Length: 5 - 8mm. Background colour: (1) ‘succinea’: yellow/orange/red; (2) ‘spectabilis’ and (3) ‘conspicua’: black. Pattern colour: (1) with 0-21 black spots; (2) with four red/orange spots/patches; (3) with two red/orange spots/patches. Number of spots: 0-21 (16). Spot fusions: common in ‘succinea’ form. Melanic (black) forms: common (‘spectabilis’ and ‘conspicua’). Pronotum: white or cream with up to 5 spots, or fused lateral spots forming 2 curved lines, M-shaped mark or solid trapezoid. Leg colour: brown. Other features: many specimens have a slight keel along the posterior margin of the dorsal surface; extremely variable in colour and pattern.
Fourth-instar larva: black, with thick dorsal spines coming from each tubercle, each branching at the top into three prongs; bright orange upside-down L-shaped marking on each side, made from middle tubercles of abdominal segments one to five and inner tubercles of abdominal segment one; two pairs of orange dots on dorsal surface, made from inner tubercles of abdominal segments four and five. Pupa: orange, with pairs of black squarish markings running down the second thoracic segment and abdominal segments two to six; remains of shed spiky larval skin visible at base of pupa.
Habitats: Harlequin ladybirds are noted for being habitat generalists. Like the 2-spot ladybird, the species is considered to be arboreal, and many records are from urban areas where deciduous trees are abundant. This species can be readily found on mature lime or sycamore trees, for example in churchyards and parks. However, harlequin ladybirds also occupy mature woodlands (both deciduous and coniferous), scrub, grassland, marshland and reed beds. Crops and orchards are common habitats for harlequin ladybirds. Harlequin ladybirds overlap with a number of other species of ladybird including 2-spot, 7-spot, 10-spot, 14-spot and pine ladybirds.
Host plants: The host plant list for the harlequin is diverse and extensive; however, it undoubtedly has a preference for lime and sycamore trees. It is also commonly associated with herbaceous plants such as nettle, thistles, cow parsley, rosebay willowherb and fat-hen. Harlequin ladybirds are common in gardens where they can be found on many ornamental plants.
Food: aphids, coccids, coccinellids.