Phyllobius roboretanus Gredler, 1882
This species has a rather restricted distribution in Europe; it is generally common in central and southern regions from France to Austria but otherwise sporadic and very local, it extends north to Denmark and the UK and has been recorded from Algeria and (doubtfully) Siberia, it is locally common throughout England and Wales, less so in southern Scotland and Northern Ireland and there are scattered records north to Orkney. Adults are active from April until July or August, peaking in abundance during May and June, they are widely polyphagous and may be found on a wide range of herbaceous plants in most not too wet situations, typically grassland, roadsides and parkland, they may be common in domestic gardens and on coastal dunes etc. Mating occurs from April and females oviposit in the soil among roots on which the larvae will feed, larvae develop through the summer and pupate later in the year, adults are fully formed in the autumn but do not become active until the following year. The species is thought to be exclusively univoltine in the UK. Adults will occur when sweeping low herbaceous foliage and shrubs, in late spring and summer they are often common on small trees, especially birch, oak and beech, and they may occur in numbers among hawthorn blossom, which is a good way of finding mating pairs.
On average smaller than most green weevils at 2.5-4.5 mm, and easily distinguished among our other members of the genus by the combination of untoothed front tibiae, steep elytral declivity and the dorsal surface with dense round or slightly oval metallic scales (in fresh specimens.) Entire body black with metallic green or blue scales, appendages pale to dark brown, the legs femora and to a lesser extent the tibiae covered with scales. Head broad and almost parallel – sided behind convex and protruding eyes, rostrum short and almost quadrate, the scrobes straight in front of the eyes and variably covered with scales. Antennae long and slender, the scape curved and gradually thickened to the apex and the first two funicular segments much longer than the others. Pronotum transverse; broadest about the middle and narrowed to obtuse angles, the surface evenly convex and without structure. Elytra broader across the base than the base of the pronotum, with broadly-rounded shoulders punctured striae that are distinct among the scales, laterally almost parallel – sided in the male but distinctly dilated behind the middle in the female, apical declivity steep; towards the apex vertical or very nearly so. Abdominal sternites finely pubescent but lacking scales. Legs long and robust, all femora unarmed and the outer margin of the front tibiae sharply ridged. Females may be distinguished by the broader form of the elytra and less strongly sinuate inner margin of the front tibiae, also the second ventrite is smooth whereas in the male it has a distinct transverse keel.
Phyllobius roboretanus 1
Phyllobius roboretanus 2
Phyllobius roboretanus 3
Phyllobius roboretanus 4