|Strophosoma melanogrammum (Forster, 1771)|
|A generally common species occurring throughout England, Wales and Scotland including the Isles of Wight,
Anglesey and Man (NBN Aug 09) and north to the Shetlands but not, apparently, from Orkney (Morris, 1997).
Typical habitat is woodland, wooded pasture, parkland, hedgerows and gardens. The species is polyphagous and
occurs on a range of broadleaved and coniferous trees and shrubs although there may be a general preference
for Quercus (oak) and Corylus (Hazel) and they can be an important pest of commercially
growing conifers with perhaps a preference for Larix (larch); adults damage leaves and strip rings
of bark from young growing twigs so causing them to die back (Bevan, 1987). Larvae feed on the roots of
various herbaceous plants. Locally the species occurs throughout our area in just about any wooded
situation; we have recorded the adults among samples extracted from grass tussocks from Cassiobury park in
December and January and swept them from long grass in the same locality from March onwards, they become
active on Quercus saplings from just before they come into leaf and once the sapling buds burst the
weevils are present in abundance, they seem to prefer the saplings and young trees to mature specimens.
From mid-April they may be swept or beaten from broadleaved trees throughout our area but, perhaps because
of the abundance of broadleaved species, we very rarely record them from conifers. They remain abundant
until late in the year persisting on Quercus saplings after the foliage has turned brown and begun
to fall; according to Phillips (1992) numbers of adults peak during September and October. Numbers fluctuate
from year to year eg they were abundant everywhere in 2007 but much less so in 2008 and 2009, but even when
numbers are 'low' they may still best be described as common.
This species soon becomes obvious in the field; the globose form, dull metallic colour and bare, shiny cuticle at the base of the suture are characteristic.
4-6mm. Body black, appendages ferrugineous; upper surface covered with small, round and dull metallic brown or bronzy scales. Basal third or so of suture devoid of, or almost devoid of, scales, formerly thought to result from abrasion during mating but the species is almost certainly partenogenetic (Morris), males have not been recorded in the UK; older records of males refer to other widely misidentified species. Scales on head may be dense but this is often widely denuded, with broad, erect curved scales evenly distributed among the recumbent scaling, these may also be extensively denuded. Eyes exceptionally conex, vertex behind eyes raised above the neck by a transverse step. Upper surface of head with (sometimes obscure) longitudinal ridges from basal step to upper surface of rostrum, transversely impressed in front of eyes. Rostrum quadrate, tapering anteriorly. Scobes deeply impressed; in side view sinuate and terminating below eyes. Antennae inserted towards the end of rostrum. Scape curved at base and abruptly clubbed at apex, funiculus 7-segmented; 1 and 2 elongate, 3-7 quadrate, club narrow, elongate and pointed. Pronotum transverse (average 33:25), surface densely scaled but large pits and a central longitudinal impression are usually discernable, generally with an ill-defined longitudinal strip of paler scaling either side of middle, this paler colour is continued onto the base of the elytra. Without lateral borders and broadest in front of middle, entire surface with short, broad and curved upright scales (obvious at X20), as head. Elytra very convex, basal margin much wider than base of pronotum and with wide, rounded shoulders. Striae strongly punctured. Interstices with a row of long, semi erect, broad and truncate curved scales, these become larger towards apex. Sometimes there are distinct longitudinal lines of pale scales towards the side margins. Legs long and robust. Femora without ventral tooth, densely scaled. Tibiae without terminal spurs.
Description from 16 Watford specimens at X20
Bevan, D. 1987. Forest Insects. Forestry commission handbook 1. HMSO publications
Phillips, W.M. 1992. Assemblages of weevils in the lower tree canopy of a mixed temperate woodland. The entomologist III (2) 61-78.