|Involvulus cupreus (Linnaeus, 1758)|
Photograph by Clive Washington, specimen verified by Don Stenhouse.
A widespread although very local weevil occurring throughout England and Wales and into Scotland to Perth and
Argyll. We have not recorded the species from our Watford area but its presence should not be entirely
unexpected; the NBN (Oct 2009) shows records from south of the Thames and the midlands, the image featured
is from a specimen from Bickerton hill, Cheshire and was photographed and kindly given to us by Clive
Washington. The hostplant, mountain ash (Sorbus aucuparia), is very common throughout our area.
Fowler also quotes whitethorn, apple and sloe etc but these are only rarely recorded as hosts in the UK
(Morris). Larvae develop in the fruits and
adults may be found on the flowers (Fowler quotes adults in July).
A relatively large and distinctive species. 4-5mm. Upper surface colour may vary a little from that pictured, rather strongly metallic. But for the rostrum the entire surface and legs are clothed in pale and fine, rather erect pubescence. Underside dull metallic black. Head densely punctured, eyes entire, moderately convex. Temples not narrowed towards base. Rostrum longitudinally sulcate towards base; in male as long as pronotum, in female almost as long as head and pronotum combined. Pronotum slightly transverse, gradually narrowed to anterior margin. Without lateral borders, anterior and basal margin finely bordered. Surface strongly and densely punctured, more densely so than head, and with a smooth longitudinal median line - this is variable and may be almost obliterated by puncturation. Elytra slightly elongate (about5:4), broadest behind middle and entirely rounded to apex. Striae entire, strongly and deeply punctured. Interstices finely punctate and rugose. Pygidium usually exposed; the elytra cover the pygidium.
The genus Involvulus Schrank, 1798 may be distinguished from our other Rhynchitid genera by the following combination of characters: length 3.5-5mm, upper surface pubescent throughout, head not constricted towards base and elytra with regularly punctured striae from base but lacking an abbreviated scutellary stria. Two specie soccur in the UK and are readily separated:
4.0-5.0mm. Upper surface dark metallic bronze to coppery or reddish (described by Fowler as 'obscurely purplish-aeneous') Pubescence shorter.
cupreus (L.)2.5-4.0mm. Upper surface bright blue to dark blue black, sometimes with a greenish tinge, head and pronotum sometimes darker. Pubescence long.
Twig cutting weevil coeruleus (De Geer)