Hoplochaitophorus quercicola

Identification & Distribution

Hoplochaitophorus quercicola alatae have dusky forewings with dark-bordered veins.

Hoplochaitophorus quercicola is found on several oak (Quercus) spp. especially white oak (Quercus alba), bur oak (Quercus macrocarpa) and chestnut oak (Quercus prinus). They live in dense colonies along the leaf veins, both on the leaf undersides (Monell 1879) and uppersides (Granovsky, 1933). Oviparae with long, drawn-out ovipositors, and apterous males develop in autumn. The spiny oak leaf aphid is found in the United States (except the north-west) and Canada.

Biology & Ecology

Ant attendance

The relationship of Hoplochaitophorus quercicola with ants is unclear. Some genera in the same sub-family (Calaphidini) are strongly ant-attended (e.g. Symydobius), whilst others are rarely if ever ant-attended (e.g. Euceraphis). Pilon (pers. comm.) observed ants (Lasius sp.) ascending an oaktree and descending carrying Hoplochaitophorus quercicola presumably for consumption in their nest. During an hour of observation, at least twenty ants were observed carrying live aphids.

Image above by permission, copyright Claude Pilon, all rights reserved.

So why were the ants not exploiting the aphids for honeydew, but instead (apparently) predating them? Mutualism provides the ants with a consistent source of carbohydrate in the form of honeydew. Predation, on the other hand, provides the ants with protein. It could be that the ants' diet was deficient in protein at this site. and at the time of the observations this deficiency led to the observed predation. It is quite possible that at other times the ants attend the aphids for their honeydew, as switching between predation and mutualism has been documented in other ant-aphid interactions (Pontin, 1958; Way, 1963).

Image above by permission, copyright Claude Pilon, all rights reserved.

Other aphids on the same host

Hoplochaitophorus quercicola has been found on 6 species of Quercus (Quercus alba, Quercus macrocarpa, Quercus prinus, Quercus stellata, Quercus velutina.)

• Blackman & Eastop list 12 species of aphid as feeding on bur oak (Quercus macrocarpa) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists none occurring in Britain (Show British list).

• Blackman & Eastop list 11 species of aphid as feeding on chestnut oak (Quercus prinus) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists none occurring in Britain (Show British list).

Acknowledgements We are grateful to Claude Pilon for pictures of Hoplochaitophorus quercicola in Canada (for more of her excellent pictures see). We have made provisional identifications from high resolution photos of living specimens, along with host plant identity. In the great majority of cases, identifications have been confirmed by microscopic examination of preserved specimens. We have used the keys and species accounts of Blackman & Eastop (1994) and Blackman & Eastop (2006). We fully acknowledge these authors as the source for the (summarized) taxonomic information we have presented. Any errors in identification or information are ours alone, and we would be very grateful for any corrections. For assistance on the terms used for aphid morphology we suggest the figure provided by Blackman & Eastop (2006).

Useful weblinks

References Granovsky, A.A. (1933). Two new genera and species of Aphiidae (Homoptera). Proceedings of the Entomological Society of Washington 35 (3), 29-43. Full text Monell, J. (1879). Notes on the Aphididae with descriptions of new species. Bulletin of the United States Geological and Geographical Survey of the Territories 5(1), 18-32. Full text Pontin, A. J. (1958). A preliminary note on the eating of aphids by ants of the genus Lasius. Entomologists Monthly Magazine 94, 9-11. Way, M. J. (1963). Mutualism between ants and honeydew-producing Homoptera. Annual Review of Entomology, 8, 307-344. Abstract