Lady beetle

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Coccinellidae
Coccinella septempunctata (seven-spotted)
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Superfamily: Cucujoidea
Family: Coccinellidae
Latreille, 1807
Coccinella transversalis, elytra (wing cases) in the open position

Lady beetles are the Coccinellidae, a family of beetles. All species are protected by noxious fluids based on cyanide, and most have warning colouration, such as red with black spots.

They are often called lady bugs or ladybirds, but biologists prefer the term lady beetle.

Coccinellids are found worldwide, with over 5,000 species.[1] Most species are carnivorous, feeding mainly on the true bugs, the Hemiptera. Their favourite food is pests such as aphids (greenfly) or scale insects. Their larvae are also voracious (greedy) eaters of greenfly.

Harmonia axyridis (or the Harlequin ladybug) was introduced into North America from Asia in 1988 to control aphids but is now the most common species as it is out-competing many of the native species.[2] It has since spread to much of western Europe, reaching the UK in 2004.[2][3]

Defence[change | change source]

Coccinellids are often brightly coloured to warn potential predators. This phenomenon is called aposematism and works because predators learn by experience to associate certain prey phenotypes (appearance) with a bad taste (or worse).

Mechanical stimulation (such as by predator attack) causes "reflex bleeding" in both larval and adult ladybird beetles, in which a toxin is put through the joints of the exoskeleton, deterring feeding. This method works well; birds and cats seldom try twice.

Appearance[change | change source]

A scientific picture of the ladybug and its body parts
A ladybug's pronotum may sometimes be mistaken for the ladybug's whole head

Most people know lady beetles as small, round, red beetles with black spots on their backs.

Not all lady beetles are red, and not all red lady beetles have spots. Some lady beetles are very little and are black and hairy. Lady beetles vary in color as red, orange, or yellow with black spots. They can also be black with red spots. Some are missing spots altogether. There are even a few kinds of ladybeetles with metallic blue iridescence, and some have checkerboard markings or stripes.

Most of the black part of the ladybeetle is the thorax, also called the pronotum. It sometimes has spots on it, and sometimes it is all black.

Life and food supply[change | change source]

Ladybeetle larvae
Ladybeetle larvae look like strange adult insects

Most coccinellids overwinter as adults.[4] In Harmonia axyridis, eggs hatch in 3–4 days from clutches numbering from a few to several dozen. Depending on the supply of aphids, the larvae pass through four instars over 10–14 days, after which pupation occurs. After several days, the adults become reproductively active and are able to reproduce again, though not late in the season. Total life span is 1–2 years on average.

It only takes about four weeks for the ladybeetle to transform from a tiny egg to an adult. Some females can lay up to 1,000 eggs in one summer. The ladybeetle may lay her eggs near an aphid colony, or on plants where the larvae will have a ready supply of food when they hatch.

Almost all lady beetles are insectivores: they eat other insects. Many of these insects have soft bodies, such as aphids. Even the larvae eat other insects. Aphids are a huge problem for farmers and gardeners, and therefore a ladybug is a great help to the farmer. Some species of ants herd aphids like sheep, and will attack a ladybeetle that tries to eat one of their aphids.

References[change | change source]

  1. Judy Allen & Tudor Humphries 2000. Are you a ladybug?, Kingfisher, p30.
  2. 2.0 2.1 Anon (5 October 2004). "'Deadly ladybird' sighted in UK". BBC News (BBC). http://news.bbc.co.uk/1/hi/england/essex/3715120.stm. Retrieved 17 June 2010.
  3. Anon. "The Harlequin Ladybird has landed!". The Harlequin ladybird survey. http://www.harlequin-survey.org/. Retrieved 17 June 2010.
  4. A. Honek, Z. Martinkova & S. Pekar (2007). "Aggregation characteristics of three species of Coccinellidae (Coleoptera) at hibernation sites". European Journal of Entomology 104 (1): 51–56. http://www.eje.cz/pdfarticles/1197/eje_104_1_051_Honek.pdf.