Coccinella septempunctata Linnaeus, 1758
Native to the Palaearctic region from the tundra to northern Saharan Africa this species now occurs throughout Asia and the Middle East as well as North America and Canada. It has also been introduced to various areas either accidentally through trade or as a biological control agent e.g. it is now established in Hawaii, Madagascar and the Northern Neotropical region. Deliberate introductions have not always been successful e.g. several attempts to establish the species in the United States during the 1950’s and 1960’s failed but a population discovered in New Jersey in 1973, apparently an accidental introduction, spread rapidly and is thought to be the origin of the Nearctic population. It is now the ‘official state insect’ of several American states. This species was formerly one of the commonest ladybirds throughout Europe from lowlands to mountain areas, including the U.K., but a recent and drastic decline has occurred, in common with several other ladybirds, which is thought to be due to competition from the invasive Asian harlequin ladybird. It occurs throughout the U.K. and remains locally common in many areas, especially in the south, although in nowhere near its former abundance. In ‘good’ years with an abundance of aphids and favourable weather conditions the seven-spot may swarm in huge numbers e.g. during the very hot drought year of 1976. Adults are active early in the year, generally from the middle of March, and may be seen on emerging low foliage in just about any situation e.g. all types of woodland, parkland, dunes, moorland and gardens etc. and will occasionally take flight in warm spells. They are soon common and may be swept from vegetation wherever aphids occur in abundance, hedgerows in agricultural situations sometimes host large populations and during late spring and summer they occur among developing crops. Mating occurs during May and June although some individuals of the new late summer generation will mate in the autumn and here the females will store the sperm through the winter and their eggs will be fertilized in the spring along with the rest of the population. Each female lays between 250 and 500 eggs in small batches of 15 or so among low herbage rich in aphids although it seems they can detect the presence of other eggs as they will not oviposit in areas already hosting them. Both adults and larvae predate aphids and other small insects and their eggs but when these become scarce adults will feed upon pollen and larvae
will become cannibalistic. Depending on temperature the larvae hatch in between 2 and 10 days and consume at least part of the chorion before moving away to predate aphids; development is rapid and as they grow they change from sucking liquids from aphids to consuming entire insects. There are four instars and the time it takes for each to develop depends upon food supply and temperature but in general the larval stage will last for between one and four weeks. Before pupation the fully grown larva stops feeding and attaches itself to a leaf or stem or, commonly, under a windowsill or fence rail etc. In ‘good’ years the conspicuous pupae will be seen throughout the summer, with adults increasing in number from July or August as the new generation joins the existing one, the adults live for one or two years and may pass a second winter. There is generally a single generation in the U.K. although in Europe a second is not unusual. When threatened or handled the adults may ‘play dead’ and remain still in the sweep net or ‘reflex bleed’ producing a pungent orange fluid from the leg joints. Adults overwinter low down, among tussocks or under logs or stones etc. or may enter sheds and houses, they generally form groups of 10 to 15 but occasionally larger aggregations occur, sometimes along with other ladybird species. While gathering to overwinter they emit a pheromone to attract others to the group, presumably ensuring there will be plenty of beetles to mate with in the spring. In common with other ladybirds they can find aphids by detecting chemicals released from damaged leaves and stems or by following aphid alarm pheromones.
A large and glabrous ladybird, 5.5-8mm, of characteristic broad-oval form, the seven spot ladybird soon becomes distinctive. The head is dark with pale macula beside the eyes. Legs and palps black, antennae brown with the basal segment black. The pronotum is black with square pale macula inside the anterior angles. Elytra with a common dark scutellary spot and a pale area between this and the base, each with 3 black marks which vary in size but are only very rarely joined. It is thought that the size of these markings and the elytral colouration can provide some indication of the toxicity of an individual. A fully melanic form, f. anthrax, is very rare. Underside black with white mesosternal epimera. The scarce seven spot ladybird has the metasternal as well as the mesosternal epimera white.