Otiorhynchus (Pendragon) ovatus Linnaeus 1758

Otiorhynchus (Pendragon) ovatus (Linnaeus, 1758)

Material examined: 16 larvae (Fig. 217). JKI, Braunschweig, climate chamber, breeding in flowerpots with frigo strawberries (Fragaria x ananassa (West.) Duch. ex Roz.) and Fragaria vesca cultivar ‘Regina’, 13.12.2012, 2 ex.; 10.01.2013, 1 ex.; 29.04.2013, 4 ex.; 0 5.05.2013, 3 ex.; 19.05.2013, 3 ex.; 27.05.2013, 1 ex.

Remarks about breeding and development. All larvae used for the description were obtained from at least 1 breeding effort in the climate chamber of JKI. In 2011 only a few adults were released on 2 flowerpots with Euonymus fortunei and Fragaria vesca. The results were unsatisfactory as only Otiorhynchus sulcatus was obtained. In 2012 breeding was started at 2 dates in May 2012 and at one date in July. 8 weevils were released on 14.05. and 24.05. on 2 flowerpots with frigo strawberries and 2 with Fragaria vesca; on 25.07. 36 adult specimens and 1 flowerpot with Fragaria vesca and 5 pots with frigo strawberries were added to the breeding cage. The first mature larvae were taken out on 13.12.2012, but may have developed earlier, as on 0 1.11. this breeding had not been controlled. On 14.03.2013 1 flowerpot with many larvae was taken to Hannover for regular pupae control and revealed 1 pupa on 27.05.2013. Afterwards this breeding attempt was terminated.

In the field larvae of Otiorhynchus ovatus were found more or less by chance: 1 mature larva was collected on 29.03. 2011 in Bad Zwischenahn under Thuja occidentalis cultivar ‘Smaragd’ and revealed an adult weevil already on 26.04.2011. The pupa was seen first on 18.04., but the exact date of pupation is unknown.

The life-cycle of this species is rather well-known and was studied by Treherne (1914), Spessivtseff (1923), Wilcox et al. (1934) and Stein & Küthe (1969) in different regions and at different occasions. Treherne (1914) published the first life table, and Spessivtseff (1923) was the first who gave a detailed description of the larva. According to Treherne (1914) eggs were laid from mid-June to end of August, and larvae develop from late summer to spring, with a dormant period in winter, pupate from April to June, and young, at first light brownish adults emerge mainly in June and July on the soil surface. Usually adults die when the oviposition period is over, but according to Wilcox et al. (1934), at higher elevations a significant proportion overwinters and starts to lay eggs early in the season (in May). This widespread species is described as harmful in strawberry plantations (“Strawberry Root Weevil”) as well as in young conifer plantings.

Description (Figs. 122–132).

Coloration. Head light yellow; all thoracic and abdominal segments from white to yellowish; body covered with very fine cuticular processes.

Body elongated (Fig. 122). Chaetotaxy: Setae different in length, relatively long, filiform; white to yellow. Thorax. Prothorax with 4 long and 6 medium long to short prns; and 2 ps, different in length. Mesothorax with 1 medium long prs; 5 pds (ordered: 1 long, 1 minute, 1 very long, 1 long and 1 very long); 1 long as (sometimes with an additional microseta); 1 long eps; and 1 long 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. 123). Abdomen. Abdominal segments I–VIII with 1 short prs; 5 pds (ordered: 1 long, 1 short, 1 long, 1 short and 1 long); 1 long and 1 minute sps [abd. seg. VIII without sps]; 2 eps, different in length; 1 long and 1 medium long ps; 1 medium long lsts; and 2 eus (Figs. 124, 126, 127). Abdominal segment IX with 3 ds, different in length; 1 ps very long; and 2 sts, equal in length (Figs. 125–127). Lateral lobes of abdominal segment X with 2 minute ts each.

Head subglobose, narrowed bilaterally (Fig. 128). Head capsule with 4 long des, des 1 and des 2 placed on central part of epicranium, des 3 located on frontal suture, des 5 located anterolaterally; 2 long fs, fs 4 placed anteromedially, fs 5 located near to antenna; 2 long les; and 2 very short ves. Postepicranial area with a group of 2 pairs of sensilla, and frons with 2 pairs of sensilla. Stemmata (2 pairs) feebly visible. Antennal segment membranous, bearing 1 conical sensorium and 4–5 filiform sensilla. Clypeus 2.7 times as wide as long with 1 very short cls, placed posterolaterally (Fig. 129). Labrum about 2 times as wide as long with 3 long, straight lms of different length, placed medially or mediolaterally; lms 2 shorter than other setae, all lms exceeding the outline of the labrum; the anterior margin of labrum rounded (Fig. 129). Epipharynx with 3 finger-like als, different in length, 2 very short ams, different in length; and 2 very short mes; labral rods (lr) short, reniform, parallel (Fig. 130). Mandible (Fig. 131) feebly bifid, teeth almost of equal height; with 2 mds, different in length; internal edge with small triangular teeth. Maxilla (Fig. 132) with 1 very long stps and 2 very long pfs, placed ventrolaterally; 1 very short mbs, situated ventrally. Mala with 5 dms, different in length and 4 straight vms, different in length. Maxillary palpi with two palpomeres; basal palpomere wider than distal; basal palpomere with 1 mxps; distal palpomere with a group of 7 conical, cuticular processes apically; each palpomere with a sensillum. Praelabium heart-shaped (Fig. 132), with 2 short ligs and 1 long prms. Labial palpi with two palpomeres, relatively elongated; both palpomeres almost equal in length; praemental sclerite well visible. Postlabium with 3 pms, different in length; pms 2 very long, 2 times as long as pms 1 and pms 3 (Fig. 132).

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