Abstract:
MANY insect parasitoids are capable of distinguishing whether their prospective hosts are healthy or whether the hosts already contain a parasitoid larva of the same or a different species. In many cases discrimination is made possible by an odour or chemical trace left on the surface of the host by the initial parasitoid1, or else gross. physical changes in the host such as desiccation or immobility2. Some endoparasitic ichneumonids can detect a parasitized host solely by penetration with the ovipositor 3-5, but nothing is known of the chemical stimuli, in the haemolymph which may elicit this discrimination.
