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Chaitophorus stevensis

Speckled poplar aphid, Green aspen aphid

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

Identification & Distribution

Adult apterae of Chaitophorus stevensis are pale green with dark green (see first picture below) or dark reddish-brown (see second picture below) markings on the abdomen (note that these darker markings are unsclerotized, and are not visible in clarified slide mounts). Their antennae are mainly pale, although sometimes the apex of the base of segment IV and the apex of the terminal process are darkened. The longest hairs on antennal segment III are mostly less than twice as long as basal diameter of that segment. The fused apical rostral segment is 0.075-0.100 mm long, with 1-3 secondary hairs. Abdominal tergite I is frequently fused with abdominal tergites II-VI. Dorsal ornamentation consists of rather evenly-distributed separate roundish nodules. The hairs of abdominal tergites I-VIII are very variable in size and form; they are arranged on each tergite more-or-less in a single row (cf. Chaitophorus neglectus and Chaitophorus populifolii, in which hairs on each tergite are arranged in two irregular rows). Abdominal tergite VIII has 7-12 hairs (cf. Chaitophorus neglectus and Chaitophorus populifolii, in which tergite VIII usually has more than 12 hairs). The siphunculi are pale, short, and truncate . The cauda is knobbed, and is clearly visible in the adult apterae in the first two pictures below (the aphid with the purplish-red markings in the second picture is quite large, but is still a fourth instar nymph so the cauda is not yet fully developed). The body length of adult apterae is 1.6-2.0 mm. Immature Chaitophorus stevensis are pale green or reddish-brown, with or without darker markings.

Note: Richards (1972) covers this species under the synonym Chaitophorus delicatus.

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

Chaitophorus stevensis alatae have 8-15 secondary rhinaria on antennal segment III (which are scattered, not in a row), there are 0-5 on antennal segment IV, and 0-1 on segment V. The sclerotized bars on abdominal tergites III-VI are much wider than those on tergites I and II (see second picture below). Thes bars are often more-or-less fused to form a central dorsal patch. The siphunculi of alatae are dark.

First image above copyright CBG Photography Group under a Creative Commons Zero (CC0) license.
Second image above, by permission, copyright Claude Pilon, all rights reserved.

Chaitophorus stevensis feeds on cottonwoods (mainly Populus deltoides and Populus angustifolia) and aspens (Populus grandidentata and Populus tremuloides). It is usually attended by ants (cf. Chaitophorus neglectus which is not ant attended). Blackman indicates it is frequently associated with leaf-fold galls of another aphid, Thecabius populiconduplifolius. Chaitophorus stevensis is found throughout North America, but not elsewhere.

 

Biology & Ecology

While the effects of global atmospheric changes (specifically CO2 & O3) on vegetation and the resulting impact upon insect populations are being increasingly studied, it is less clear how these gases modify interactions among insects and their natural enemies. As natural enemy efficacy is governed largely by behavioural mechanisms, altered prey finding and prey defence may change insect population dynamics. Mondor et al. (2004) looked at how pheromone-mediated escape behaviours, and hence the vulnerability of insects to natural enemies, varied under atmospheric conditions associated with global climate change. Chaitophorus stevensis, a common aphid on trembling aspen trees, Populus tremuloides, disperse less in response to alarm pheromone in enriched carbon dioxide environments, while those in enriched ozone environments disperse more in response to alarm pheromone. Mondor et al. concluded such divergent pheromone-mediated behaviours could alter predator-prey interactions in future environments.

 

Other aphids on the same host

Chaitophorus stevensis has been recorded on 5 species of poplar (Populus) (Populus angustifolia, Populus deltoides ssp. deltoides, Populus deltoides var occidentalis, Populus grandidentata, Populus tremuloides).

Blackman & Eastop list 25 species of aphid as feeding on Eastern cottonwood (Populus deltoides ssp. deltoides) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 3 as occurring in Britain (Show British list).

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

Wilson (1976) considered the speckled poplar aphid (Chaitophorus stevensis) a significant, injurious, sapsucking pest of intensively-grown Populus. He noted these aphids feed on expanding leaves, especially on sucker shoots, and cause them to curl upward.

Acknowledgements

We are especially grateful to Claude Pilon for pictures of Chaitophorus stevensis (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

  • Mondor, E.B. et al. (2004). Divergent pheromone-mediated insect behaviour under global atmospheric change. Global Change Biology 10, 1820-1824. 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

  • Wilson, L.F. (1976). Entomological problems of forest crops grown under intensive culture. 50(3), 277-286. Full text