Coccinellidae | UK

COCCINELLIDAE Latreille, 1807

Ladybirds

This family includes some of the most familiar insects in the UK, most are very distinctive and instantly recognizable. Different species are associated with a wide variety of habitats.

POLYPHAGA Emery, 1886

CUCUJOIDEA Latreille, 1802

Approx. 50

1.1-9mm

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Introduction

With more than 5000 described species the ladybirds are a cosmopolitan and generally striking group. They are small to medium sized beetles, 0.8-18mm, which are very variable in detail regarding colour and shape but nonetheless very characteristic and recognizable. Generally considered useful because many species feed on species of aphid or scale insect which are agricultural or horticultural pests. Many have been used in orchards and arable situations as biological control agents. Some species of epilachninae can be minor pests because they are phytophagous, eating the leaves of grains, potatoes and beans etc. but their numbers can increase greatly in response to climate or parasite numbers and then they can do severe damage. Ladybirds occur in all the main crop producing regions. Although most species are noted as aphid and scale insect predators they also take a much wider range of prey; larger species attack caterpillars and other larvae. Coleomegilla maculata DeGeer, 1775, from the U.S.A., is a predator of lepidopteran eggs and larvae. In the absence of sufficient prey coccinellid larvae may predate the larvae of other ladybird species. Gut content analysis of apparently specialist predatory species often produces pollen, nectar, honeydew, sap and various fungi. Stethorus species are specialist spider mite predators and so are important in biological control. Some species are thought to lay extra, infertile eggs to provide a back up food source for the larvae when prey are scarce. Two of our UK species, Platynaspis luteorubra (Goeze, 1777) and Coccinella magnifica Redtenbacher, 1843 are associated with ants.

The main predators of ladybirds are birds, frogs, wasps, spiders, dragonflies and other beetles. Hymenopteran parasites are numerous and generally common. As well as aposematic colouration, ladybirds defend themselves by reflex bleeding and some species are protected by chemical means at various stages of development. Assembly is a well known phenomenon in ladybirds which may occur in response to lack of prey or prolonged hot weather. During the hot summer of 1976 in the U.K. an increase in aphid populations was followed by a plague of ladybirds with many reports of people being bitten due to dwindling aphid numbers.

The Harlequin ladybird is an example of an invasive species. It was introduced to the U.S.A. from Asia in 1916 to help control aphids and is now a common species, outcompeting many native species. It has since spread through Europe, including the U.K., and is spreading in parts of Africa. In the U.K. many species seem to be in decline (2015) although some, including the Harlequin, Orange, Pine and 24-spot are increasing. Several species have only recently been recorded in the U.K.; Rhizobius chrysomeloides is a recent addition and is now widespread.

Description

Size varies greatly, 0.8-18mm. But most are small and size variation within a species may be large. Many are brightly coloured and this may be very variable, often with named varieties and melanic forms. Body outline elongate oval to almost circular and many, or even most, are very convex. Many species are pubescent e.g. Scymninae and Epilachninae. The antennae are inserted close to the front margin of the eyes and the insertions may be hidden under an expanded lateral part of the frons. Usually 11-segmented, very rarely 10-, and with a 3-segmented club which is often poorly delimited. Mandibles are bidentate or, e.g. in the Epilachninae, have 4 or more apical teeth. Terminal segment of palps are securiform or subsecuriform. Eyes large and coarsely faceted, often notched behind the antennal insertions. In the chilocorinae the eyes are divided by the laterally expanded genae. Pronotum transverse and usually with strongly produced front angles. Prosternal process often with longitudinal lateral ridges or with a central furrow. Mesosternum short and often emarginate anteriorly to accommodate the prosternal process. Metasternum long, usually with raised plate-like processes behind the mid coxae. Abdomen with 5-7 sternites, the first usually bearing raised plates similar to those of the metasternum. Legs short and retractable into the undersurface. Tarsi 4-segmented, often appearing 3-segmented as the third segment is very small and partly hidden by the bilobed second segment. Some species, although none British, have genuinely 3-segmented tarsi. Claws simple, bifid or trifid, simple or lobed at base.

Larvae tend to be active insectivores, fungivores or herbivores. Mostly elongate, sometimes ovate and weakly to strongly flattened. Generally vividly coloured or cryptic against vegetation or substrate. Tergites frequently with tubercles or spines that may be simple or branched with setae or hairs. In wax covered species the tergal projections are absent. Legs generally long and slender. Head with 3 ocelli on either side.