensilla; long fs4 located near epistoma. Epicranium with only one les as long as des1. Ventral epicranium with two, minute ves. Posterior epicranium with four, minute pes1 - 4 and one sensillum. Postoccipital condyles distinct, hypopharyngeal bracon distinct. Tentorial bridge narrow, membranous in middle and half base of sides, strongly sclerotized at sides, with two pairs of acute auricular anterior projections.

Antenna (Fig. 7 ) located at the end of the frontal suture on each side, with one segment; sensory appendage (sensorium) three times as long as wide, circular in cross section, contiguous with frontal suture, with four conical sensillae.

Clypeus (Fig. 10 ) transverse-shaped, strongly sclerotized, with one sensillum and two cls of the same length, all in one line.

Mouthparts (Figs 9 - 12 ). Labrum (Fig. 10 ) transverse-shaped, strongly sclerotized, deeply concave in the middle at apex, with three lms, very short lms1 as long as lms3, and as long as half-length of short lms2, all localized centrally. Epipharynx (Fig. 11 ) with two small, stout, apically rounded ams; two relatively long, stout, apically rounded als; two epipharyngeal sensilla; mes and labral rods absent. Mandibles (Fig. 9 ) symmetrical, incisor section with two apical teeth and moderately rounded flange posterior to dorsal tooth, with many small teeth on inner side of anterior tooth, with one acute projection at base; molar section with two mds; mds2 moderately long, mds1 minute. Maxillae (Fig. 12 ) with maxillary palpi (mxp) two-segmented, basal segment with one tiny mxps, two clavate accessory appendages and one sensillum; distal segment sclerotized, with one sensillum, apex flattened with dense short irregular spiculate setae. Mala with four dorsal robust dms, gradually reducing in length; with three short, more acute vms. Stipes with one stps, two pfs, one mbs and one sensillum, very long stps located submedially on venter of base, mbs minute, long pfs1 three times longer than pfs2. Labium (Fig. 12 ) membranous excepting the premental sclerite; labial palpi with one segment, longer than wide, slightly globular at base, apex of palpi flattened with short, dense, irregular, spiculate setae, and one sensillum. Prelabium (prm) with sclerite distinctly dilated posteriorly and laterally, without posterior extension, cup-like, with one sensillum and one short prms; ligula with one tiny ligs. Postlabium (plb) with M-shaped sclerotization, with three plbs on sclerotized area, all setae separated from each other by about the same distance; short plbs1 and plbs3 as long as one-third length of plbs2.

Thorax (Fig. 2 ). Prothorax with pronotal shield partly sclerotized on dark brown smooth plate; with nine prns: two short ones on sclerotized area, two long and two short ones placed anteriorly, and three placed more medially; bicameral spiracle intersegmental between pro- and mesothorax, air-tube subequal to diameter of circular peritreme; pleural lobe with two ps; pedal area without setae; eusternum with one eus. Mesonotum with two folds, prodorsum without seta, postdorsum with two transversally aligned pds of the same length; epipleurum with one long eps; pleurum with one long ps; setae of pedal area and eusternum identical to that of prothorax. Chaetotaxy of metathorax identical to that of mesothorax.

Abdomen (Figs 2-4 ). Abdominal segments I-VII of almost equal lengths, remaining abdominal segments gradually decreasing in width posteriad. Tergites on abdominal segments I-VII with three folds, prodorsum wide and flat, mesodorsum narrow, with soft protuberance, postdorsum with soft protuberance; tergite on abdominal segment VIII with two folds, and on abdominal segment IX with no folds. Abdominal segment X reduced to four anal lobes of unequal size. Anus located subterminally. Spiracles (Fig. 8 ) bicameral, the eight abdominal spiracles located more ventrally up to ventral side of epipleurum, close to the anterior margin of abdominal segments I-VIII, size similar, each with two annulated air-tubes, pointing posteriad, air-tube subequal to diameter of circular peritreme. Abdominal segments I-VIII with three pds, located in one line, long pds1, two times longer than pds2, pds2 as long as pds3; with two ss, long ss1, short ss2, located in small indefinitely folds; with two eps, transversally aligned, long eps1, short eps2 as long as one-third length of eps1; with one long ps; and with one eus. Abdominal segment IX with one short ds, one slight long ps and one, minute sts. Abdominal segment X without setae.

