Coccinellidae - Overview

Overview

Coccinellids are small insects, ranging from 1 mm to 10 mm (0.04 to 0.4 inches), and are commonly yellow, orange, or scarlet with small black spots on their wing covers, with black legs, head and antennae. Such color patterns vary greatly however; for example, a minority of species, such as Vibidia duodecimguttata, a twelve-spotted species, have whitish spots on a brown background.

In some species the spots are so large that they merge, leaving the remaining bright colours as spots on a black background. Many coccinellid species are mostly, or entirely, black, grey, or brown and may be difficult for non-entomologists to recognise as coccinellids at all. Conversely, non-entomologists might easily mistake many other small beetles for coccinellids. For example the tortoise beetles, like the ladybird beetles, look similar because they are shaped so that they can cling to a flat surface so closely that ants and many other enemies cannot grip them.

Coccinellids are found worldwide, with over 5,000 species described, more than 450 native to North America alone.

The Coccinellidae are generally considered useful insects, because many species feed on aphids or scale insects, which are pests in gardens, agricultural fields, orchards, and similar places. However, some species do have unwelcome effects. Among these the most prominent are the subfamily Epilachninae, which are plant eaters. Usually Epilachninae are only mild agricultural pests, eating the leaves of grain, potatoes, beans and various other crops, but their numbers can increase explosively in years when their natural enemies are few, such as parasitoid wasps that attack their eggs. When that happens they can do major crop damage. They occur in practically all the major crop producing regions of temperate and tropical countries.

Harmonia axyridis (or the harlequin ladybird/bug) is an example of how an animal might be partly welcome and partly harmful. It was introduced into North America from Asia in 1916 to control aphids, but is now the most common species, out-competing many of the native species. It has since spread to much of western Europe, reaching the UK in 2004. It has become something of a domestic and agricultural pest in some regions and gives ecological cause for concern. It similarly has turned up in parts of Africa, where it has proved variously unwelcome, perhaps most prominently in vine-related enterprises.

A common myth, totally unfounded, is that the number of spots on the insect's back indicates its age. In fact the number, shape, and placement of the spots all are determined by the species of the beetle, and are fixed by the time it emerges from its pupa. The same applies to the colour, except that it may take some days for the colour of the adult beetle to mature and stabilise. Generally the mature colour tends to be fuller and darker than the colour of the callow.