Adult apterae of Chaitophorus nigricentrus are broadly oval, dark yellow-brown to pinkish-brown to blackish-brown, with the central part of their dorsum darker than its margins (see first two pictures below). The base of antennal segment VI has 2-5 hairs, and the hairs on antennal segment III are mostly long and fine-pointed. The fused apical rostral segment (RIV+V) is 0.125 mm long and has 2-4 accessory hairs. The last two pairs of legs tend to be darker than the front legs. The hind femora are paler than the tergites, and the first tarsal segment (HTI) has 7 (rarely 6) hairs. The short, stump-shaped siphunculi are pale brown and reticulated. The cauda is broadly rounded with no trace of any constriction. The body length of adult Chaitophorus nigricentrus apterae is 1.5-1.8 mm.
Both images above by permission, copyright Claude Pilon, all rights reserved.
The dorsal cuticle is wholly or partly reticulated (see first picture below) (cf. Chaitophorus stevensis, which has no reticulate ornamentation, but has irregularly placed blunt nodules). The dark shapes in the abdomen of the specimen below are embryos.
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.
Alatae (not shown here) have dark dorsal abdominal cross-bands.
Chaitophorus nigricentrus lives in large colonies on the second-year growth of Salix species. The photos on this page show them feeding on the stems of dewy-stem willow (Salix irrorata). Judging from Claude Pilon's photographs (e.g. see second picture above) Chaitophorus nigricentrus is, at least sometimes, ant-attended. Little seems to be known about this species, but it probably produces sexuales in autumn. Chaitophorus nigricentrus has so far been recorded from Ontario & Montreal (these observations) in Canada, and from Pennsylvania in USA - but not outside America.
Other aphids on the same host
Previous records of Chaitophorus nigricentrus (Richards, 1972) only give "Salix" (ie. 1 or more, unidentified, willow species) as the host. We also list other aphids on dewy-stem willow (Salix irrorata) since that species hosted the Chaitophorus nigricentrus shown above.
Blackman & Eastop list 2 species of aphid (3, including Chaitophorus nigricentrus) as feeding on blue-stem willow (Salix irrorata) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 1 as occurring in Britain (Show British list).
Acknowledgements
We are especially grateful to Claude Pilon for pictures of Chaitophorus nigricentrus (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) 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).
Richards, W.R. (1972). The Chaitophorinae of Canada (Homoptera: Aphididae). The Memoirs of the Entomological Society of Canada104 Supplement S87, 1-109. Abstract
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