Phyllotreta undulata Kutschera, 1860
A widespread and generally common species throughout Europe, extending east through Asia Minor and Russia to Mongolia and the far east of Siberia and China, to the south it occurs in North Africa and to the north throughout Fennoscandia and the UK, it has also been introduced and become established in North America, Canada, Australia, New Zealand and many oceanic islands. Here it is common throughout England and Wales including all the islands and rather more local and scarce to the north of Scotland and across Ireland. Adults may be swept from herbage in a wide range of habitats including woodland, roadsides, hedgerows, grassland, salt marshes, gardens and arable land etc., they occur year-round and are active from early spring into the autumn, peaking from May to July. Host plants include both wild and cultivated Brassicas as well as various other plants including sea beet, nasturtium, brooklime and wild mignonette, adults feed on foliage causing numerous small holes and may also feed within the flowers consuming pollen. Reproduction occurs through the spring and oviposition begins in May and continues into the summer, eggs are laid in the soil at the base of host plants and larvae emerge within two weeks. Larvae feed within the roots, they develop rapidly and are fully-grown within three weeks when they enter the soil and form a cell in which they pupate, this stage lasts about three weeks and new-generation adults emerge from early summer. There is a single generation each year; adults overwinter in tussocks or among moss or leaf-litter, under debris or bark or among decaying vegetation or hay. Sampling is straightforward, adults may be swept from suitable vegetation or attracted to yellow pan traps, they fly well and have been recorded in flight-interception and malaise traps, during the winter they appear in extraction samples of tussocks and hedgerow debris etc. and in the spring they disperse and might occur in any situation where the host occurs. Very large populations occasionally occur and throughout its range the species has occasionally been a serious pest of various Brassica crops, similarly they may occur in large numbers in domestic gardens and allotments, for this reason a great deal of information about the life-cycle and development can be found online.
Phyllotreta undulata 1
Phyllotreta undulata 2
This species will soon become familiar by the form of the pale elytral stripes and the bicoloured legs. 2.0-3.0mm. Body entirely black, often with a weak metallic reflection, each elytron with a longitudinal yellow band than narrows medially and curves towards the suture around the apex, the black sutural stripe gradually widening from the base to the apex where it is constricted by the yellow band. Head very finely punctured, antennae black with the first three segments variously pale, sometimes only towards the apex or only ventrally. Pronotum widest near the base and evenly narrowed to a straight or only weakly curved anterior margin, basal margin very finely bordered and the surface strongly and moderately densely punctured. Elytra with distinct shoulders, broader across the base than the base of the pronotum, evenly rounded laterally and continuously curved apically, surface randomly punctured, a little less strongly so than the pronotum. Legs dark but for the base of the tibiae and the tarsi variously pale. Males may be distinguished by the dilated basal pro-tarsal segment and modified antennae; the fourth segment is slightly wider than the third and the fifth is distinctly broader than the fourth.