Aphid egg protection by ants: a novel aspect of the mutualism between the tree-feeding aphid Stomaphis hirukawai and its attendant ant Lasius productus
Aphids often form mutualistic associations with ants, in which the aphids provide the ants with honeydew and the ants defend the aphids from predators. In this paper, we report aphid egg protection by ants as a novel aspect of the deeply interdependent relationship between a tree-feeding aphid and its attendant ant. The ant Lasius productus harbours oviparous females, males, and eggs of the hinoki cypress-feeding aphid Stomaphis hirukawai in its nests in winter. We investigated the behaviour of ants kept with aphid eggs in petri dishes to examine whether the ants recognise the aphid eggs and tend them or only provide a refuge for the aphids. Workers carried almost all of the aphid eggs into the nest within 24 h. The ants indiscriminately tended aphid eggs collected from their own colonies and those from other ant colonies. The ants cleaned the eggs and piled them up in the nest, and egg tending by ants dramatically increased aphid egg survival rates. Starving the ants showed no significant effect on aphid egg survivorship. Without ants, aphid eggs were rapidly killed by fungi. These results suggested that grooming by the ants protected the aphid eggs, at least, against pathogenic fungi. This hygienic service afforded by the ants seems indispensable for egg survival of these aphids in an environment rich in potentially pathogenic microorganisms.
KeywordsAnt–aphid mutualism Symbiosis Myrmecophiles Egg protection
We thank Masato Sorin for providing helpful information about Stomaphis aphids and identifying the aphid species. We are also grateful to Sigeyuki Aoki for providing helpful information about aphids. This research complies with the current laws of Japan.
Video file (WMV 2,453 kb)
- Forbes (1906) The corn root-aphis and its attendant ant. (Aphis maidi-radicis Forbes and Lasius niger L., var. americanus Emery). Bull USDA Div Entomol 60:29–39Google Scholar
- Hölldobler B, Wilson EO (1990) The ants. Harvard University Press, Cambridge, MAGoogle Scholar
- Hölldobler B, Wilson EO (1994) Journey to the ants: a story of scientific exploration. Harvard University Press, Cambridge, MAGoogle Scholar
- Matsuura K (2003) Symbionts affecting termite behaviour. In: Miller TA, Bourtzis K (eds) Insect symbiosis. CRC Press, Boca Raton, FL, pp 131–143Google Scholar
- Pontin AJ (1960) Observations on the keeping of aphid eggs by ants of the genus Lasius (Hym., Formicidae). Entomol Mon Mag 96:198–199Google Scholar
- Sorin M (1995) Two new species and hitherto unknown sexual morphs of the genus Stomaphis Walker (Homoptera, Aphididae) from Japan. Bulletin of Kogakkan University 33:145–163Google Scholar