Research Article |
Corresponding author: Runzhi Zhang ( zhangrz@ioz.ac.cn ) Academic editor: Miguel Alonso-Zarazaga
© 2020 Chunyan Jiang, Roberto Caldara, Jiri Skuhrovec, Runzhi Zhang.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Jiang C, Caldara R, Skuhrovec J, Zhang R (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: 131-145. https://doi.org/10.3897/zookeys.976.53930
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The mature larva of Cionus olivieri Rosenschoeld, 1838 is described and illustrated in detail for the first time. It is compared with those known from the same genus and other genera in the tribe Cionini and with those of the hypothesized sister tribe Mecinini in the Curculioninae. The larvae of Cionus have three distinctive diagnostic features: the reduced number of setae on the epicranium (only two or three des and one or two fs) and on the epipharyngeal lining (only two als, two ams, and no mes); i.e., distinctly fewer than the most frequent number of setae in weevils, and mandibles dentate or angulate internally near the base. If considered together with Stereonychus Suffrian, 1854, the other genus of Cionini with larvae studied in detail, it is preliminarily suggested that mature larvae of this tribe might be characterized by six main diagnostic features: (1) labial palpi one-segmented, (2) labral rods absent, (3) pedal areas swollen to form large lobes or prolegs, (4) mandible with sharp apical teeth, (5) reduced number of fs on frons, only one or two fs, and (6) reduced number of epipharyngeal setae (two or three als and two or three ams, but no mes). It was noticed that C. helleri Reitter, 1904 from Japan, a very distinct species in the genus for some characters of the adult, also possesses distinctive characters in the larva which are uncommon among known cionines. New biological data on C. olivieri with the discovery of its host plant, Verbascum songaricum (Scrophulariaceae), in central Asia are also reported.
biology, Curculioninae, ecology, immature stages, Verbascum songaricum, weevils
The tribe Cionini Schoenherr, 1825 in the subfamily Curculioninae Latreille, 1802 (Curculionidae) currently comprises seven genera occurring predominantly in the Palearctic region (Alonso-Zarazaga et al. 1999). The largest genus is Cionus Clairville, 1798, which is also represented in the Afrotropical and Oriental regions, whereas the other genera include fewer than ten species (Cleopus Dejean, 1821; Nanomicrophyes Pic, 1908; Stereonychus Suffrian, 1854) or are monotypic (Cionellus Reitter, 1904; Patialus Pajni, Kumar & Rose, 1991; Stereonychidius Morimoto, 1962). Based on the Palearctic species,
Adults of Cionus olivieri Rosenschoeld, 1838 are clearly distinguished from other species of Cionus by the following features taken together: body size on average large (♂♂ 3.80–5.40 mm, ♀♀ 3.90–5.95 mm); rostrum in lateral view stout, almost evenly curved, approximately of the same width from base to apex, its apical part in dorsal view with parallel sides, not narrower in midlength; antennal insertion in males closer to rostrum midlength; pronotum with almost conically narrowed sides; elytra with sub-rounded sides, short (length/width ratio usually less than 1.25), with the integument concealed by densely distributed scales, without rows of erect setae-like scales; anterior onychia in males of normal length, at most as long as tarsomeres 1 to 3 combined (
This is a widespread species in central and southern Europe and Asia. Its distribution extends from Portugal and Spain to Anatolia, Transcaucasus, Middle East, central Asia, western China (Xinjiang), Afghanistan, and Pakistan. Cionus olivieri does not occur in northern Europe, northern and eastern Asia, or North Africa (
Host plants of Palearctic Cionus usually include Verbascum, Scrophularia, Buddleja (Scrophulariaceae) and Limosella (Plantaginaceae) (
The aim of the present study is to describe the larva of C. olivieri in detail for the first time, in order to provide further characters for the identification of this taxon, and to compare this larva with the larvae of other species of Cionus, Cionini, and the apparent sister tribe Mecinini Gistel, 1848.
