With the exception of Hypera nigrirostris (Fabricius, 1775) our ‘green weevils’ are included in three genera within the Entiminae: Polydrusus Germar, 1817, Phyllobius Germar, 1824 and Pachyrhinus Schönherr, 1823. Hypera nigrirostris is included within the Hyperinae Marseul, 1863 and so is abundantly different from the others e.g. in the form of the rostrum and the deeply bifid scales, and with a little experience will be recognized on general habitus, it is included here not only because it is green but also because it is the same size as many of our other green weevils, is locally common across much of England and Wales and occurs in much the same habitats as some of our other green species and over a long season. During warmer periods of spring and summer Hypera is likely to occur alongside other green weevils when sweeping low vegetation and so it is as well to be aware of it from the outset. Most of our green weevils are polyphagous as adults and root-feeders as larvae, some are mostly arboreal or occur on herbaceous vegetation and many disperse widely during the spring and summer and so many will therefore be found in a variety of habitats and while most are generally common there are exceptions e.g. Phyllobius vespertinus (Fabricius, 1792) which is restricted to salt marshes along the eastern coast, but in general sweeping or beating vegetation in most habitats is likely to produce at least some species. Many species will also be found on various flowers, especially umbels and often in numbers on hawthorn blossom in the spring. A few will sometimes be found in very large numbers and some have been occasional pests of soft fruits and various horticultural products. In most cases they are very obvious in the field but they are prone to ‘rubbing’ and, especially later in the season, extensively denuded specimens are common. A brief overview of our species is given below but much more information is available through the links.
Orientation of scrobe in Polydrusus (top) and Phyllobius (bottom).
Although our genera are superficially similar they are easily separated on the form of the scrobes; in Phyllobius they are straight and, while often filled with scales, visible from the front margin of the eyes, the apical portion is also often visible from above along with the antennal insertions. In general Phyllobius are more robust than the others and have thicker antennae. In Polydrusus and Pachyrhinus the scrobes are placed laterally and so not visible from above; in side view they are obtusely angled about the centre and curve down in front of the eyes, a character well illustrated in Joy’s handbook. In most cases the sexes may be distinguished by the form of the elytra; in males it is narrower and often near parallel-sided while in females it is broader and distinctly widened about the middle. Pachyrhinus may be distinguished by the long and tapering head which is clearly convex behind the eyes and has a transverse glabrous ridge at the base of the rostrum, our Polydrusus species lack this ridge.
Pachyrhinus Schönherr, 1823
Pachyrhinus is a relatively small genus of mostly conifer-feeding weevils included within the Polydrusini, it is Holarctic in distribution with the greatest diversity, about 30 species in 3 subgenera, occurring in the Palaearctic region; ten species of the nominate subgenus occur in Mediterranean Europe although some of these have recently expanded their range, and three species occur in North America, all of which are associated with conifers, especially pine trees and they are sometimes known as pine-needle weevils. All species have fused claws and may be recognized by a prominent glabrous callosity across the base of the rostrum, a long antennal scape, prominent elytral shoulders and convex vertex, and dense covering of elongate green, reddish-brown or grey scales.
Pachyrhinus lethierryi (Desbrochers, 1875) is a Mediterranean species that has increased in range over recent decades, it was only recently discovered in the UK, from Hertfordshire in 2005, but has since spread across much of southern and central England and into parts of Wales and has become generally common. It is associated with various conifers and will often be found on cypress hedges, it is rarely found away from this host but, judging by the speed it has colonized just about every cypress hedge in South Herts., is very mobile and so may occur elsewhere during the warmer months. Adults feed on host foliage and their presence is often indicated by large areas of dead leaves and stems, they occur over a long season and are easily sampled in numbers by sweeping or beating. Another species, P. squamulosus (Herbst, 1795), which is widespread on pines and occasionally other conifers in northern and eastern Europe, was discovered in Surrey in 2004 but so far has not spread and remains only doubtfully established. P. squamulosus has smooth hind femora whereas in lethierryi they are toothed. Both species are thought to have arrived with horticultural stock from Europe.
