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Aphidinae : Macrosiphini : Uroleucon ambrosiae
 

 

Uroleucon ambrosiae

Brown ambrosia aphid

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

Identification & Distribution

Adult apterae of Uroleucon ambrosiae are red-brown to dark brown or dull red (see two pictures below), with black siphunculi and a pale cauda. The antennae are dusky to black, but paler on antennal segments I, II and the base of III, with 14-27 secondary rhinaria on segment III, and a terminal process which is 5.5-6.5 times the base of antennal segment VI (cf. Uroleucon leonardi, which has a terminal process 6.3-7.2 times the base of segment VI). The rostrum fully reaches the third pair of coxae, with the apical rostral segment (RIV+V) longer than the base of antennal segment VI. There are dusky scleroites on the dorsum of the abdomen. Abdominal marginal tubercles are absent (cf. Macrosiphum nigrotuberculatum, which has small black marginal abdominal tubercles). The hind tibia usually has a pale or dusky basal section, but this not as pale as the cauda for more than 0.5 of its length (Uroleucon ivae on Ambrosia & Iva, which has the tibia as pale as the cauda for more than 0.7 of its length). The second hind tarsal segment (HTII) is 0.9-1.1 times the length of RIV+V (cf. Uroleucon pseudoambrosiae, which has HTII 0.7-0.85 times RIV+V). The siphunculi are 1.1-1.3 times the length of the cauda, have a third of their length with polygonal reticulation, and are uniformly dark (cf. Uroleucon rudbeckiae, whose siphunculi are much paler at the base). The pale cauda tapers to a rather acute point, and bears 7-8 hairs on each side. The Uroleucon ambrosiae aptera body length is 2.5-3.5 mm.

Images above, copyright Jesse Rorabaugh, no rights reserved.

The Uroleucon ambrosiae alate vivipara is coloured similarly to the aptera, apart from having dark brown thoracic lobes and a dark blotch on tergite VI posterior to the base of each siphunculus. The antennae are entirely black, with 31-45 secondary rhinaria on antennal segment III. The rostrum hardly reaches the third pair of coxae. The dusky abdominal scleroites are often reduced or lacking.

The images below show clarified mounts of an apterous and an alate vivipara of Uroleucon ambrosiae.

Images of clarified mounts, above, copyright Brendan Wray under a Creative Commons License.

In eastern and northern USA, and Canada, Uroleucon ambrosiae is mainly found on Ambrosia and Iva. Moran 1985 felt that records from other plants were probably misidentifications of other species. However, populations in south-western USA, and Central and South America are far less specific, having been found feeding on the leaves and flower-stems of many additional genera in the Asteraceae including Achillea, Aster, Cichorium, Eupatorium, Lactuca, Rudbeckia and Senecio. The more polyphagous form is sometimes regarded in South America as a subspecies, Uroleucon ambrosiae ssp. lizerianum. The species is monoecious holocyclic in temperate North America with alate males, but it is usually anholocyclic in southern USA, and Central and South America.

 

Other aphids on the same host

Uroleucon ambrosiae has been recorded on 8 ragweed species (Ambrosia ambrosioides, Ambrosia artemisiifolia, Ambrosia confertiflora , Ambrosia deltoidea, Ambrosia paniculata, Ambrosia polystachia, Ambrosia psilostachya, Ambrosia trifida).

Uroleucon ambrosiae has been recorded on 3 sumpweed species (Iva cheiranthifolia, Iva oraria, Iva xanthifolia).

Uroleucon ambrosiae has been recorded on 1 species of Rudbeckia (Rudbeckia hirta)

Acknowledgements

We are grateful to Brendon Wray and Jesse Rorabaugh for making their pictures of Uroleucon ambrosiae available for use.

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 Palmer (1952) (as Macrosiphum ambrosiae) and Moran (1985), 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

  • Moran, N. (1985)[1984]. The Genus Uroleucon (Homoptera: Aphididae) in Michigan: Key, host records, biological notes, and descriptions of three new species. Journal of the Kansas Entomological Society 57(4), 596-616. Full text

  • 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