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Goldenrod aphidOn this page: Identification & Distribution Biology & Ecology Life cycle Colour Natural enemies Other aphids on the same host
Identification & Distribution:
Uroleucon solidaginis apterae are shining reddish brown, with rows of dark hair-bearing scleroites. The antennae and legs of Uroleucon solidaginis are mainly yellowish brown with the apical parts of the femora, knees and tips of tibiae dark. Their antennae are longer than the body and the third antennal segment is as dark as the rest of the antennae. The antennal terminal process is 5.2-6.4 times the length of the base of antennal segment VI. The apical rostral segment is 1.2-1.4 times the length of the second hind tarsal segment, and bears 8 accessory hairs. There are no antesiphuncular sclerites. Both the siphunculi and cauda are black, and their siphunculi are 1.6-2.1 times as long as the cauda. The distal 25% of the siphunculi is reticulated. Uroleucon solidaginis body length ranges from 2.3 to 4.1 mm.
The alate viviparous female is dark red, and has completely black antennae about 1.3 times as long as the body. Immatures are bright red. The alate male is dark green, and the ovipara has the hind tibia swollen with 12-25 secondary rhinaria on antennal segment III.
The clarified slide mounts below are of adult viviparous female Uroleucon solidaginis : wingless, and winged.
The goldenrod aphid is found on the upper parts of goldenrod (Solidago virgaurea). It does not host alternate, but produces oviparae and green alate males in the autumn. They overwinter in the egg stage. Uroleucon solidaginis is found in Europe, Asia, north Africa and North America.
Biology & Ecology
We have so found the aphid Uroleucon solidaginis at two sites in Britain - at Dundreggan in Scotland and at Bedgebury Pinetum in Kent. We first found it at Dundreggan in July on a small patch of golden rod. There was only one live aphid in the colony (a fourth instar nymph) and this was reared through to the adult for identification purposes (see pictures below). Most of the colony had been parasitized.
Bedgebury Pinetum provided some much larger colonies (see pictures below) again in July on the abundant golden rod growing alongside tracks through the pinetum. There were numerous adult apterae with immatures, but no alatae - a surprising absence since they were quite high density colonies on the stems and Uroleucon normally produce their dispersive alatae in mid-summer.
Green alate males start to be produced from July onwards, and these mate with the oviparae which lay the overwintering eggs on the old plant stems and leaves.
The first thing one notices about Uroleucon solidaginis is its crimson red colouration, reminiscent of the coloration of several other aphid species (e.g. Uroleucon tanaceti and Uroleucon picridis) which feed in exposed situations liable to attract the attention of bird predators.
This is most likely aposematic colouration for defensive purposes (Prudic et al., 2006) directed at bird predators. This could be Batesian mimicry (where the aphid is edible, but is mimicking an insect that is distasteful), or it could be Mullerian mimicry (where the aphid is inedible, and is using a common warning colouration pattern).
There is some information available on the likely toxicity, or otherwise, of Solidago species. Worthley et al. (1967) assessed the toxicity of 8 species of Solidago. Five of them, including Solidago canadensis), a known host of Uroleucon solidaginis contain alkaloids. However, there are not thought to be any active toxins in Solidago virgaurea (European goldenrod, European Medicines Agency, 2008).
The alate males of Uroleucon solidaginis are coloured quite differently - they are a pale yellowish green, which is most likely cryptic coloration matching the background colour of the plant stem (see picture of colony of Uroleucon solidaginis with males by Jarmo Holopainen).
The colony we found in Dundreggan had been parasitized, so the plant was covered with large numbers of golden brown mummies.
All primary parasitoids had already emerged, so we cannot make a positive identification of the parasitoids. The most commonly recorded species attacking Uroleucon solidaginis are Aphidius funebris (Tomanovic et al, 2003) and Ephedrus persicae (Tomanovic et al, 2009).
Two species of hyperparasitoid (parasitoid of the primary parasite) were reared from two Uroleucon solidaginis mummies. They were identified as Alloxysta arcuata and Phaenoglyphis villosa.
The hyperparasitoid Phaenoglyphis villosa is pictured above.
As for predators, one likely candidate was the mirid bug Plagiognathus arbustorum found amongst the Uroleucon solidaginis colonies at Bedgebury Pinetum. This is a generalist aphid predator known to be both a predator of small insects and a plant feeder, especially on nettles (Urtica dioica).
Several species of spiders added to the number of polyphagous predators preying on the goldenrod aphid population.
In addition there were eggs of a predatory midge (Cecidomyiidae) laid on some of the adult apterae - in the image below, neatly between its siphunculae.
Other aphids on same host:
Uroleucon solidaginis has been recorded on 3 Solidago species (Solidago canadensis, Solidago decurrens, Solidago virgaurea).