Polydrusus Germar, 1817
Polydrusus is a Holarctic genus of about 200 species in 19 subgenera, the greatest diversity is in the western Palaearctic region and about 112 species of 18 subgenera occur in Europe, mostly in warmer southern regions, while 7 species are recorded from the United States and of these 4 extend north into Canada. They are generally absent further south but several extend into North Africa and the oriental region and a few are known from Central America, Mexico and the West Indies. Superficially similar to Phyllobius and Pachyrhinus but readily separated by the form of the scrobes, they are generally more elongate and slender and the genus includes more arboreal species, some of which are occasionally serious pests of fruit and nut trees, most are clothed in round scales which may be brown, grey, green or yellow and many are patterned or metallic, most have at least partially pale legs and antennae and the femora may be toothed or smooth. Unlike our Phyllobius species, all have the claws fused at the base. Most follow a typical lifestyle with adults occurring between March and September, adults may eclose in the autumn and remain dormant in the soil until the following spring or larvae may overwinter in the soil, complete their development in the spring and pupate in the soil to produce adults in the spring, either way mating occurs in the spring and larvae develop through the summer. Adults are generally polyphagous or oligophagous on broadleaf trees and shrubs but herbaceous plants are also attacked, and larvae develop in the soil, feeding externally on roots. Most are fully winged and can fly and while most are bisexual the genus also includes some parthenogenetic species.
Polydrusus marginatus Stephens, 1831 is a small wingless species associated with flightless species associated with a variety of trees and shrubs although often found in pitfall traps or among moss and litter at the base of trees, it is generally rare and restricted to a few areas in the south of England. The species can hardly be described as a green weevil, most specimens being grey or slightly metallic coppery, but viewed in bright sun at least some have a greenish tinge and so might be taken for a true green weevil. Distinguished by the rather narrow body and lack of prominent elytral shoulders, the antennae are more robust than in other members of the genus and have the distal funicular segments quadrate or slightly transverse.
P. mollis (Strøm, 1768) is a large (6.5-8.0 mm) and broadly-oval species with a narrow forebody and sloping elytral shoulders, it is generally metallic grey or coppery but distinctly greenish forms are not uncommon. The antennae are shorter than in most members of the genus and the femora are not toothed, the front and middle tibiae, and often the hind tibiae, have sharp external margins and the dorsal surface of the body is covered with hair-like scales. The species is locally common across England and Wales and adults occur on various trees and shrubs from April until August.
P. formosus (Mayer, 1779) was formerly a rare species in the UK but has spread over recent decades and is now locally common on a range of trees and shrubs throughout southern and central England and Wales. The shape of the head, broadest across the base and tapering to large and rather weakly convex eyes, will distinguish this species. The antennae are long and slender, pale with a dark club, the femora have a small ventral tooth and the tibiae are not sharp externally.
P. cervinus (Linnaeus, 1758) and P. pilosus Gredler, 1866 are dark species with a mottled appearance composed of patches of silvery or golden scales, some specimens have a distinct greenish hue but the mottled appearance is always obvious and will distinguish them from our true green weevils. P. cervinus is widespread and common throughout England and Wales while P. pilosus is a very local and generally rare species of northern England and Wales, Scotland and Ireland. Both occur on a range of trees and shrubs.
P. pulchellus Stephens, 1831 occurs on a range of herbaceous plants in salt marshes around the coasts of England and Wales. Most specimens are extensively greyish-green and many have contrasting longitudinal stripes of paler scales to the elytra but this varies and sometimes the greenish scales are only obvious around the margins, in any case the species may be recognized by partly or completely pale femora, broad pronotum and relatively narrow elytral base.
P. confluens Stephens, 1831 is widespread but local across much of England and Wales, it occurs on broom and gorse, mostly on heathland or near the coast, and may be abundant where it occurs. The colour varies from grey to coppery or even silvery, and in this sense it is not a green weevil but specimens often resemble P. pulchellus, often having paler strips of scales to the elytra. P. confluens may be recognized by the entirely dark femora but the habitat will be a good clue as to which species is present.
