Flabellomicrosiphum knowltoni (Dark-legged frosted aphid) identification, images, ecology, control

Adult apterae of Flabellomicrosiphum knowltoni (see first picture below) are dull slate grey to pinkish or greenish, overlaid with numerous pale fan-shaped hairs giving it a frosted appearance. The antennae are more than half the length of the body. The terminal process is more than twice the length of the base of antennal segment VI (cf. Flabellomicrosiphum tridentatae, which has the terminal process less than twice the base of antennal segment VI). The rostrum reaches the third pair of coxae. The dorsum bears numerous spatulate hairs. The coxae, trochanters and femora are black and the hind tibiae are pale to dusky (cf. Flabellomicrosiphum tridentatae, which has pale femora). The siphunculi are reduced to raised pores. The cauda is dark, and bears two to three pairs of lateral hairs plus three to four dorsal or dorso-lateral hairs. The body length of adult Flabellomicrosiphum knowltoni apterae is 0.9-1.5 mm.

Flabellomicrosiphum knowltoni (dark-legged frosted aphid) on Artemisia tridentata (big sagebrush) in central Washington State, USA in April 2015; Andrew Jensen

First image above copyright Andrew Jensen, second image copyright Stan Shebs,
both under a creative commons licence.

The alate vivipara of Flabellomicrosiphum knowltoni is slightly darker than the aptera. The antennae are dusky, with segment III bearing 4 secondary rhinaria. The rostrum reaches beyond the second pair of coxae. The femora are dark, and the hind tibiae dusky. The siphunculi are merely raised pores.

Flabellomicrosiphum knowltoni is monoecious holocyclic on big sagebrush (Artemisia tridentata = Seriphidium tridentatum) (see second picture above). Oviparae have been found in Utah in October. Flabellomicrosiphum knowltoni are apparently very active when disturbed (see Jensen in aphidtrek). Like its foodplant, its distribution is restricted to western USA.

Other aphids on the same host

Blackman & Eastop list 43 species of aphid as feeding on big sagebrush (Artemisia tridentata) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 15 as occurring in Britain (Show British list).

Acknowledgements

We are grateful to Andrew Jensen for making his pictures of Flabellomicrosiphum knowltoni available for use under a creative commons licence.
Identifications were made by the copyright holder of the pictures. We have used the keys and species accounts of Smith (1937) and Palmer (1952), along 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

References

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
Smith, C.F. (1937). The aphid genus Flabellomicrosiphum in Utah. The Pan-Pacific Entomologist 13 (3), 127-129. Full text

Flabellomicrosiphum knowltoni

Dark-legged frosted aphid

Identification & Distribution

Other aphids on the same host

Acknowledgements

Useful weblinks

References