Do oligosaccharides reduce the suitability of honeydew for predators and parasitoids?: A further facet to the function of insect-synthesized honeydew sugars

In summary, it can be said that honeydew from different sap feeders can vary considerably with respect to its carbohydrate composition. In addition, I have presented evidence that for parasitoids honeydew oligosaccharides are often less suitable as a source of food or kairomone in comparison to sucrose glucose and fructose. This reduced suitability can be due to their lower detectability, accessibility, and/or nutritional value. Overall, the available data lend support to the hypothesis that the synthesis of oligosaccharides by sap feeding insects could serve to reduce exploitation of honeydew by parasitoids and non-mutualist predators. This role does not exclude previously proposed functions. It is most likely that several selective forces have acted in concert to result in an evolutionarily optimal honeydew composition which may combine several functions. Melezitose and raffinose might represent such an optimal solution, as they combine a reduction in osmotic stress with both high attractivity to mutualist ants, and low acceptability and poor suitability to antagonists.