Meligethes Stephens, 1829
POLYPHAGA Emery, 1886
CUCUJOIDEA Latreille, 1802
MELIGETHINAE Thomson, C.G., 1859
M. atratus (Olivier, 1790)
M. flavimanus Stephens, 1830
This was formerly a huge genus that contained the vast majority of species included within the Meligethinae Thomson, C.G., 1859, the only other large genus being the mostly Afrotropical Pria Stephens, 1830, which includes about 75 species. The subfamily includes about 800 species, most of which were included in subgenera of Meligethes, but following a recent revision (Audisio et al, 2009) these subgenera are now considered to be valid genera and Meligethes s.str. now includes only 31 Palaearctic and Oriental species of which 3 occur in Europe: 2 of these, M. atratus (Olivier, 1790) and M. flavimanus Stephens, 1830, are very widespread and generally common throughout the region, including the UK, while M. denticulatus (Heer, 1841) is also widespread across Europe but does not extend to the UK. As well as established subgenera being raise to generic rank there are now 22 additional genera formed from groups within Meligethes and 43 genera are now recognized, of which 13 occur in the UK so that our fauna now includes 39 species in 14 genera (including our single member of Pria). Meligethinae is otherwise an essentially Old World group with many species in the Oriental and Afrotropical regions and a few in Australasia, it is Holarctic and although very diverse across the Palaearctic region, only 10 species of 6 genera are known from North America. The common name of pollen beetles is appropriate as so far as is known all species are anthophagous; adults spend much of their time within or upon flowers where many feed on pollen and nectar although some will enter unopened flowers and feed, and larvae develop within flower buds consuming the developing reproductive structures. Adults may occur on a range of flowers but larvae tend to be monophagous or oligophagous, many are associated with herbaceous plants but various trees and shrubs are also attacked. Adults overwinter and typically occur over a relatively long season from mid- or late-spring until late summer, they breed early in the season and are usually common by late spring, at which time many may be found on blossom and umbel flowers, and a few may be abundant at this time. Large numbers of specimens may be obtained by general sweeping but the vast majority will be Brassicogethes aeneus (Fabricius, 1775), this is a notorious pest of various brassica crops and a contender for our commonest UK species, but most specimens are (almost uniquely)metallic green and so can soon be ignored. At first anything that is not green should be examined carefully, and by sweeping a range of plants many common species will soon be found.
© Lech Borowiec http://www.cassidae.uni.wroc.pl/Colpolon/index.htm
Adults are very distinctive among our UK fauna and will soon be recognized even in the field; they are small, mostly between 1.5 and 2.5 mm, elongate-oval and rather depressed dorsally, most are black or dark grey with contrastingly paler appendages and very fine pubescence. General features are as follows. Head transverse, evenly convex above and produced in front of convex and often protruding eyes, antennal insertions widely placed anteriorly outside the base of the mandibles. Labrum freely articulated. Antennae short; basal segments elongate, the first much larger than the others, intermediate segments narrow, quadrate or transverse, and much narrower than the distal segments which form an abrupt and compact club. Pronotum transverse, broadest about or behind the middle and curved and narrowly explanate laterally, surface weakly convex, often uneven but usually without distinct structure. Elytra about as wide across the base as the base of the pronotum, widest about the middle and gently-curved to separately-rounded or almost truncate apical margins that leave the pygidium (at least) exposed, finely and randomly punctured and without striae although some have longitudinal impressions below the shoulders, lateral margins usually very narrowly explanate. Apical abdominal sternite with two broad semicircular impressions – this feature will distinguish all our genera from Pria. Front tibiae variously toothed externally, middle and hind tibiae with a single external keel. Tarsi 5-segmented, the basal segments distinctly lobed and the terminal segment long and gradually expanded to the apex. Identification can be very difficult at first as many species are superficially very similar and some vary in shape, some are distinctive and will soon be identified from external morphology but many will need to be dissected, external characters that will need to be appreciated in good detail are the overall shape, the form and density of the dorsal punctures and the form of the teeth along the external margin of the front tibiae. There are a few handy short cuts e.g. our 2 species of Acanthogethes have toothed tarsal claws, and some e.g. Meligethes, have entirely crenulate front tibiae, but most specimens will need to be examined very carefully. Meligethes, at least among our UK fauna, may be distinguished by the posterior pronotal angles which are slightly produced backwards, the presence of a short (and sometimes indistinct) subhumeral depression and the form of the front tibiae which are externally finely denticulate except for a few larger teeth before the apex. Both species are rather robust (at least for Meligethinae) but atratus is more elongate and less convex, it generally lacks a distinct pronotal reticulation which is always distinct in flavimanus, and often has paler explanate pronotal margins while flavimanus is usually entirely black. As with many species formerly included herein it is very often best to dissect specimens to be sure of the identity although a good reference collection will quickly be acquired and this can be a great help, more particularly as new species tend to be obvious against reliably named material. A very good guide for many of our species of Meligethinae is the host plant but this should only provide suggestions as adults tend to be more polyphagous than larvae. Fortunately our fauna is dealt with in very good detail in the RES handbook which provides genitalia figures as well as photos and SEMs (and lots of good ecological stuff) of all our species and should be considered essential to any study of our species.
Our 2 species of Meligethes are locally common across Wales and the south of England and extend sporadically further north, both are associated with various Rosaceae and may be found on both wild and cultivated roses. The following UK genera were formerly included in Meligethes and are briefly mentioned here to give an idea of the extent of our fauna.
Acanthogethes Reitter, 1871. 2 species, 6 in Europe. Associated with rock-roses (Helianthemum spp.) on calcareous grassland.
Afrogethes Audisio & Cline, 2009. 1 species, 5 in Europe. Associated with Viper’s-bugloss (Echium vulgare L.) on dry sandy soils.
Astylogethes Kirejtshuk, 1979. 2 species, 3 in Europe. Associated with various Campanulaceae.
Boragogethes Audisio & Cline, 2009 includes 3 European species, none of which are native to the UK but one has become established following recent introductions, it occurs on Comfrey (Symphitum officinale L.) and is very local and generally rare but seems to be spreading.
Fabogethes Audisio & Cline, 2009. 1 species, 4 in Europe. Associated with clovers.
Brassicogethes Audisio & Cline, 2009. 5 species, 26 in Europe. Associated with brassicas.
Genistogethes Audisio & Cline, 2009. 3 species, 6 in Europe. Associated with Fabaceae.
Lamiogethes Audisio & Cline, 2009. 11 species, 22 in Europe. On various Lamiaceae.
Sagittogethes Audisio & Cline, 2009. 4 species, 15 in Europe. On various Lamiaceae.
Stachygethes Audisio & Cline, 2009. 2 species, 9 in Europe. On various Lamiaceae.
Thymogethes Audisio & Cline, 2009. 3 species, 17 in Europe. On mint and thyme (Lamiaceae.)
Xerogethes Audisio & Cline, 2009. 1 species, 4 in Europe. Associated with various brassicas.