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Black-backed coralbell aphidOn this page: Identification & Distribution Other aphids on the same host
Identification & Distribution
Adult apterae of Nasonovia davidsoni (see picture below - but check note) are reddish brown with a solid dark dorsal patch from the metanotum to abdominal tergite V, and rather dark antennae, legs, siphunculi and cauda. Antennae are 5 or 6 segmented, about 1.0-1.1 times the body length, and with a terminal process 6.0-7.0 times the base of antennal segment VI (cf. Nasonovia heucherae, which has the terminal process 4.8-6.9 times the base). Secondary rhinaria are distributed 32-37 on segment III, 11-14 on segment IV and 1-3 on V. The longest hair on antennal segment III is 1.0-1.1 times the basal diameter of the segment (cf. Nasonovia smithi, which has the longest hair on segment III 0.4-0.8 times basal diameter). The apical rostral segment is 2.0 times the second hind tarsal segment. There are marginal tubercles present on some tergites. Tarsal segment I has 3-3-3 hairs (fore,mid,hind). The siphunculi are 1.5-1.7 times the caudal length, cylindrical, and imbricated, with a well developed flange. The cauda is tongue-shaped, not constricted, with 5 hairs. Body length of adult Nasonovia davidsoni apterae is about 2.0-2.1 mm.
Note: The images below show a Nasanovia species on Heuchera in Belgium. It is most likely an American species brought in by the plant trade, namely Nasonovia davidsoni, Nasonovia heucherae or Nasonovia smithi, or possibly an undescribed species. The black dorsal patch suggests Nasonovia davidsoni or Nasonovia smithi, whilst the ratio of terminal process to base (5.3) for the aptera suggests Nasonovia heucherae.
Both images above, by permission copyright Dirk Baert, all rights reserved.
The alate Nasonovia davidsoni (see second picture above) is dark green, with brick-red ill-defined spots on the sides of abdomen. The abdomen has a large dusky dorsal patch, and dark marginal sclerites. The siphunculi are dark with paler apices, and cauda is rather pale. The antennae are about the same length as the body, with a terminal process 6.8-9.6 times the base of antennal segment VI. Secondary rhinaria are distributed 41 on antennal segment III, 17-20 on segment IV and 9-15 on segment V. The apical rostral segment is 1.8 times the second hind tarsal segment. Siphunculi are about 1.5 times the cauda, which is oblong triangular, and rather pointed. Young immatures (see picture below) are probably pale yellowish.
Image above, by permission copyright Dirk Baert, all rights reserved.
Nasonovia davidsoni is monoecious on the flowerstalks of Heuchera spp. in California, western USA. It is holocyclic, with an abbreviated life cycle, producing oviparae and alate males as early as May. Nasonovia heucherae and Nasanovia smithi also feed on Heuchera, but are found in USA east of the Rocky Mountains.
Other aphids on the same host
Blackman & Eastop list 3 species of aphid as feeding on small-flowered alumroot (Heuchera micrantha) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 1 as occurring in Britain (Show British list).