A study by Spanish scientists has revealed that paper wasps, Polistes dominula, advertize the size of their poison glands to potential predators.
Paper wasps in a can (Vidal-Cordero et al / Frontiers in Zoology)
The theory of aposematism, or warning signals, describes the phenomenon that prey may use conspicuous signals to warn predators about their unprofitability. Usually this takes the form of distinctive coloration or patterns which predators quickly learn to avoid.
Paper wasps are known to have conspicuous yellow and black patterns covering their bodies that make them clearly recognizable and warn predators away.
In the new study, researchers from University of Granada and the University of Almeria have found a direct relationship between the size of a wasp’s poison gland and the brightness of its color.
“It might be thought that bigger wasps have bigger poison glands, and this is indeed true, but even when the data have been adjusted to take into account the size of the insect, a positive correlation between gland size and brightness remained,” explained Dr Gregorio Moreno-Rueda, who led the study published in the journal Frontiers in Zoology.
But producing both the poison and the distinctive coloration is costly to the wasp. To get around this problem, some species, such as hoverflies, have learnt to mimic poisonous ones. But other animals use coloration as a truthful signal.
In this case, the wasp would be signaling that it is so strong and healthy that it can waste energy producing bright color; and a strong and healthy wasp will contain a lot of poison.
“A second possibility is that the pigment is also an antioxidant that helps protect the insect from its own poison or from the by-products of poison production,” Dr Moreno-Rueda said. “Consequently an insect which has a lot of poison will also have a lot of color.”
“Either way predators need to beware – a bright wasp will leave a nasty taste in the mouth.”
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Bibliographic information: Vidal-Cordero et al. 2012. Brighter-colored paper wasps (Polistes dominula) have larger poison glands. Frontiers in Zoology, 9:20; doi: 10.1186/1742-9994-9-20
