The Coccinellidae are a family of beetles, known variously as ladybirds (UK, Ireland, Australia, Sri Lanka, Pakistan, South Africa, New Zealand, India, Malta, some parts of Canada and the US), or ladybugs (North America). When they need to use a common name, entomologists widely prefer the names ladybird beetles or lady beetles as these insects are not true bugs. Lesser-used names include God's cow, ladyclock, lady cow, and lady fly.
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. has 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 recognize 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.
Coccinellids are typically predators of Hemiptera such as aphids and scale insects, though larvae and eggs of their own species can also be important resources when alternative prey are scarce.
Members of the subfamily Epilachninae are herbivores, and can be very destructive agricultural pests (e.g., the Mexican bean beetle). While predatory species are often used as biological control agents, introduced species of coccinellidae (such as Harmonia axyridis or Coccinella septempunctata in North America) out-compete and displace native coccinellids and become pests in their own right.
The main predators of coccinellids are usually birds, but they are also the prey of frogs, wasps, spiders, and dragonflies. The bright colours of many coccinellids discourage some potential predators from making a meal of them. This phenomenon is called aposematism and works because predators learn by experience to associate certain prey phenotypes with a bad taste. A further defense known as "Reflex bleeding" exists in which an alkaloid toxin is exuded through the joints of the exoskeleton, triggered by mechanical stimulation (such as by predator attack) in both larval and adult beetles, deterring feeding.
(Source: Wikipedia )
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