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Aphidinae : Macrosiphini : Acyrthosiphon purshiae


Acyrthosiphon purshiae (= Macrosiphum purshiae)

Bitterbrush aphid

On this page: Identification & Distribution Other aphids on the same host

Identification & Distribution

Adult apterae of Acyrthosiphon purshiae (see first picture below) have the entire dorsum medium green, either slightly frosted or shining. Antennal segments I and III, the cauda and femora are pale brown, but all other parts of their appendages are black (cf. Acyrthosiphon malvae, which has mainly pale appendages). Their hairs are blunt; on the proximal half of antennal segment III they are 0.05 mm long. The apical rostral segment (RIV+V) is triangular, almost acute, hardly reaching the third pair of coxae, and less than 0.9 times the length of the second hind tarsal segment (HTII) (cf. Acyrthosiphon malvae, which has RIV+V more than 0.9 times HTII). The siphunculi are elongate, tapering, imbricated, not reticulated, and with a flange. The cauda is elongate, tapering, with scarcely any tendency to constriction at the base, and has three hairs on each side. The body length of adult Acyrthosiphon purshiae apterae is 2.0-2.5 mm.

Note: Acyrthosiphon purshiae was first described by Palmer (1938) in the genus Macrosiphum. Blackman suggests that that it should probably be returned to that genus given the DNA analysis by Foottit et al. (2008).

First image above copyright Andrew Jensen under a cc by-nc-sa licence;
Second image above copyright Walter Siegmund under a cc by-sa licence.

The alate Acyrthosiphon purshiae is presumably green, but we have found no description nor photo of the alate morph.

Acyrthosiphon purshiae is found on the leaves and stems of bitterbrush Purshia tridentata (see second picture above). Jensen noted that although bitterbrush is widespread and common in many dry habitats of the interior western North America, the aphid is not so common, only occurring in certain partially-forested areas where bitterbrush grows. The species is monoecious holocyclic, and is restricted to the western USA and British Columbia, Canada.


Other aphids on the same host

Blackman & Eastop list 2 species of aphid as feeding on bitterbrush (Purshia tridentata) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 1 as occurring in Britain (Show British list).


Identification was made by Andrew Jensen by microscopic examination of preserved specimens. We have used the keys and species accounts of Palmer (1938) & Palmer (1952) (both as Macrosiphum purshiae), together with information from Roger Blackman & Victor Eastop in Aphids on Worlds Plants. We fully acknowledge these authors and those listed in the reference sections 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


  • Foottit et al. (2008). Species identification of aphids (Insecta: Hemiptera: Aphididae) through DNA barcodes. Molecular Ecology Resources 8, 1189-1201. Full text

  • Palmer, M.A. (1938). Additional aphids from Colorado. Annals of the Entomological Society of America 31(3), 352-357. Abstract

  • Palmer, M.A. (1952). Aphids of the Rocky Mountain Region: including primarily Colorado and Utah, but also bordering area composed of southern Wyoming, southeastern Idaho and northern New Mexico. Thomas Say Foundation, Denver. Full text