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Uroleucon tanaceti

Crimson tansy aphid

Identification & Distribution  Biology & Ecology 

Identification & Distribution:

Apterae of Uroleucon tanaceti are red, reddish brown or crimson, with yellowish antennae and black apices. The legs are (usually) yellow with the apices of the tibiae black. The siphunculi are brown or black, often with the middle part paler brown giving a characteristic bicoloured appearance. The cauda is yellow. The body length of Uroleucon tanaceti is 2.2 to 3.4 mm.

Guest images copyright Nigel Gilligan, all rights reserved

Antesiphuncular and marginal sclerites are absent. Body hairs are long and placed on small, discrete scleroites.

The crimson tansy aphid is found on tansy (Tanacetum spp.), especially on the lower yellowing leaves. It also occurs on cultivated Chrysanthemum species. Winged males and wingless female oviparae occur in October. Uroleucon tanaceti is distributed throughout Europe to Siberia and Central Asia, and North America.

 

Biology & Ecology:

We have never found Uroleucon tanaceti ourselves, but Nigel Gilligan (one of our regular contributors from the north of England) sent us these photos in 2014. Its brick red colouration appears to be an example of aposematic colouration,  warning intentional predators (such as birds) and unintentional predators (such as herbivores) that the insect is distasteful or otherwise nasty. A closely related aphid, Uroleucon nigrotubeculatum, gets it brick-red colouration from a quinone pigment named uroleuconaphin (Horikawa et al., 2006 ). We suspect that Uroleucon tanaceti uses the same, or a very similar, pigment.

Tansy, also known as cow bitter or bitter buttons, contains a volatile oil containing thujone, camphor and myrtenol, which give tansy its bitter taste to vertebrates. If consumed in large quantities the leaves and flowers are toxic to humans. The crimson tansy aphid is also unpalatable to invertebrate predators, namely Coccinella septempunctata and Chrysopa carnea. Mehrparvar et al. (2013)  found that the larvae of neither of these predators could reach maturity when reared only on the crimson tansy aphid. When offered a mixture of these and more palatable tansy aphids such as Metopeurum fuscoviride  and Macrosiphoniella tanacetaria they could mature but fitness parameters were still lower than for aphids feeding only on a palatable host. Surprisingly it seems that the predators were unable to avoid feeding on the unsuitable (toxic?) aphid species.

Aposematically coloured insects normally display their colour as much as possible, and sure enough when Nigel first spotted the aphids many of them were spaced out in a near regular pattern of dispersion on the upper surface of the leaves (see picture below).

Guest image copyright Nigel Gilligan, all rights reserved

But Mehrparvar et al. (2013)  and other workers have reported that Uroleucon tanaceti lives hidden on the undersides of the lower leaves. Heie, 2009  points out that living in a concealed position is not one would expect from an insect displaying aposematic colouration, and describes it as an 'aphid mystery'.

Further examination of the plants by Nigel revealed that those up top were the adults and most of the colony (including all the young) were on the undersides of the leaves (see first picture below). It seems plausable that adults on the top of the leaves are 'sacrificial lambs' which predators might take (and then regret), thus ensuring that the great majority of the colony remained untouched. Possibly adults on top of the leaf were post-reproductive, although this would not be required to explain such behaviour given that all individuals in the colony were likely to be closely related.

 

Guest images copyright Nigel Gilligan, all rights reserved

So why have some workers not found any on the upper surfaces? Well, on a repeat visit to the colony following some wet weather, Nigel found that found that all the aphids were on the undersides of the leaves. So do they move to the undersides of the leaves for shelter during rain? We suggested a simple experiment of spraying the aphids with water - and sure enough a light sprinkle of water on the aphids produced a rush for cover (see second picture above). Rain is acknowledged as an important factor responsible for aphid mortality (Wellings & Dixon, 1987 ), so it makes sense for vulnerable aphids to shelter on the leaf underside in wet weather. It seems their display is very dependent on environmental conditions - which at least may explain why other workers have not noticed it.

There is some evidence that Uroleucon tanaceti can manipulate plants' nutritional quality to make it more palatable (to them, that is). Infestation with this aphid increases the percentage of methionine plus tryptophan in the phloem tenfold, which causes premature leaf senescence hence improving its nutritional quality for the aphid (Nowak & Komor, 2010 ).

Acknowledgements

Our sincere thanks to Nigel Gilligan for the pictures shown above.

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 Blackman & Eastop (1994)  and Blackman & Eastop (2006)  supplemented with Blackman (1974) , Stroyan (1977) , Stroyan (1984) , Blackman & Eastop (1984) , Heie (1980-1995) , Dixon & Thieme (2007)  and Blackman (2010) . 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

  •  Heie, O.E. (2009). Aphid mysteries not yet solved/Hemiptera:Aphidomorpha. Aphids and other hemipterous insects 15, 31-48. Full text 

  •  Nowak, H. & Komor, E. (2010). How aphids decide what is good for them: experiments to test aphid feeding behaviour on Tanacetum vulgare (L.) using different nitrogen regimes. Oecologia 163 (4), 973-984. Behavioural Processes 40(1), 75-83. Abstract 

  •  Mehrparvar, M. et al. (2013). Diet-mediated effects of specialized tansy aphids on survival and development of their predators: Is there any benefit of dietary mixing? Biological Control 65, 142-146. Full text 

  •  Wellings, P.W. & Dixon, A.F.G. (1987). The role of weather and natural enemies in determining aphid outbreaks. pp. 314-340 in: Barbosa, P. & Schultz, J.C. (ed.) Insect Outbreaks. Academic Press.

 

Identification requests

Nigel Gilligan, 30 September 2014

I have actually today just taken some shots (still the old camera) of some aphids I spotted on some Tansy. I looked up tansy aphid, and it doesn't seem to fit the bill, from shape or colour, which was a tad darker than pillar-box red. I did look up what else might use Tansy, and couldn't spot anything amongst the likely candidates. Never seen such striking little beasts before, and the shots look great! I shall hope to progress it in the next day or so, but if I can't find it, I may have to ask for some more help.

Nigel Gilligan, 1 October 2014

As I mentioned, I have been looking at this red aphid, and being puzzled, and impressed by its bright appearance.

It has some similarity to the overall forms in the Uroleucon genus, from what I can see on the influential points page. But it doesn't actually match any of those I can see, differing in quite a few details to all of them (I think).

It is the right sort of plant area - mine was on a common tansy - Tanacetum vulgare.

I've attached two images, which show the various parts sufficiently, but probably not the minute detail required for a Dogwood aphid!

 

Any use?

Bob, Influentialpoints:

  • Your large daisy aphid is Uroleucon tanaceti - not one we have seen before.

    Fortunately it is very distinctive with the bright red body colour, pale yellow cauda, and siphunculi which are pale in the middle but dark at the tips and base.

    We shall look forward to putting it on the website with your piccies, assuming that is OK with you.