|Two-spotted lady beetle|
Adalia bipunctata, commonly known as the two-spot ladybird, two-spotted ladybug or two-spotted lady beetle, is a carnivorous beetle of the family Coccinellidae that is found throughout the holarctic region. It is very common in western and central Europe and North America. It is used as a biological control agent.
The two-spotted ladybird was one of the many species originally described by Linnaeus in his 18th-century work Systema Naturae; its original name was Coccinella bipunctata. Its specific name is from the Latin bi- "two", and punctata "spotted".
The most familiar form of the two-spot ladybird beetle is the red one with the two black spots. However, there also exists a black form with red spots on it. In addition, there are intermediate forms, but they occur only rarely in nature.
Two-spotted lady beetles feed on aphids and other small insects. However, the sterile soldiers within colonies of aphids such as the gall-forming Pemphigus spyrothecae, can attempt to protect the aphid colony by fighting this species.
The two-spotted lady beetle's life cycle starts with eggs that are usually laid in clutches. The larva hatches from the egg by biting a hole in it. The larva looks very different from an adult: it has an elongated, grey, soft body with six legs but no wings. They are cannibalistic. A larva goes through four larval stages: by eating it grows and at some point it sheds its old skin and appears in a new one in which it can grow more. The last larval stage is approximately the size of an adult beetle. Once it has eaten enough, the larva attaches itself to a substrate and moults into a pupa. Inside the pupa, the adult develops. Finally the adult ecloses from the pupa.
Sex ratio anomalies
In some populations, the majority of the beetles are female. In these populations, 80-90% of the offspring of a female are female. The cause of this anomaly is the presence of symbiotic bacteria living within the gametic cells of the female lady beetles. The bacterium is too large to live in the male gametes (sperm), so the bacterium can be transmitted to the next generation only through female gametes. When it ends up in a male, it will die when the male dies. Therefore, it kills most of the male embryos in the newly laid eggs. These dead embryos then serve as food for their sisters when they emerge from their eggs. This trait is associated with a variety of different bacteria (Wolbachia, Rickettsia, Spiroplasma), which are present in between 0 and 20% of females, depending on locality.
The two spot ladybird also carries a sexually transmitted infection in Central and Eastern Europe. The infection is an ectoparasitic mite Coccipolipus hippodamiae that transfers between male and female (and female and male) during copulation. The infection sterilizes female two spot ladybirds, and at some points of the year, up to 90% of adult 2-spots become infected.
As biological control agent
A. bipunctata is used as a localised biological control agent against aphids in, for example, greenhouses.. The Two-spotted lady beetle was introduced into Australia specifically as a biological control agent.
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- (Latin) Linnaeus, C (1758). Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. Holmiae. (Laurentii Salvii).
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- Werren, J. H., Hurst, G. D. D.; Zhang, W., Breeuwer, J. A. J. et al (1994). Rickettsial relative associated with male killing in the ladybird beetle (Adalia bipunctata) 176. J Bacteriol. pp. 388–394.
- Insect Mol Biol. 1999 Feb;8(1):133-9. Invasion of one insect species, Adalia bipunctata, by two different male-killing bacteria. Hurst GD, Graf von der Schulenburg JH, Majerus TM, Bertrand D, Zakharov IA, Baungaard J, Völkl W, Stouthamer R, Majerus ME.
- Hurst GDD, Sharpe RG, Broomfield AH, Walker LE, Majerus TMO, Zakharov IA, Majerus MEN (1995) Sexually transmitted disease in a promiscuous insect, Adalia bipunctata. Ecological Entomology 20: 230-236
- Webberley K M, Buszko J, Isham V and Hurst G D D (2006) Sexually transmitted disease epidemics in a natural insect population. Journal Of Animal Ecology vol 75 issue 1 pp 33-43 ://000235043700004
- "Adalia bipunctata (Linnaeus)". www.ento.csiro.au CSIRO. 7 July 2005. Retrieved 2009-02-14.
- Data related to Adalia bipunctata at Wikispecies
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