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Hoplochaitophorus quercicola

Spiny oakleaf aphid

On this page: Identification & Distribution Biology & Ecology Ant attendance Other aphids on the same host

Identification & Distribution

Adult apterae of Hoplochaitophorus quercicola (see first picture below) are greenish with complete or interrupted black abdominal cross bars on each segment. The antennal terminal process is more than 0.65 times the length of the base of antennal segment VI (cf. Hoplochaitophorus spiniferus, whose terminal process is less than 0.60 times the base of that segment). The longest hairs on antennal segment III are 1.0-1.25 times the basal diameter of that segment (cf. Hoplochaitophorus heterotrichus, which has the longest hairs on that segment long and fine, at least twice its basal diameter). The apical rostral segment (RIV+V) is shorter than the second hind tarsal segment (HTII). The pronotum has a group of marginal hairs on each side (cf. Hoplochaitophorus dicksoni, in which the pronotum only has one marginal hair on each side). Most dorsal body hairs are spine-like and are on tuberculate bases (cf. Hoplochaitophorus heterotrichus, in which spine-like dorsal hairs are outnumbered by fine hairs with finely-pointed apices - sometimes there are no spine-like hairs). The siphunculi are flared apically (cf. Hoplochaitophorus spiniferus, which has the siphunculi only slightly flared). The cauda is knobbed, and the anal plate is bi-lobed. The body length of adult Hoplochaitophorus quercicola apterae is 1.8-2.1 mm. Immatures (see second picture below) have less well developed dorsal markings, and tend to have some reddish-brown shading around the markings.

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

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.)

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