Fifteen mature larvae from Kyrgyzstan (Beshtash, Talas State, 42.391391°N; 72.279285°E, 1546 m, Verbascum songaricum, 2-VII-2018, leg. Chunyan Jiang) and 6 mature instar larvae from Kazakhstan (Altyn Emel Conservation Area, 44.18862°N; 78.51847°E, 1577 m, Verbascum songaricum, 12-VIII-2018, leg. Chunyan Jiang).
All described specimens were fixed in 75% ethanol and examined under a Nikon SMZ 1500 optical stereomicroscope with calibrated oculars. To prepare microscope slides, we made dissections as in
The observations and measurements were conducted using a compound microscope with calibrated ocular lenses (Leica DM 2500). The following dimensions were measured for each larva and provided in the Description: head width and length, body length (larvae fixed in a C-shape were measured in segments), and body width in the widest place (i.e., metathorax or abdominal segments I–IV). The relative lengths of all setae can be seen in the figures. Transparent structures were stained with Chlorazol Black E for further examination.
Photos of larvae were taken with a Canon-5D camera mounted on the microscope. Images of adults were photographed with a CCD Qimaging MicroPublisher 5.0 RTV mounted on a Zeiss SteREO Discovery. V12 microscope. Images from microscopic slides were taken with a Nikon CoolPix 5400. Photographs in the field were taken with Canon G15 camera.
Drawings were made from the original photographs using the software Adobe Illustrator CS6. The numbers of setae in bilateral structures are given for one side only.
We used the terms and abbreviations for the setae of the mature larvae found in
Cionus olivieri
Rosenschoeld, 1838: 725.
Figures
General. Body subcylindrical, C-shaped, weakly curved, extremely soft, declivous and attenuate posteriorly (Figs
Coloration. Head dark brown, very strongly sclerotized (Figs
Vestiture. Thoracic and abdominal segments with some minute and relatively long setae, cuticle minutely spiculate, pleural lobes distinct.
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).
Head capsule (Figs
Antenna (Fig.
Clypeus (Fig.
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).
Mouthparts (Figs
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.
Thorax (Fig.
Abdomen (Figs
The biology of this species was studied on Verbascum sinuatum in southern France by
We collected larvae of Cionus olivieri (Fig.
Later, we collected larvae of Cionus olivieri (Fig.
The larvae of eight Cionus taxa have been previously described (
The mature larvae of the genus Cionus are probably characterized by three diagnostic features: the reduced number of setae (1) on the epicranium (only two or three des and one or two fs), and (2) on the epipharyngeal lining (only two als, two ams, and no mes), i.e., distinctly fewer than the most frequent number of setae in weevils, and (3) mandibles dentate or angulate internally near the base (for details, see
The count of setae on the epipharynx (especially ams and mes) in Curculionidae has not been completely resolved, but this has been discussed in previous papers (e.g., Tychiini:
The abdominal spiracles in Curculionidae are located mainly on the spiracular area, but we observed their position more ventrally up to the ventral side of the epipleurum in Cionus olivieri. A similar position of the spiracle in Cionus species is also shown on the drawings of
With regard to the other genera of the tribe Cionini, only the immatures of three species were previously described, one belonging to Cleopus and two to Stereonychus (
Since it was hypothesized by a phylogenetic study based on morphological characters of imagos that the tribe Cionini might be the sister group of the tribe Mecinini (
We realize that a thorough study of the immatures of the genus Cionus and related genera and tribes is still impossible because of limited available knowledge. However, it is clear that a detailed description of immature stages is of primary importance for further studies on generic and intergeneric taxonomic relationships within Cionini and/or Curculioninae, as done in other groups of Curculioninae, such as Tychiini (
We are very grateful to Dr Jalil Chakaev and Dr. Zhildyz Agimberdieva (Institute of Zoology, Kyrgyz Academy of Sciences), and Dr Roman Jashenko and Mrs Viktoriya Lina (Institute of Zoology, Kazakhstan Academy of Sciences) for their kind help in collecting in the field; our thanks also to Dr Zhenyu Li (Institute of Botany, Chinese Academy of Sciences) and Dr Shimin Duan (Xinjiang Institute of Ecology and Geography,