Plants mediate indirect ‘apparent’ effects between abovegroundherbivores and below-ground mutualistic mycorrhizalfungi. The herbivore–plant–mycorrhiza continuum is furthercomplicated because signals produced by plants in responseto herbivores can be transmitted to other plants via sharedfungal networks below ground. Insect herbivores, such asaphids, probably affect the functioning of mycorrhizal fungi bychanging the supply of recent photosynthate from plants tomycorrhizas, whereas there is evidence that mycorrhizas affectaphid fitness by changing plant signalling pathways, rather thanonly through improved nutrition. New knowledge of the transferof signals through fungal networks between plant speciesmeans we now need a better understanding of how thisprocess occurs in relation to the feeding preferences ofherbivores to shape plant community composition andherbivore behaviour in nature.