Biological notes

The biology of this species was studied on Verbascum sinuatum in southern France by Hoffmann (1958), where it has two generations, in June and August. The ectophagous larva digs a deep groove on the underside surface of a leaf. When mature, it builds a cocoon, where pupation takes place, on the same plant. The adults of the second generation hibernate in the soil. The same behavior was reported in other species of Cionus feeding either on Verbascum ( Grandi 1929; Ruffo 1937; Hoffmann 1958) or Scrophularia ( Read 1977; Räther 1989).

We collected larvae of Cionus olivieri (Fig. 13 ) from Verbascum songaricum Schrenk in early July in mountain slopes at 1546 m altitude (Fig. 14 ) in Kyrgyzstan. This plant, widely distributed in the temperate zone of Eurasia including the Caucasus, central Asia, and Tacheng, Xinjiang, China, was never previously reported as host of Cionus . Two-thirds of the host plants had already produced seeds (Fig. 15 ), while the remaining parts were still blooming (Fig. 16 ). Larvae were eating on the flower buds, with head, thorax, and part of the abdomen burrowed into the ovary and leaving red excrement, with a layer of clear mucus on the surface of the body (Fig. 17 ). The feeding holes were regular circles (Fig. 18 ). The most serious damage by the larvae reached 90% of one branch (Fig. 19 ), and most of the damaged buds could not bloom. We also observed many adults, more than 50% of which were mating (Fig. 20 ) and most of them were in the middle part of the host plants.

Later, we collected larvae of Cionus olivieri (Fig. 21 ) from the same host plant species in mid-August in mountain slopes at 1577 m altitude (Fig. 22 ) in Kazakhstan. Damage of the larvae were similar to those in Kyrgyzstan. However, we did not find adults mating. Bearing in mind Hoffmann’s observations, we can assume that we probably collected the first generation in Kyrgyzstan and the second generation in Kazakhstan. However, in both situations, we did not find any cocoons on the plants (Fig. 15 ). This fact might be explained in two ways: both our observations were made before pupation or pupation happened in the soil. This second is unusual in Cionus but has been observed in Cionus alauda (Herbst, 1784) by Read (1977) and Cleopus pulchellus (Herbst, 1795) by Räther (1989).

Figures

Figure 5. Cionus olivieri, mature larva, head, frontal view (at antenna, st stemmata, cs cranial suture, ecl ecdysial line, fsu frontal suture. Setae: des dorsal epicranial, fs frontal epicranial, les lateral epicranial, pes posterio-epicranial). Scale bar: 0.5 mm.

Figure 12. Cionus olivieri mature larva, maxillolabial complex, ventral view (lbp labial palpus, pm postmentum, prm prementum. Setae: dms dorsal malar s., ligs ligular s., mbs basoventral s., mxps maxillary palps s., pfs palpiferal s., pms postmental s., prms premental s., stps stipital s., vms ventral malar s.). Scale bar 0.25 mm.

Figures 1 - 4. Cionus olivieri, mature larva: 1 habitus, lateral view 2 thoracic segments, abdominal segment I, and abdominal segments VIII-X, lateral view 3 pedal area, ventral view 4 anus (ThI-III, numbers of thoracic segments; AbdI-X, numbers of abdominal segment. Setae: ds dorsal s., eps epipleural s., eus eusternal s., pds postdorsal s., prns pronotal s., ps pleural s., ss spiracular s., sts sternal s.). Scale bars: 2 mm (1, 2), 1 mm (3, 4).

Figures 13 - 20. Biology of Cionus olivieri from Kyrgyzstan 13 larva on flower 14 habitat 15 seeds of host plant 16 flowering host plant 17 larva on feeding 18 feeding holes 19 damage on host plant by larva 20 copulating adults.

Figures 6 - 11. Cionus olivieri mature larva. 6 head, ventral view 7 antenna 8 spiracle 9 mandible 10 labrum and clypeus 11 epipharynx (hp hypopharyngeal bracon, fsu frontal suture, tb tentorial bridge). Seta (e): als anterolateral s., ams anteromedial s., cls clypeal s., lms labral s., les lateral epicranial s., mds mandible dorsal s., ves ventral epicranial s.). Scales bars: 0.5 mm (6), 0.25 mm (10, 11), 0.1 mm (8, 9), 0.025 mm (7).

Figures 21 - 22. Biology of Cionus olivieri from Kazakhstan. 21 larva on bud 22 habitat.