Halyzia sedecimguttata (Linnaeus, 1758)
This generally common ladybird occurs throughout the entire Palaearctic region from Portugal east to China and Japan and extending beyond the Arctic Circle in Fennoscandia but so far, perhaps surprisingly, has not become established in North America, throughout much of this range it is associated with deciduous and mixed forests, especially in drier areas, but across Europe it is also common in wooded parkland and gardens etc. In the UK it was considered for many years to be an uncommon and very local insect of ancient woodlands but there has been a considerable increase in both its range and abundance over recent decades and it is now generally common on broadleaf trees throughout the UK. Adults occur year-round, they overwinter under bark or, during the coldest spells, among leaf-litter and they have also been recorded in houses and sheds etc, they are active from April until October and may occur on various broadleaf trees in just about any situation, woodland, parks and gardens etc, and in the spring may common on hawthorn blossom. Various trees e.g. ash, elm, sycamore, beech and oak seem to be favoured but they will often be found on other species such as hazel , willow, lime and birch etc, both adults and larvae feed on powdery mildews (Erisyphaceae), particularly Phyllactinia guttata (Wallr.) and species of Podosphaera Kunze on the underside of leaves but they also occasionally take small aphids. Adults live for about a year and the life-cycle is thought to be univoltine but mating pairs may be found throughout the spring and early summer and the cycle is brief so there may be more than one generation each year. Eggs are laid in small batches on the underside of leaves and larvae generally emerge within a week, older larvae are strikingly coloured and unmistakable; the thoracic segments have four black spots arranged transversely, the prothorax is bright yellow while the meso- and metathorax are pale creamy grey, the abdominal segments also have four black spots arranged transversely but they are much smaller, the ground colour is creamy grey and there are two broad longitudinal bright yellow stripes, one either side of the middle, the head and legs are pale yellow or grey, the only confusion might be with the 22-spot ladybird larvae but here the head is brown and much darker than the rest of the body. Freshly emerged larvae are entirely pale grey with the pattern of black spots seen in fully-grown larvae, the yellow colour develops as they grow and can usually be seen, although sometimes only faintly, in the second instar. Pupation occurs on the underside of a leaf, usually near to the midrib, the pupa is also highly distinctive; shiny black with two bright-yellow spots on the first two abdominal segments and two dull-yellow spots on segments five to seven. Freshly emerged and soft adults may be found from June. Both adults and larvae are may be beaten or swept from foliage and adults frequently come to light.
Adults are large, 4.5-6.0mm, and bright orange with between 12 and 16 pale spots to the elytra though in the vast majority of specimens there are 16. The head is orange or yellow, the eyes are usually black, and the pronotum is orange with a longitudinal central line and two spots towards each edge yellow. The lateral margins of the pronotum and elytra are translucent and contrast with the ground colour.