|Otiorhynchus sulcatus (Fabricius, 1775)|
|So far not recorded from Orkney (Morris),
otherwise common and often all too common throughout the British Isles. British specimens are parthenogenetic;
males are unknown and reproduction is by unfertilized eggs (Gratwick, 1992). As well as occuring in a wide range
of wild habitats, the species is synanthropic, being found among cultivated plants both outside eg in orchards
and around herbaceous ornamentals and also under glass or in domestic situations where it is the predominant
weevil pest of potted plants. The common name (the Vine Weevil) derives from its european status as a pest of vines,
in the UK these are also attacked under glass. The species is polyphagous and may be found attacking a very
wide range of cultivated plants although in heated situations Cyclamen and Camellia are favoured hosts. Under
artificial conditions the adults begin to emerge in the autumn but egg laying does not commence until the
following spring and from then continues at intervals through the summer. Eggs are laid into the soil in pots
or seedbeds etc and the larvae remain in this habitat feeding upon roots while the adults eat leaves, causing
characteristic notches around the edges. Larvae from the earliest laid eggs can severely damage or, frequently,
destroy potted plants by late summer or autumn. The larvae, legless and with a curved, whitish body and brown head,
usually occur in numbers and are generally obvious when a plant is tapped out of a pot and the soil disturbed.
Plants showing areas of wilting despite adequate watering are often found to be hosting the species. Pupation
occurs in earthen cells; the large pale pupae are obvious. Adults may continue to emerge well into the winter
and larvae, pupae and adults may be found at the same time.
In wild situations the adults emerge from April onwards and at first spend much time on the ground, being active nocturnally. The first specimens to emerge are those that hatched from pupae the previous autumn and hibernating, winter is usually passed in leaf litter, typically under hedgerows or in woodland or gardens. These are succeeded through the summer by adults from overwintered larvae. Freshly emerged adults feed nocturnally on foliage for a few weeks before laying eggs in the soil near host plants. Strawberry plants are often attacked but here the adults must be taken and carefully examined as this plant is noted for hosting other weevil species eg O.clavipes (Bonsdorff), O.ovatus (L.), O.rugifrons (Gyllenhal), O.rugosostriatus (Goeze), Sciaphilus asperatus (Bonsdorff) and Barypeithes areneiformis (Schrank)(Strawberry fruit weevil). Eggs hatch within 8-24 days (Gratwick) and the larvae immediately begin to feed on roots. A small proportion of the early hatched larvae are fully developed by the autumn and burrow down into the soil to pupate and produce autumn adults but the majority of larvae overwinter, in various stages of development, and produce spring and summer adults. The life cycle takes between 9 and 18 months in the wild but less under artificial conditions.
The species is common throughout the Watford area. Specimens are occasionally swept from herbage in just about any situation and during the summer they are active nocturnally on parkland pathways but we encounter most specimens in domestic gardens and, more especially, around the town centre. From June or July we find them by sweeping domestic privet etc or, on the hottest days, they may be seen crawling on walls or pavements.
The broad and very convex, short oval form and white-mottled appearance will soon be recognised in the field.
7.5-9.5mm. Although very occasionally smaller specimens occur. Entirely black but for claws which are usually red. Immature specimens may be lighter, with legs almost entirely red. Upper surface, except for a densely microgranulate area at base of head, with sparse, backwardly recumbent and curved pale pubescence. Vertex of head finely punctured and with a well defined larger pit between eyes. Eyes weakly convex, cuticle behind eyes with fine transverse striations. Rostrum quadrate or nearly so, scrobes and antennal insertions visible from above. Scape gradually thickened apically, subparallel in basal two thirds. Funiculus 7 segmented; second segment much longer than first or third, 4-7 quadrate or nearly so, club narrow and pointed. Pronotum slightly transverse, sides evenly rounded and surface entirely tuberculate, tubercles glabrous and shining with pubescence lying in between. Elytra broad-oval with weakly developed shoulders and steep apical declivity. Upper surface with small groups of golden scales, mostly lying in striae. Entire surface with small shining black tubercles, those in striae much smaller than those on interstices, cuticle between somewhat dull, strongly microgranulate. Femora smooth, without tubercles, clearly toothed, all teeth with a single point. Front tibiae broadened towards apex on inner side only. Each tarsus with two claws distinct to base, not at all fused.
Description taken from many Watford specimens examined at X20.
Gratwick, M. 1992. Crop pests in the UK. Chapman and Hall