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Chaitophorus viminalis

Small black and green willow aphid

On this page: Identification & Distribution Biology & Ecology Other aphids on the same host Damage & Control

Identification & Distribution

The adult apterae of Chaitophorus viminalis are of variable colour in life, usually pale green to yellow in spring with darker green pleural stripes (see two pictures below). In summer they are often dark brown to black. (cf. Chaitophorus nigrae where the apterae are usually black, often with a paler spinal area; and cf. Chaitophorus pusillus where the apterae are whitish). The hairs on antennal segment III are very much longer on the inner side than on the outer side. The apical rostral segment (R IV+V) is short, less than 1.5 times its basal width and 0.6-0.8 times the length of the second hind tarsal segment (HTII). The first tarsal segments usually have 6-7 hairs (cf. Chaitophorus pusillus where the first tarsal segments mostly have 5 hairs). The siphunculi are pale, short and stump-shaped. The cauda is markedly knobbed with an almost globular or faintly elongated, small knob (cf. Chaitophorus nigrae where the cauda is very little knobbed, although sometimes there is a slight neck). The body length of adult apterae is 1.3-1.9 mm. Immatures are greenish-yellow, with the older nymphs having more prominent pleural stripes.

Hille Ris Lambers (1960) has noted that the species has often been misidentified in the literature, with some of those identified as Chaitophorus viminalis in fact being Chaitophorus stevensis, Chaitophorus populifolii or Chaitophorus nigrae.

First image above by permission, copyright Claude Pilon, all rights reserved.
Second image above copyright Whitney Cranshaw under a Creative Commons Attribution 3.0 license.

Alatae (not pictured) have dark dorsal abdominal cross-bands which often coalesce into a central patch.

The first picture below shows a clarified mount of a Chaitophorus viminalis adult aptera, whilst the second shows a colony attended by an ant.

First image above copyright Her Majesty the Queen in Right of Canada, Agriculture & Agri-Food Canada.
Second image above by permission, copyright Claude Pilon, all rights reserved.

Chaitophorus viminalis is found on leaves and young growth of various narrow-leafed willow species (e.g. Salix lucida & Salix nigra). Oviparae and alate males occur in October-November. They are frequently attended by ants (see pictures above & below). Chaitophorus viminalis is found throughout North America.

 

Biology & Ecology

Ant attendance

Nault et al. (1976) assessed the strength of the ant association for 11 species of aphids, including Chaitophorus viminalis and Chaitophorus populicola. When introduced to aphid colonies the chosen ant species, Formica subsericea, stroked with their antennae (or attempted to stroke) the bodies of all 11 species of aphids. However only 3 species of aphid (including both Chaitophorus species) responded to this 'antennation' by readily excreting honeydew droplets, and were classified as strongly myrmecophilous (weakly myrmecophilous species did not respond, non myrmecophilous aphids fled).

Image above copyright Judy Gallagher under a Creative Commons Attribution 2.0 license.

When attacked by predators, aphids secrete alarm pheromones from their siphunculi that normally cause nearby aphids to disperse and fall off their host. Nault et al. showed that the myrmecophilous aphid species (Chaitophorus viminalis, Chaitophorus populicola & Aphis fabae dispersed less readily than non-myrmecophilous species, and very few fell from the host. Instead they waggled their bodies, the function of which is not understood. When an ant was presented with aphid alarm pheromone (trans-beta-farnesene) on filter paper it ceased to antennate the aphids, extended its antennae forward, opened its mandibles and sometimes tried to bite the filter paper. These findings supported Nault et al.'s hypothesis that myrmecophilous aphids depend more on ants for protection from predators than on their own dispersive powers.

 

Other aphids on the same host

Chaitophorus viminalis has been recorded feeding on at least 7 willow species: white willow (Salix alba), weeping willow (Salix babylonica), sand dune willow (Salix cordata), sandbar willow (Salix exigua), shining willow (Salix lucida), black willow (Salix nigra) & osier (Salix viminalis).

Acknowledgements

We are especially grateful to Claude Pilon for pictures of Chaitophorus viminalis (for more of his 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) supplemented with Blackman (1974), Stroyan (1977), Stroyan (1984), Blackman & Eastop (1984), Heie (1980-1995), Dixon & Thieme (2007) and Blackman (2010). 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

  • Hille Ris Lambers, D. (1960). Some new genera and species of aphids from Canada. Canad. Ent. 92, 251-265. Abstract

  • Nault, L.R. et al. (1976). Ant-aphid association: role of aphid alarm pheromone. Science 192 (4246), 1349-1351. Full text

  • Richards, W.R. (1972). The Chaitophorinae of Canada. Mem. ent. Soc. Canada 87, 1-109. Abstract