Otiorhynchus (Choilisanus) raucus (Fabricius, 1777)

Rafał Gosik, Peter Sprick, Jiří Skuhrovec, Magdalena Deruś & Martin Hommes, 2016, Morphology and identification of the mature larvae of several species of the genus Otiorhynchus (Coleoptera, Curculionidae, Entiminae) from Central Europe with an update of the life history traits, Zootaxa 4108 (1), pp. 1-67 : 13

Otiorhynchus (Choilisanus) raucus (Fabricius, 1777)

Material examined: 8 larvae ( Fig. 204 ). JKI, Braunschweig, climate chamber, breeding with Prunus laurocerasus L. cultivar ’Rotundifolia’, dto., 13.11.2013, 1 ex.; dto., 24.01.2014, 1 ex.; dto., 0 1.04.2014, 2 ex.; dto., 0 9.05.2014, 2 ex. and dto., 19.12.2014, 1 ex.; dto., breeding with Thuja occidentalis L. cultivar ‘Smaragd’, 0 1.04.2014, 1 ex.

Remarks about breeding and development. Only rather few larvae of Otiorhynchus raucus were obtained from at least three breeding attempts in the climate chamber of the JKI in Braunschweig. In 2011 no larvae were obtained from breeding with Euonymus fortunei (Turcz.) Hand. -Mazz. In 2013 breeding was started on 10.06. with 18 weevils that were released on 2 flowerpots with Chaenomeles x superba (Frahm) Rehder cultivar ‘Hollandia’, 2 with Thuja occidentalis L. cultivar ‘Smaragd’ and 2 with Prunus laurocerasus L. cultivar ‘Rotundifolia’. In 2014 9 weevils were placed on 0 4.06. in 3 Prunus laurocerasus and 1 Fragaria vesca L. cultivar ‘Regina’ flowerpots. One flowerpot with Thuja occidentalis from the last year that contained no more larvae was added. The first mature larvae were obtained in 2013 in November and in 2014 in December, i.e. after 5 or 6 months, respectively. Also from the attempt in 2013 that revealed the highest number of mature larvae, no pupae could be obtained. In the field no larvae of O. raucus were found, which may be due to feeding sites deep in soil and perhaps to low or at most medium abundance.

The life-cycle of Otiorhynchus raucus is not well known. Early in the season, mainly in April and May, teneral weevils appear on the soil surface and start to lay eggs when sclerotized, from May or June, during the whole season until August and September. Adults overwinter in the pupal chamber deep in soil. Eggs laid late in the season should produce larvae that overwinter, too. Scherf (1964) confirmed the presence of overwintering larvae, but without giving any further information. Own attempts to find larvae in winter failed, but G. Kubach dug out even 8 not sclerotized, young adults on 26th January 2011 at the site with the highest abundance in Wiesbaden-Schierstein during the soildwelling weevils project of the Curculio Institute ( Sprick & Stüben 2012). Soil depth was around 50 cm. The pupa of O. raucus is still unknown.

Description ( Figs. 12–22 ). Coloration. Head dark brown; all thoracic and some first abdominal segments dark grey; remaining segments varying from grey to yellowish. Cuticle especially on the dorsal part covered by triangular cuticular processes and more pigmented than on the lateral and ventral parts.

Body elongated ( Fig. 12 ). Chaetotaxy. Setae different in length, filiform, greyish. Thorax. Prothorax with 5 long and 5 medium long to short prns; and 2 ps, different in length. Mesothorax with 1 short prs; 5 pds (ordered: 2 medium long and 1 long, and 2 medium long); 2 as, different in length; 1 eps; and 1 ps. Chaetotaxy of meso- and metathorax similar. Each pedal area of thoracic segments well isolated, with 5 pda, different in length. Each thoracic segment with 1 short eus ( Fig. 13 ). Abdomen. Abdominal segments I–VIII with 1 short prs; 5 pds (ordered: 2 short, 1 long, 1 short and 1 long); 1 long and 1 minute sps [abd. seg. VIII only with 1 microseta]; 2 eps, different in length; 1 long and 1 short ps; 1 medium long lsts; and 2 eus ( Figs. 14, 16, 17 ). Abdominal segment IX with 3 ds, different in length; 1 very long and 1 minute ps; and 2 sts, equal in length ( Figs. 15–17 ). Lateral lobes of abdominal segment X without seta.

