Tuesday, May 24, 2011

Colour Changing Spider

Misumena vatia
Misumena vatia is a common crab spider (Thomisidae), one of 14 species of crab spiders in Ireland (1). Resembling crabs in their appearance and in their movements sideways and backwards, the larger females can be found sitting on flowers, waiting to pounce on prey such as hoverflies and bees that feed on the flowers (2). M. vatia is most often seen on white or yellow flowers and quite amazingly the spider can change its colour, chameleon like, to camouflage to its background (3). Colour change occurs over a period of days and this ability is due to the presence of ommochromes in the spider, a group of pigments that are of widespread occurrence in insects and some other arthropods (4). There is some debate whether the ommochromes actually act primarily as a protection against photodestruction by intense UV light (4), but the fact that M. vatia possesses the physiological ability to distinguish between certain colours in its environment (5) lends credence to them playing a role in mimicry.
Misumena vatia

  1. Ferriss et al. 2009, Irish Biodiversity: A Taxonomic Inventory of Fauna p. 38
  2. Sterry 2004, Collins Complete Guide to Irish Wildlife p. 152
  3. Gibbons, 1999. Collins Nature Guide Insects of Britain and Europe p. 229
  4. Théry and Casas, 2009. Philosophical Transactions of the Royal Society 364 pp. 471-480
  5. Defrize et al., 2011. Journal of Insect Physiology 57 pp. 508–513

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