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Uroleucon taraxaciBronze-brown dandelion aphidOn this page: Identification & Distribution Biology & Ecology Other aphids on the same hostIdentification & DistributionAdult 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 (cf. Uroleucon sonchi which does not have dorsal abdominal hairs placed on dark scleroites). Antesiphuncular and post-siphuncular sclerites are either absent or very small (cf. Uroleucon hypochoeridis & Uroleucon cichorii which have crescent-shaped antesiphuncular sclerites present) 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.
The alate Uroleucon taraxaci (see second picture above) has large round dark marginal sclerites, but is otherwise coloured and marked similarly to the adult aptera. The clarified slide mounts below are of adult viviparous female Uroleucon taraxaci : wingless, and winged.
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 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:Life cycleUroleucon taraxaci overwinters as eggs laid on the old leaves of dandelion (Taraxacum officinale). The eggs hatch in spring, and colonies then grow in size over the summer. They are not usually noticed until late in summer because Uroleucon taraxaci is strongly photophobic, so colonies are located on the basal parts of the leaves of dandelions growing in shaded situations. A young colony 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.
Large colonies can build up by autumn.
Image above copyright Jochem Kuhnen, all rights reserved. In late autumn sexuales are produced. The oviparae (see pictures below of mating pairs) are dark reddish brown with slightly swollen hind tibiae bearing numerous scent glands.
Images above copyright Jochem Kuhnen, all rights reserved. The male Uroleucon taraxaci are usually described as small, slender and apterous (see first picture above). However, in the Netherlands one of our correspondents, Jochem Kuhnen, has also observed alate males (see second picture above) in the colony along with the normal apterous males. As far as we know, this is the first observation of a winged male of this species. A recently deposited egg can also be seen in the second picture (bottom right). Honeydew & Ant attendanceThe 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. Natural enemiesThere 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 (Bowers et al., 1972). Other aphids on same host:Uroleucon taraxaci has been recorded from 5 Taraxacum species (Taraxacum dens-leonis, Taraxacum kok-saghyz, Taraxacum officinale, Taraxacum serotinum, Taraxacum vulgare).
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