|Coccinella septempunctata (seven-spotted)|
- For the sports comedy movie, see Ladybugs
They are often called 'lady bugs' or 'ladybirds', but biologists prefer the term 'coccinellid' or 'lady beetle'.
Coccinellids are found worldwide, with over 5,000 species. Most species are insectvorous, feeding mainly on the true bugs, the Hemiptera. These are insects which feed on plants, such as aphids (greenfly) or scale insects. Ladybeetle larvae are also voracious (greedy) eaters of greenfly.
Harmonia axyridis (or harlequin ladybug) was introduced into North America from Asia in 1988 to control aphids. It is now the most common species there, out-competing many of the native species. It has since spread to much of western Europe, reaching the UK in 2004.
Defence[change | change source]
Coccinellids are often brightly coloured to warn potential predators. This phenomenon is called aposematism. It works because predators learn by experience to associate certain prey phenotypes (appearance) with a bad taste (or worse).
Mechanical stimulation (such as a predator attack) causes "reflex bleeding" in both larval and adult ladybird beetles. 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]
Most people know lady beetles as small, round, red beetles with black spots on their backs. In Europe, the most common lady beetle is seven-spotted Coccinella septempunctata.
Not all lady beetles are red, and not all red lady beetles have spots. Some lady beetles are very small, 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.
The (usually) black front part (pronotum) of the ladybeetle is the thorax and the head.
Life and food supply[change | change source]
Most coccinellids overwinter as adults. 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 ant herd aphids like sheep, and will attack a ladybeetle that tries to eat one of their aphids.
References[change | change source]
|Wikispecies has information on: Coccinellidae.|
- Judy Allen & Tudor Humphries 2000. Are you a ladybug?, Kingfisher, p30.
- 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.
- Anon. "The Harlequin Ladybird has landed!". The harlequin ladybird survey. Retrieved 17 June 2010.
- 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.