XVIII.8.1 Some cases of warning coloring can fall under the extended phenotype category, i.e. they can be the product of genes located in the genome of species of organisms other than those that bear the warning colours
Morphological and physiological studies (Ishay & Shmuelson 1994)performed on wasps of the Vespa orientalis species have suggested that the yellow color of the warning stripes on the posteriors and the heads of the wasps is apparently caused by the hyphae of a certain kind of symbiotic fungus that are present in these stripes and simultaneously in wasp nests.Simultaneously, there is a difference in electrical potential between the yellow and brown stripes, probably caused by the fungus hyphae.This difference in potential could also be important in the morphogenesis of the wasp bodies in forming the parallel yellow stripes. The authors assume that certain types of symbiotic fungi are also responsible for the yellow stripes or spots on other kinds of hymenopterous insects.This, of course, points to the possibility that yellow stripes and thus the best known type of warning coloration could be “infectious” at a macroevolutionary level and could be transferred horizontally even between unrelated species of insects.The widespread nature of this warning coloration in eusocial hymenoptera could be related both to their eusociality, and thus easier transfer of fungi from one generation to the next between members of a single nest, and also to the fact that these are dangerous species of insects armed with stings and poison glands that are thus capable of bearing the load that is otherwise entailed in a brightly coloured phenotype (the emergence of a correlation between warning coloration and dangerousness or inedibility through species selection).
The advantage for the symbiotic fungus in its ability to induce bright yellow stripes on the body of insects remains a matter of speculation.Theoretically this could originally be one of the forms of manipulative activity of parasites transferred from one host to another by predation.As a consequence of the presence of brightly coloured stripes, the infected individual could readily become the prey of a predator, with simultaneous transfer of the parasite (fungus) to a new host.
In conclusion, it must be strongly emphasized that the mode of “infectious” warning coloration is interesting; nonetheless, there has been no independent confirmation of the presence and function of symbiotic fungi in the tissues of hymenopterous insects (however, it also seems that no one else has studied it).