Brassicogethes viridescens (Fabricius, 1787)
This generally common and often abundant Western Palaearctic species occurs throughout Europe north to the UK and central Fennoscandia, it is widespread across northwest Africa and extends east through Turkey, northern parts of the Middle East, Iran, western Russia and the Caucasus as far as Kazakhstan, it is common on most of the Mediterranean islands and has also been recorded from Iceland. Beyond this there are more widespread records e.g. from northwest China, but these may not represent part of the natural range, and it was first recorded from the Nearctic region in 1993 and has since become established in several coastal localities in Maine and Nova Scotia. In the UK it is widespread but rather local across England and Wales north to the Humber though less so in the West Country and further north to southern Scotland, there are modern records from the northern Scottish Highlands and Ireland; it was formerly common throughout much of this range but seems to have suffered a drastic decline over recent decades and is now much less frequent. The species is associated with a wide range both wild and cultivated Brassicaceae, in Europe it is sometimes a serious pest of spring sown crops such as summer rape (Brassica napus L. and B. rapa L.) and in North America it occurs on wild radish (Raphanus raphanistrum L.), in the UK it was once common on rape crops along with B. aeneus (Fabricius, 1775) but is now more or less vanished in this situation. More generally it may be found on yellow flowered-species of Brassica L., Cardamine L., Arabis L., Sinapis L. and Erucastrum (DC) C. Presl, all of which are hosts, and may be common on wild mustard (Sinapis arvensis L.) or black mustard (B. nigra L.). The lifestyle is typical of the family with reproduction occurring in spring and early summer and females ovipositing in unopened flower buds where the larvae will consume pollen and flower parts and pupate in situ to produce adults from early summer that will go on to overwinter. Adults become active early in the year and those of the new generation persist into the autumn, they are pollen feeders but also eat into flower buds, destroying them in the process, in this respect they are widely polyphagous and occur on flowers of a range of plant families, e.g. they may be found on buttercups (Ranunculaceae), daisies (Asteraceae) and various umbels (Apiaceae) and are sometimes common on hawthorn and other blossom in the spring. Typical habitats are wherever the host plants grow in abundance but they fly well and so may occur in any situation during spring and summer.
2.0-2.9 mm. Elongate-oval and moderately convex, body entirely metallic green to blue or with the lateral pronotal and elytral margins narrowly brown, dorsal pubescence short and fine, legs brown, antennae dark with several basal segments pale. Head flat between convex and protruding eyes, strongly narrowed anteriorly to a straight anterior clypeal margin, and surface very finely and rather densely punctured. Pronotum broadest in the basal half and narrowed to projecting anterior angles, posterior angles almost perpendicular and not produced backward, surface weakly convex between narrow explanate margins, punctures across the disc deep, about as wide as an eye facet and separated by a little more than their diameter. Elytra smoothly curved from minutely-toothed shoulders to a continuous apical margin, surface only vaguely impressed about the base and without a distinct subhumeral impression, punctures simple and discrete, never forming a transverse strigosity. Posterior margin of the middle femora with a broad tooth in the apical third, this will separate the present species from the closely similar M. aeneus (Fab.) External margin of front tibiae toothed throughout, these are tiny in the basal half to two-thirds and then become gradually larger towards the apex. Median lobe of male genitalia parallel-sided in the basal half then gradually narrowed to a more-or-less truncate apical margin, tegmen with a deep and straight-sided V-shaped excision apically. Males may be recognized by their expanded basal front tarsal segments.