Host discrimination, i.e. the ability to distinguish unparasitized hosts from parasitized ones, and to reject the latter for egg laying is present in many parasitic wasp species. This property is classically considered as an example of contest competition, and is supposed to have a number of functions. However, different species do not react to each other's marks and lay eggs in hosts parasitized by the other species. Apparently the marks used for recognition are specific.
Bakker, K.; van Alphen, J.J. M.; van Batenburg, F.H. D.; van der Hoeven, N.; Nell, H. W.; and van Strien-van Liempt, W.T.F. H., "The function of host discrimination and superparasitization in parasitoids" (1985). An. Paper 270.
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