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Aphidinae : Macrosiphini : Chaetosiphon thomasi
 

 

Chaetosiphon thomasi

American hairy rose aphid

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

Identification & Distribution

Adult apterae of Chaetosiphon thomasi (see first picture below) are pale yellowish green. Their antennal tubercles are rather well developed, whilst the median frontal tubercle is small, but conspicuous through the presence of two capitate hairs. The antennae are about as long as the body, and the terminal process is 3.8-4.9 times as long as the base of antennal segment VI. The apical rostral segment (RIV+V) is 0.06-0.08 times the body length (cf. Chaetosiphon fragaefolii on Potentilla, whose RIV+V is 0.08-0.11 times its body length). Abdominal tergites I-VII bear long and usually thick body hairs, with expanded or capitate apices, often much longer than the basal diameter of antennal segment III, and arising from prominent tuberculate bases. The dorsum is entirely pale with no pigmentation (cf. Chaetosiphon jacobi on Potentilla in western USA, which has a brown sclerotic dorsum). The first tarsal segments have 5 hairs. The siphunculi taper towards the distal half, curve inwards and slightly downwards, and have a very distinct flange; they are more than 2.5 times as long as the thick, blunt cauda (cf. Chaetosiphon tetrarhodum on rose, whose siphunculi are less than 2.5 times its caudal length). The body length of Chaetosiphon thomasi adult apterae is 1.0-2.6 mm.

Images above by permission, copyright Claude Pilon, all rights reserved.

Note: In the 1980s two Chaetosiphon species, Chaetosiphon fragaefolii and Chaetosiphon thomasi, were thought to occur sympatrically on strawberry, rose and Potentilla, only distinguishable from each other by the number of submarginal setae. Following a detailed study on variations in karyotype (=chromosome number), chaetotaxy (=bristle arrangement) and morphology (=body proportions), Blackman et al. (1987) assigned the name Chaetosiphon thomasi to a rose-feeding species holocyclic on Rosa rugosa in British Columbia (but with some records on Potentilla) - with Chaetosiphon fragaefolii occurring on strawberry and Potentilla. However, some American workers still seem inclined to synonomize Chaetosiphon fragaefolii (as Chaetosiphon fragariae?) with Chaetosiphon thomasi (see Jensen in AphidTrek). For example, AphID use an image of Chaetosiphon fragaefolii for Chaetosiphon thomasi (habitus).

Image above by permission, copyright Claude Pilon, all rights reserved.

The alate Chaetosiphon thomasi (image below) has a dark sclerotic head and thorax. The abdomen is membranous, with a dark inverted trapezoidal sclerotic patch from tergite III-V, and transverse bars on tergites VI-VII. The antennae of alatae are usually just longer than the body, blackish and bearing 20-37 rather large, slightly protruding secondary rhinaria on segment III, 2-4 rhinaria on segment IV and 0-1 rhinaria on segment V.

Image copyright Brendan Wray, AphID, USDA APHIS PPQ, Bugwood.org under a Creative Commons License.

Chaetosiphon thomasi is found on both wild and cultivated rose (Rosa) species and on some cinquefoil (Potentilla) species. Whether it feeds on silverweed (Potentilla anserina) is unclear - Blackman (Aphids on Worlds Plants) when describing the species, notes it does not feed on this host, but includes it in the listing for that plant. Chaetosiphon thomasi is found throughout North America, and has also been reported from Chile and Argentina.

 

Other aphids on the same host

Chaetosiphon thomasi has been recorded on 6 species of rose Rosa (Rosa acicularis, Rosa carolina, Rosa fendleri, Rosa foetida, Rosa gymnocarpa, Rosa rugosa).

Chaetosiphon thomasi has been recorded on 3 species of cinquefoil (Potentilla) (Potentilla gracilis, Potentilla norvegica, Potentilla pacifica).

 

Damage and control

Damage from Chaetosiphon thomasi to rose is similar to that caused by the related Chaetosiphon tetrarhodum.

Acknowledgements

We are especially grateful to Claude Pilon for pictures of Chaetosiphon thomasi (for more of her excellent pictures see).

Identification of specimens photographed by Claude Pilon was confirmed by Eric Maw by microscopic examination and DNA analysis of preserved specimens. For taxonomic details we have used the keys and species accounts of Hille Ris Lambers (1953) 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

References

  • Blackman R.L. et al. (1987). The strawberry aphid complex, Chaetosiphon (Pentatrichopus) spp. (Hemiptera: Aphididae): taxonomic significance of variations in karyotype, chaetotaxy and morphology. Bulletin of Entomological Research 77, 201-212. Full text

  • Hille Ris Lambers, D. (1953). Contributions to a monograph of the Aphididae of Europe. V. Temminkia 9, 1-176.