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Uroleucon taraxaci

Bronze-brown dandelion aphid

On this page: Identification & Distribution  Biology & Ecology  Other aphids on Common Dandelion 

Identification & Distribution:

Adult apterae of Uroleucon taraxaci are shining dark bronze-brown. The antennae and legs (except for the femoral bases) are black. Dorsal abdominal hairs are mostly placed on dark scleroites, which are black and numerous and sometimes merged together. Antesiphuncular and post-siphuncular sclerites are either absent or very small. The rather short and thick cauda is black like the siphunculi, and bears 8-12 hairs. The body length of the adult Uroleucon taraxaci aptera is 2.5-3.8 mm.

Micrographs of clarified mounts  by permission of Roger Blackman, copyright AWP  all rights reserved.

The bronze-brown dandelion aphid is seldom seen as, unlike most members of the genus, it is light-averse. It lives on leaf undersides and basal leaf parts of of dandelion (Taraxacum spp.) near ground level. Uroleucon taraxaci is found in Britain, throughout continental Europe, parts of Asia, and has been introduced to North America.

 

Biology & Ecology:

Uroleucon taraxaci is strongly photophobic. The two colonies we have found were located on the basal parts of the leaves of dandelions (Taraxacum officinale) growing in shaded situations. One of those colonies is shown below.

The youngest immatures are usually spaced out along the youngest leaves of the dandelion (as below).

The images below are of fourth instar immatures, the first being a future aptera and the second being a future alate.

 

The cauda of the fourth instar is short and triangular, but the adult (see picture below) has a short finger-like cauda.

The often partly-concealed location of the colony makes accumulation of honeydew droplets a potential problem because of bacterial growth. Some aphids flick honeydew away with their cauda (Blackman, 1974 ), but this would probably not be possible with such a short cauda. The problem is solved for many aphids by ant attendance, but Uroleucon aphids are not usually attended by ants (but see Tido (2002)  below). The bronze-brown dandelion aphid sometimes uses an alternative method to prevent accumulation of honeydew - it kicks the droplets away with its back legs. The aphid shown below has just kicked a droplet outside the frame of this picture.

van Emden (2013)  notes that many aphid species "kick honeydew droplets that form at the anus away from themselves to land elsewhere on the plant or fall to the ground." Tido (2002)  found a very large colony on the undersides of leaves and leaf bases of dandelion. Unlike the colony we found (and unusually for Uroleucon), it was attended by ants.

There is nothing in the literature about natural enemies of Uroleucon taraxaci, but the colony we observed (in captivity) was eventually eliminated by Aphidoletes larvae that hatched from eggs deposited prior to our finding this aphid colony. The first image below shows a yellowish Aphidoletes larva moving in for the kill, and the second shows the aphid nymph being held in the air by the midge larva shortly thereafter.

 

One noticeable aspect of the behaviour of the bronze-brown dandelion aphid is that the aphids drop off the plant at the slightest disturbance. Such predator escape mechanisms are quite common with aphids, often in response to release of the aphid alarm pheromone (E)-beta-farnesene (EBF) (Bowers et al., 1972 ).

 

Other aphids on Common Dandelion (Taraxacum officinale):

Blackman & Eastop list 37 species of aphid  as feeding on Taraxacum officinale worldwide, and provide formal identification keys. Of those aphid species, Baker (2015)  lists 25 as occurring in Britain: Aphis craccivora  Aphis fabae  Aphis gossypii  Aphis spiraecola, Aphis taraxacicola  Aulacorthum solani  Brachycaudus cardui  Brachycaudus helichrysi  Brachycaudus lateralis  Hyperomyzus lactucae  Hyperomyzus pallidus  Macrosiphum euphorbiae  Myzus ascalonicus  Myzus cymbalariae, Myzus ornatus  Myzus persicae  Neomyzus circumflexus  Pemphigus bursarius  Trama caudata, Trama rara,  Trama troglodytes  Uroleucon cichorii, Uroleucon grossum  Uroleucon sonchi  and Uroleucon taraxaci.

Acknowledgements

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

  •  Blackman, R. (1974). Aphids. Ginn, London.

  •  Bowers, W.S. et al. (1972). Aphid alarm pheromone: isolation, identification, synthesis. Science 177, 1121-1122.

  •  Tido, T. (2002). New records of aphids (Homoptera, Aphidodea) from Estonia. Proc. Estonian Acad. Sci. Biol. Ecol. 51(2), 124-137. Full text 

  •  van Emden, H.F. (2013). Handbok of Agricultural Entomology. Wiley-Blackwell. Abstract