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Macrosiphum gaurae

Beeblossom aphid

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

Identification & Distribution

Adult apterae of Macrosiphum gaurae are variable in colour from green (see first picture below) to orange-red (see second picture below) to pink (see third picture below). Their antennae have segments I, II, and III light brown, segment IV dark brown, and the more distal segments dark brown to black (cf. Macrosiphum euphorbiae, whose antennae are mainly pale). The fused apical rostral segment (RIV+V) is 1.1-1.25 times as long as the second hind tarsal segment (HTII). Their legs are mostly light brown, but the tarsi and the distal parts of the femora and tibiae are dark brown to black. The siphunculi usually have the basal third pale and the distal two thirds dark brown to black (cf. Macrosiphum euphorbiae, which has mainly pale siphunculi with dusky tips). However, there is some evidence that the degree of darkening of the Macrosiphum gaurae siphunculi may vary across the continent (Jansen in Aphidtrek), if so the antennal coloration may be a more reliable discriminant from Macrosiphum euphorbiae. The cauda is dusky, but the same colour as the body (whether green or pink). The body length of adult Macrosiphum gaurae apterae is 2.7-3.9 mm.

Note: MacGillivray (1968) re-described twelve of the aphid species described as new by Edith M. Patch, including Macrosiphum gaurae, and synonomised Macrosiphum onagrae with Macrosiphum gaurae. Blackman notes that records of the very similar Macrosiphum pallidum from Onagraceae should probably all be referred to this species.

First two images above by permission, copyright Claude Pilon, all rights reserved
Third image above, Jesse Rorabaugh under a public domain licence.

Immature Macrosiphum gaurae (see first picture below) resemble the adult apterae, but with paler siphunculi and much shorter caudas. The alate Macrosiphum gaurae (see second and third pictures below) has a reddish brown head and thorax and a pale abdomen with the same abdominal colour variations as the apterae. The legs have the femora dark brown distally and paler basally, and the distal part of the tibiae and the tarsi dark brown to black. There are often light brown marginal sclerites on abdominal segments II-V. The siphunculi are dark distally but paler basally. The cauda is dusky and concolorous with the body.

First two images above by permission, copyright Claude Pilon, all rights reserved
Third image above, Jesse Rorabaugh under a public domain licence.

Macrosiphum gaurae feeds on the stems and leaves of beeblossoms (Gaurae spp.) and evening primroses (Oenothera spp.). They do not host alternate, but remain all year on Gaurae / Oenothera. Oviparae have been collected on Gaura in Oregon in October. The beeblosom aphid is widely distributed in he United States and Canada.

 

Other aphids on the same host

Acknowledgements

We are grateful to Claude Pilon for pictures of Macrosiphum gaurae (for more of her excellent pictures see and). And as always we thank Jesse Rorabaugh for the excellent images he provides under a public domain (cc0) licence.

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 We have used the keys and species accounts of Palmer (1952), and MacGillivray (1968) as well as Blackman & Eastop (1994) and Blackman & Eastop (2006) 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

  • MacGillivray, M.E. (1968). A review of twelve aphid species described as new by Edith M. Patch. Annals of the Entomological Society of America 61(2), 338-362. 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. Full text