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Aphidinae : Macrosiphini : Flabellomicrosiphum tridentatae


Flabellomicrosiphum tridentatae

Pale-legged frosted aphid

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

Identification & Distribution

Adult apterae of Flabellomicrosiphum tridentatae (see picture below) are pale green, 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 less than twice the length of the base of antennal segment VI (cf. Flabellomicrosiphum knowltoni, which has the terminal process more than twice the base of antennal segment VI). The rostrum reaches beyond the second pair of coxae, with the apical rostral segment (RIV+V) tapering, laterally compressed, and the tip beyond the hairs needlelike in ventral aspect. The dorsum bears numerous spatulate hairs. The legs including the femora (but not the tarsi) are pale (cf. Flabellomicrosiphum knowltoni, which has dark femora). The siphunculi are reduced to raised pores. The cauda is pale or dusky, and bears three pairs of lateral hairs. The body length of adult Flabellomicrosiphum tridentatae apterae is 0.9-1.5 mm.

Image above copyright Andrew Jensen under a creative commons licence.

The alate vivipara of Flabellomicrosiphum tridentatae (not pictured) is similarly colored to the aptera. The antennae are black-tipped shading to pale at the base, with segment III bearing 4-5 large flat secondary rhinaria. The legs are pale with the tips of the tibiae and tarsi black. The siphunculi are truncate or slightly mammiform, without a flange, and hardly more than a raised pore. The cauda is tapering to parallel-sided, elongate, and rather acute, with 3-4 hairs on each side and 2-3 dorsal ones near the tip.

Flabellomicrosiphum tridentatae is monoecious holocyclic on leaves and flower stems of big sagebrush (Seriphidium tridentata). Individuals are often found in rows, one behind the other on the leaves. Palmer (1952) describes this species as being rare. Jensen in Aphidtrek reports it to be locally common, but interestingly absent from large swaths of its host plant range; sagebrushes are known to be diverse in terms of plant chemistry, and it is possible that such variation in the plant controls the insect's distribution. The species is restricted to western USA.


Other aphids on the same host

Flabellomicrosiphum tridentatae has only been recorded on 1 Artemisia species (Artemisia tridentata).


We are grateful to Andrew Jensen for making his picture of Flabellomicrosiphum tridentatae available for use under a creative commons licence.

Identifications were made by the copyright holder of the picture. We have used the keys and species accounts of Wilson (1915) (as Chaitophorus tridentatae), 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


  • 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

  • Wilson, H.F. (1915). Miscellaneous aphid notes, chiefly from Oregon. Transactions of the American Entomological Society 41(2), 85-108. (p. 88,89). Full text