P. pterygomalis Boheman, 1840 is among the easiest of our green weevils to recognize due to a large swelling behind each eye. It is also among the most widespread and common of our green weevils, adults occur over a long season on various deciduous trees and shrubs.
P. flavipes (De Geer, 1775) is a widespread though very local and generally scarce species of England and Wales, it occurs on a range of deciduous trees and shrubs though rarely in large numbers and often only single specimens or pairs are found. Very similar to the next species but the head is slightly convex and lacks a median impression.
P. impressifrons Gyllenhal, 1834 was only recently (2012) discovered in the UK but it has become established and is spreading across the south of England, it occurs on a variety of trees but may be under-recorded because of similarities with the previous species. Here, as the name suggests, the head is impressed between the eyes but this is sometimes only slight and specimens may need to be examined carefully, and the vertex is slightly more convex when compared to flavipes.
Phyllobius Germar, 1824
Phyllobius is a large Holarctic genus of about 165 species of distinctive broad-nosed weevils included in 23 subgenera, the greatest diversity is in Asia but many species are widespread and the genus is well represented in Europe by about 66 species in 12 subgenera. There are no native Nearctic species but two introductions have become established and are now widespread: P. intrusus Kono, 1948 is native to Japan, and P. oblongus (Linnaeus, 1758) is a widespread Palaearctic species. Most are brightly-coloured and metallic but there are many exceptions e.g. P. oblongus, the only member of the subgenus Nemoicus Dillwyn, 1829, is a rather drab black and brown species lacking metallic scales. They are medium sized weevils, generally 6-10mm, oblong and rather parallel in shape with prominent shoulders and relatively long appendages. The head is smooth, lacking any striations behind prominent and convex eyes and the rostrum is short and broad, generally around 1.5 times longer than wide, the antennal scrobes and insertions are often visible from above and in lateral view they extend from near the apex of the rostrum to the anterior margin of the eyes. The antennae are long and slender and inserted near the apex of the rostrum. The pronotum is narrower than the elytra, quadrate or weakly transverse and widest about the middle giving most species a habitus that soon becomes familiar. The claws are connate. Many, if not all, species are fully winged. Most species are polyphagous or oligophagous on herbaceous and woody plants; the adults consume foliage while the larvae are subterranean, feeding on the host roots. In general they appear early in the year, mate in the spring and have a short season, the majority of species being gone by early summer. Occasionally they become very abundant in a particular area but none are particularly noted as pests. Larvae develop through the summer and it is thought that adults of most eclose in the autumn and overwinter in the soil.
Phyllobius roboretanus Gredler, 1882, P. viridicollis (Fabricius, 1792) and P. viridearis (Laicharting, 1781) have smooth femora, they are all small weevils associated with a range of herbaceous and woody plants and all are widespread and common. P. viridicollis is ‘only just’ green in that the body is substantially black with green scales only to the head and lateral pronotal margins.
P. vespertinus and P. pyri are distinguished by the combination of long-oval scales and sharply-ridged external margins to the femora. They are difficult to separate but vespertinus is restricted to salt marshes while pyri is among our most common weevils and is likely to occur in numbers in just about any situation.
P. pomaceus Gyllenhal, 1834 and P. glaucus (Scopoli, 1763) also have long-oval scales but lack the sharp tibial ridge. In general pomaceus has black legs while those of glaucus are pale but this can vary, they are superficially similar and differ in the form of the antennae and scales. P. pomaceus occurs on nettles while glaucus occurs on trees, often on alder, both are widespread and common and so reference material is easily obtained.
P. maculicornis Germar, 1824 is widespread and common on various deciduous trees and shrubs as well as a range of herbaceous plants; it is a striking green or yellowish-green species with strongly toothed femora long, robust antennae. Good clues to the species are dark club and apex to the antennal scape, striae which are obvious among the elytral scales and rows of small glabrous spots along the elytral intervals. Distinguished from the following species by the short, apically truncate setae to the elytra and lack of setae to the pronotum.
P. argentatus (Linnaeus, 1758) has distinct setae to the pronotum and longer, pointed setae to the elytral intervals. It is widespread and locally common throughout Britain and usually occurs on trees and woody shrubs, often on woodland borders and hedgerows.