Exochomus quadripustulatus (Linnaeus, 1758)
Exochomus is a small genus of 16 species native to Europe, the Near East and Southern and Eastern Africa. Nowadays, following introductions, intentional and otherwise, the genus has a worldwide distribution. None are native to the U.S.A. but 2 have been introduced as biological control agents. 11 species occur in Europe included in 2 subgenera:
-Exochomus s.str. with 4 species.
-Parexochomus Barovsky, 1918 with 7 species.
The genus is characterized by the following features:
-Postcoxal lines (which are usually almost semi-circular) do not reach the posterior margin of the sternum and are complete.
-Claws toothed at base.
A single widespread Palaearctic species, Exochomus quadripustulatus (Linnaeus, 1758), occurs in the U.K. and is generally known as The Pine Ladybird. This is probably the most widespread species having been introduced widely e.g. to Australia, where it is now invasive, and to the U.S.A. to help control the San Jose Scale insect, Diaspidiotus perniciosus, itself an invasive introduced accidentally in 1870 with trees imported from China. It is common throughout England and Wales north to Inverness including Anglesey and the Isle of Wight but apparently not from Man or the Western Isles. They occur in a wide range of habitats including deciduous and coniferous forests, mixed woodland, grassland, coastal dunes, cliffs, heathland and marshland. They are common in urban situations and often occur with other pine specialists as well as more generalist species e.g. the 2-spot, 10-spot, 14-spot and the Harlequin. Adults overwinter in pines generally; in sheltered bark crevices, in cones and leaf axils but also in leaf litter and bark crevices of other evergreen trees and shrubs e.g. Cedar and Broom. A south facing situation is usually chosen. They generally become active during April, depending upon the season, and will be found on pine at this time but if this is not available they will live on other trees and shrubs such as hawthorn, sallows and willows. Both adults and larvae feed on coccids, adelgids and other woolly aphids. Fourth instar larvae, which are usually present in late May or June, are distinctive; grey with 6 longitudinal rows of branched black spines and a wide white patch around the mid tubercle of the first abdominal segment. Pupation occurs on trunks or twigs etc., the pupa is black and shiny with brown markings on the thorax, and the shed larval skin is usually attached to the apex. Freshly eclosed adults are pale reddish but attain the mature colouration within 24 hours. Later in the year they seem to become more adventitious, we have recorded them from domestic gardens in Watford town centre in September and at m.v. light in the same area in August.
Among the U.K. epilachnid fauna these will be easy to identify, the colour pattern is distinctive and there is no spot fusion or melanism. Another species, Exochomus nigromaculatus (Goeze, 1777), has been recorded several times in the U.K. It will key to Exochomus but is distinctive with the elytra completely black and the head, pronotal margins and legs pale. On the continent this is a species of dry heathland. It was not recorded in the U.K. since the 1830’s until it was found near Doncaster (South Yorks.) in 1967.
Sub-oval and very convex. Black with distinctive red or orange markings to the elytra. Pronotal margin very narrowly, and front of head behind labrum and in front of eyes sometimes pale. Head including labrum very finely punctured and pubescent, with very fine microsculpture (x30). Genea expanded across front margin of eyes so hiding the antennal insertions. Pronotum glabrous, finely punctured and microsculptured. Side margin strongly bordered, front and hind margin without borders. Broadest at rounded hind angles. Front angles produced. Basal margin evenly rounded. Elytral puncturation stronger than that on pronotum, microsculpture weaker. Broadest about middle and evenly rounded. Side margin explanate to apex and continued around humerus. Underside black with visible sternites 2 and 3 broadly red laterally, and 4 and 5 completely red. Legs variously dark; tibiae to some extent pale, tarsi generally entirely so. Anterior tibiae without a tooth on outer margin.