Head subglobose, almost rounded ( Fig. 18 ). Head capsule with 4 relatively long des, des 1 and des 2 placed on central part of epicranium, des 3 located on frontal suture, des 5 located anterolaterally; 2 relatively long fs, fs 4 placed anteromedially, fs 5 located near to antenna; 2 relatively long les and 1 relatively long ves; all setae almost equal in length. Postepicranial area with a group of 4 pairs of sensilla, frons with 2 pairs of sensilla placed anteromedially. Stemmata absent. Antennal segment membranous, bearing 1 conical sensorium and 3–4 filiform sensilla. Clypeus 2.9 times as wide as long with 2 cls, equal in length, placed posterolaterally ( Fig. 19 ). Labrum about 2.5 times as wide as long with 3 straight lms of different length, placed medially or mediolaterally; lms 1 shorter than other setae, all lms exceeding the outline of the labrum; the anterior margin of labrum double sinuate; surface of labrum densely covered by triangular cuticular processes ( Fig. 19 ). Epipharynx with 3 finger-like als, different in length, 2 ams and 1 very short mes (see comments about ams and mes in Material and Methods); labral rods (lr) short, reniform, strong convergent ( Fig. 20 ). Mandible ( Fig. 21 ) feebly bifid, teeth almost of equal height; with 2 mds, different in length; internal edge with a triangular tooth. Maxilla ( Fig. 22 ) with 1 very long stps and 2 very long pfs, placed ventrolaterally; 1 very short mbs, situated ventrally. Mala with 7 dms, different in length and 4 straight vms, different in length. Maxillary palpi with two palpomeres; basal palpomere slightly larger than distal; basal palpomere with 1 mxps; distal palpomere with a group of 7 conical, cuticular apical processes; each palpomere with a sensillum. Praelabium heart-shaped ( Fig. 22 ), with 2 short ligs and 1 long prms. Labial palpi with two palpomeres, relatively elongated; basal palpomere slightly larger than distal; praemental sclerite feebly visible. Postlabium with 3 pms, different in length; pms 2 very long, 2 times as long as pms 1, and 3 times as long as pms 3 ( Fig. 22 ).

Differential diagnosis. See “Key to larvae of selected Otiorhynchus species” and Tables 1, 2.

Figures

FIGURES 203 – 210. Mature larva, lateral view. 203 — O. indefinitus, 204 — O. raucus, 205 — O. ligustici, 206 — O. sulcatus, 207 — O. porcatus, 208 — O. singularis, 209 — O. armatus, 210 — O. armadillo. (Photos by R. Gosik).

FIGURES 12 – 17. Otiorhynchus raucus; mature larva. 12 — habitus, lateral view, 13 — lateral view of thoracic segments, 14 — lateral view of abdominal segment I, 15 — lateral view of abdominal segments VIII – IX, 16 — ventral view of abdominal segments VIII – X, 17 — dorsal view of abdominal segments VIII – X. Abbreviations: Ab. — abdominal segment, Th. — thoracic s., I – X—number of segments, prns — pronotal seta (e), prs — prodorsal s., pds — postdorsal s., pda — pedal s., as — alar s., lsts — laterosternal s., eus — eusternal s., ps — pleural s., sps — spiracular s., sts — sternal s., ds — dorsal s.

FIGURES 18 – 22. Otiorhynchus raucus; mature larva and mouthparts. 18 — dorsal view of head, 19 — labrum and clypeus, 20 — epipharynx, 21 — left mandible, 22 — maxillo-labial complex. Abbreviations: des — dorsoepicranial seta (e), fs — frontal s., les — lateroepicranial s., ves — ventroepicranial s., at—antenna, st—stemmata, cls — clypeal s., lms — labral s., ams — anteromedial s., als — anterolateral s., lr—labral rods, mds — mandible dorsal s., dms — dorsal malae s., vms — ventral malae s., mxps — maxillary palps s., pfs — palpiferal s., stps — stipal s., mbs — mandible basiventral s., prms — prelabial s., pms — postlabial s., ligs — ligular s.