Brachypera zoilus (Scopoli, 1763)
Originally native to the western Palaearctic region this species has become much more widespread through the trade in foodstuffs; it occurs commonly throughout Europe north to Fennoscandia and the UK and extends sporadically east to Japan, there are widely spread records from Africa e.g. Algeria and Ethiopia and it was first discovered in America in 1853, it has now become established and is widespread throughout the Nearctic region. Here it is locally common throughout England, Wales and Ireland and more scarce and sporadic further north to Orkney. Host plants include various species of lucerne, Medicago L. spp. and a range of both cultivated and wild clovers, notably meadow clover, Trifolium pratense L., white clover, T. repens L., alsike clover, T. hybridum L. and crimson clover, T. incernatum L., and it is occasionally recorded from other plants including wheat, Triticum aestivum L., maize, Zea mays L., artichoke, Helianthus tuberosus L., and burdock, Arctium lappa L. Adults occur throughout the year but are seldom seen during the warmest summer months as they enter the ground around the hosts and aestivate, they may occur in any open and well-vegetated habitat where the hosts are common; wasteland, grassland, commons and heaths etc. and, at least in the UK, they usually occur in small numbers. Both adults and larvae feed nocturnally on the upper parts of host stems and foliage; in the spring adults eat small holes into the leaves and stems, this is usually superficial but may cause fresh stems to die back; on the continent and, especially, in the United States where the species is a significant pest, clover fields may be severely infested and plants extensively damaged and eventually stop growing or die. Depending on when they eclose, adults may mate and oviposit in late summer or autumn and produce larvae which overwinter and continue developing in the spring, these pupate from March to give spring and summer adults, or adults that eclosed late in the year will overwinter and emerge to feed on developing host foliage and spend a few weeks maturing before mating, occasionally they will mate and oviposit during mild winter spells but
this is unusual in the UK. Eggs laid late in the year may also overwinter to produce larvae from early spring. Females are very fecund and each will lay up to 500 eggs over a long period among the host foliage and where the beetles are common repeated laying may produce eggs and larvae in various stages of development on the same plant, they may be common during the spring and mate from May onwards but will not oviposit until late summer or autumn and winter is passed mostly in early larval stages. Plants may thus be severely attacked during the spring when both adults and larvae are feeding; both stages remain in the ground beneath the host during the day and ascent the stems to feed at night. Fully-grown larvae enter the soil and construct a cell in which they pupate, this stage lasts about a week and adults emerge from the soil soon afterwards. Adults may occasionally occur during the day but the best way to sample them is by sweeping likely situations at night. The distinctive larvae may also be seen at night, they are legless and plump, green with a pale creamy stripe along the dorsal surface of the abdomen and they usually sit near the base of the leaves consuming them from the edges.
Adults are large and distinctive; 6-9mm and drab brown or grey with a central pale stripe to the pronotum and several on the elytra. Head smoothly convex with large eyes and a broad and relatively short rostrum, less than twice as long as wide, antennal scape smoothly broadened from the apical half, funiculus 7-segmented, club elongate but short and compact. Pronotum transverse and widest anterior to the middle, evenly narrowed laterally and much narrower at the base than the elytral base, usually with a mixture of pale and dark scales which may give an overall mottled appearance and usually with a distinct pale median line. Prosternum without a deep rostral channel. Elytra with well-developed shoulders and almost parallel-sided, with dense short and truncate scales giving a pale to very dark ground colour, odd-numbered interstices paler and, usually, with small patches of much darker scales. Interstices flat, finely punctured and with short semi-erect curved setae. Underside and lateral margins with extensive and dense pale scales. Legs long and robust; femora without a ventral tooth, apices of middle and hind tibiae simple, front tibiae only indistinctly produced internally at the apex, tarsal claws free.