POLYPHAGA Emery, 1886
CUCUJOIDEA Latreille, 1802
PHALACRIDAE Leach, 1815
Shining Flower Beetles
These convex and tiny beetles will soon be found by observing a variety of flowers, and with experience will become familiar and distinctive.
Around the World
This is a large family of more than 650 described species included in 2 subfamilies and about 50 genera. Many more specimens await description and this makes identification of species outside of Europe and North America very difficult. The greatest diversity is in the Old World tropical regions; 122 species in 12 genera occur in North America, 8 in Canada and about 60 in Europe. They appear to be absent from many of the Pacific islands as well as Chile. Only a single species, the invasive Phalacrus uniformis (Blackburn, 1980), is known from New Zealand. The species are morphologically well-defined and, despite their small size, soon become very distinctive. The vast majority are <4mm in length while a few tropical species just exceed 5mm. Most are rather drab coloured although there are exceptions e.g. members of the Nearctic genus Acylomus Sharp, 1888 have a pattern of pale macula and resemble certain Coccinellids. Many species are metallic. The subfamily Phaenocephalinae Matthews, 1899, originally classed as a separate family, contains only two species of Phaenocephalus Wollaston, 1873 occurring in Japan and Vietnam. In appearance they are typical of the family but here the tarsi are four segmented. The remaining species of the family are included within the Phalacrinae Leach, 1815.
They are convex and oval or broadly elongate with the pronotum and elytra broadest at the base and the underside flat. The front coxae are large and round or oval, the middle coxae separated by a broad and rounded mesosternal process and the hind coxae transverse and almost continuous. The front coxal cavities are open at the base. Most are glabrous and shiny with the upper surface variously punctured and microsculptured although this tends to be weak or only poorly developed. The head is usually transverse and retracted into the thorax at least to
some degree, with eyes that are weakly convex and usually follow the outline, the temples generally well-developed but usually mostly hidden. The antennae are usually long with the two basal segments enlarged and the three terminal segments form an elongate and flattened club, the morphology of which is often useful in identification. They are inserted into cavities in front of the eyes. In outline the pronotum and elytra usually form a continuous curve, both are very convex and lack any explanate margins. The elytra bear various incomplete striae, generally only one or two near the suture towards the apex, and there may be traces of others. It seems that most species are fully winged. The legs are short and robust with the tibiae generally bearing many small spines. Tarsi usually 5-5-5; segments two and three lobed, four tiny and the terminal segment long. Claws smooth but toothed at the base.
Both adults and larvae of many species feed on fungal spores and hyphae including Ascomycetes, ergot and smut or rust fungi. The adults of some feed on pollen while the larvae consume fluids within flower heads.
In the U.K. the family is represented by three genera and 16 species although the list includes Stilbus atomarius (Linnaeus, 1767), last recorded in 1946 and possibly now extinct, and Olibrus norvegicus Munster, 1901 recorded for the first time from Kent in 2012. The following description applies to our U.K. fauna. Elytra variously striate but always with one or two well impressed and incomplete sutural striae which are deepened towards the apex. Interstices microscopically punctured in most species. All our species are macropterous and at least some fly readily. Legs short; femora usually not visible in set specimens, protibiae with distinct terminal spines, the number and arrangement of which is sometimes diagnostic. Tarsi 5-5-5, segments two and three bilobed, and four very small so that they appear four segmented. Most species are black or brown although some species of Stilbus Seidlitz, 1872 are lighter red, brown or yellow towards the apex. Some specimens of Olibrus Erichson, 1845 are distinctly metallic. Identification to the generic level is straightforward but, because of the sometimes wide morphological variation, identification at the specific level may rely on an examination of the genitalia. Distinguishing the sexes on external morphology is often not possible but in some species the male may possess a more dilated second pro-tarsal segment, a distinctive terminal antennal segment or an emarginate anterior clypeal margin. Microsculpture will sometimes need to be examined but a magnification of at least X100 and excellent lighting will be needed.
Many of our species are widespread and common across the south of England and may be found by general sweeping. Examining flowers, especially yellow flowers, from late May or June onwards may produce them, often in numbers and generally among other beetles e.g. Meligethes sp. Many specimens will turn up by shaking flowers into bags or over a tray, the beetles often lay buried deep within the inflorescence and so flowers that seem devoid of specimens may give good results. After a while they become instantly recognisable, even in the field. Specimens occasionally come to u.v. light.
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