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Identification & Distribution

Adult apterae of Chaitophorus nudus are broadly oval in shape, and are coloured dark brown to shiny black (see first picture below). Their antennae and legs are wholly dark. The longest hairs on antennal segment III are 1.5 times as long as the basal diameter of segment III. Abdominal tergites II-VII are wholly sclerotized and fused into a solid tergum (=dorsal part of the segment). The fused apical rostral segment (RIV+V) is 0.2 mm long, and has 2-4 accessory hairs. Tergites II-VII each have 3-5 spinal hairs and some marginal hairs, but they have no pleural hairs (cf. both Chaitophorus populicola and Chaitophorus nodulosus, where tergites II-VII have spinal, marginal and pleural hairs). The short, somewhat truncate siphunculi are pale or a little dusky. The cauda is rounded without any trace of constriction. The body length of adult apterae is 2.0-2.6 mm. Immature Chaitophorus nudus are greyish-brown.

Note: More information on Chaitophorus nudus is given in Richards (1972).

All three images above by permission, copyright Claude Pilon, all rights reserved.

Chaitophorus nudus alatae have the dorsal abdomen blackish or dark green with black bars or cross-bands (see second picture above). The dark forewing veins are broadly grey bordered, with a more-or-less conspicuous black pterostigmal spot (see third picture above). There are 11-27 secondary rhinaria on antennal segment III, 2-8 on segment IV, 0-2 on segment V, and none on antennal segment VI.

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

Chaitophorus nudus is found usually in rather small colonies on the trunk of saplings (and possibly branches of more mature trees) of quaking aspen (Populus tremuloides) (cf. Chaitophorus populicola, which is only found on the young shoots, developing leaves and leaf petioles of poplars, Populus spp.). Sexuales (large pale oviparae and alate males) develop in autumn. Poplar stem aphids are often attended by ants (see picture above). Chaitophorus nudus is found in southern Canada (Manitoba, Ontario, Quebec) and western and northern USA (Colorado, Pennsylvania).

 

Biology & Ecology

Natural enemies

Batulla & Robinson (1960) recorded several hymenopterous parasitoid species parasitizing Chaitophorus nudus on Populus tremuloides, including Ephedrus incompletus and Praon artemisaphis. There was also an unidentified Praon species and an unidentified Trioxys species.

 

Other aphids on the same host

Blackman & Eastop list 19 species of aphid as feeding on quaking aspen (Populus tremuloides) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 1 as occurring in Britain (Show British list).

 

Damage and control

Quaking aspens (Populus tremuloides) are sometimes planted as garden trees (but beware, they can be invasive as they grow quickly from seed and suckers). Large populations of poplar stem aphids may cause problems with deposition of honeydew with consequent sooty mould on the tree, but natural enemies usually control aphid populations before there is any damage to the tree.

Acknowledgements

We are especially grateful to Claude Pilon for pictures of Chaitophorus nudus (for more of her excellent pictures see, and).

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

  • Batulla, B.A. & Robinson, A.C. (1984). Hymenopterous parasites of aphids (Homoptera: Aphididae) in Manitoba. Proc Entomol Soc Manitoba 40, 30-38. Full text

  • Richards, W.R. (1972). The Chaitophorinae of Canada (Homoptera: Aphididae). The Memoirs of the Entomological Society of Canada 104 Supplement S87, 1-109. Abstract