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Genus Uroleucon [Macrosiphini]

The apterae are medium-sized to rather large aphids which may be shiny red, reddish brown or blackish brown. The antennal tubercles are well developed, smooth with diverging sides. The antennae are about as long as the body. Dorsal abdominal hairs are not capitate and are placed on scleroites which are normally dark. Antesiphuncular sclerites may be present or absent; postsiphuncular scleroites are normally present. The siphunculi are black and long with a zone of polygonal reticulation occupying the subapical 0.15-0.4 of their length. The cauda is yellow, dusky or black, finger shaped, long and rather pointed.

This is a large genus with 226 species distributed worldwide associated almost entirely with the daisy (Asteraceae) and bellflower (Campanulaceae) families. They either feed on, only one species, or only a few related species. They do not host alternate. They usually have a sexual stage in their life cycle and overwinter as eggs. They are not usually attended by ants.

 

Uroleucon achilleae (Red yarrow aphid)

Apterae of Uroleucon achilleae are red or brownish red with rows of black dorsal spots. Their antennae are pale with darker segments I, II and the tips of segments of the flagellum. The legs are yellow with the apical one third of femora and the bases and tips of tibiae black. Marginal sclerites and antesiphuncular sclerites are absent. Abdominal hairs are long and placed on rather large scleroites. The siphunculi are black, and cauda is yellow. The body length of Uroleucon achilleae is 2.4-2.6 mm.

The alate is similar to the apterous adult, but has marginal and antesiphuncular sclerites and cross bars on abdominal segments VII and VIII. The ovipara has the basal half of the hind tibia dark and swollen.

Uroleucon achilleae feeds on the lower leaves of yarrow (Achillea spp.) where it can cause withering. It does not host alternate. Oviparae and alate males occur in October (sometimes earlier). It is found throughout most of Europe and has been introduced to California and Oregon in the USA.

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Uroleucon aeneum (Dark-tailed thistle aphid)

Uroleucon aeneum Apterae are shiny metallic bronze-black. The third antennal segment has rhinaria extending over 0.37-0.52 of the length. The tibiae have a paler middle section, and the hind femur is dark on the distal 0.4-0.5. Uroleucon aeneum siphunculi have reticulation on the distal 0.15-0.20, and the cauda is wholly dark (compare to the yellow cauda of Uroleucon cirsii ). The body length of apterae is 3.0-4.3 mm.

Guest image copyright Alan Outen, all rights reserved

Uroleucon aeneum lives in sometimes very large colonies on the upper parts of stems of thistles, mainly Carduus and Cirsium spp. The dark-tailed thistle aphid does not host alternate but remains all year round on thistle. Oviparae and alate males appear in September. Uroleucon aeneum is found throughout Europe to Turkey, Armenia, Kazakhstan and Siberia, and has been introduced to Argentina and Chile.

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Uroleucon campanulae (Harebell aphid)

These aphids are shiny reddish brown to black. Their body hairs are thick and placed upon well developed scleroites. The antesiphuncular sclerites are little developed in apterae but usually well developed in alates. The antennae, siphunculi, and cauda are black and the legs are bicoloured yellow and black. The body length of is 2.1 to 3.7 mm. The siphunculi have polygonal reticulation over more than 0.2 of their length. The siphunculi are 0.85-1.25 times the length of the cauda. The fused 4th and 5th rostral segment is 0.8-1.05 times the length of the second hind tarsal segment. Populations from different regions and hosts differ somewhat in morphology and there is possibly a complex of species in Europe.

This aphid feeds on the upper parts of stems and flowers of Campanulaceae (Harebells) especially Campanula rotundifolia, Campanula rapunculus and Jasione montana, in Europe and Central Asia.

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Uroleucon cichorii (Large chicory aphid)

Adult apterae of Uroleucon cichorii are shining metallic grey-brown with black antennae and siphunculi. The femora are yellow basally and black on the distal half. The key distinguishing characer is that the Uroleucon cichorii tibiae are entirely black (cf. Uroleucon grossum  and Uroleucon obscurum  which have much of the basal half of the tibiae yellow-brown rather than black). The apical segment of the rostrum is 1.04-1.33 times the length of the second hind tarsal segment.The antennal terminal process is 5.4-8.4 times longer than the base of antennal segment 6. The siphunculi are 1.1-1.7 (normally 1.4-1.6) times the length of the cauda. The body length of the adult Uroleucon cichorii aptera is 2.8-4.9 mm.

The large chicory aphid does not host alternate, but lives all year on the upper parts of stems of chicory (Cichorium spp.). It is also frequently recorded from other related composite genera, including Crepis, Hieracium, Hypochaeris and Lapsana, suggesting it is less host-specific other Uroleucon species.  Sexual forms appear in September, and the species overwinters in the egg stage. Uroleucon cichorii is distributed throughout Europe and into Asia.

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Uroleucon cirsii (Large thistle aphid)

This rather large aphid is a bronzy or reddish brown with pale legs that are darkened towards the apices of the segments. Abdominal hairs are placed on pigmented scleroites. Spinal scleroites are fused into larger sclerites, each normally with three hairs. A crescent shaped sclerite is present in front of each siphunculus. The siphunculi are 0.25-0.34 times the body length, and 1.6-2.2 times the length of the cauda, with polygonal reticulation on less than the distal 0.25 of their length. The slightly dusky cauda has 20-33 hairs.

The large thistle aphid is one of several species of aphids that lives on the leaves and stems of the creeping thistle (Cirsium arvense) and related species.

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Uroleucon grossum (Large hawksbeard aphid) = Uroleucon cichorii grossum

Apterae of Uroleucon grossum are shining metallic brown with black antennae and siphunculi, and a pale yellow cauda. Their legs are mostly black, but the basal parts of the femora are pale and the middle parts of the tibiae are brown. Uroleucon grossum antennae are about as long as body. Their body length ranges from 2.7 to 4.4 mm.

Uroleucon grossum body hairs are placed on distinct scleroites, and there are crescent-shaped antesiphuncular sclerites. The ratio of the length of the siphunculi to that of the cauda is 1.3 to 1.7. The last two (fused) segments of the rostrum is 1.04 to 1.33 as long as the second tarsal segment (see second picture below). The alate female Uroleucon grossum has rather large marginal sclerites.

Uroleucon grossum does not host alternate but lives all year on the upper parts of stems of Crepis species. Sexual forms appear in late summer, and the species overwinters in the egg stage. Uroleucon grossum is distributed throughout Europe to Siberia and Mongolia.

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Uroleucon hypochoeridis (Large cat's ear aphid)

This is a large pinkish-grey aphid with pale legs that are darkened towards the apices of the segments. Abdominal hairs are placed on pigmented scleroites and the crescent-shaped antesiphuncular sclerites are prominent. The coxae are dusky or dark, darker than the basal parts of femora. The cauda is pale usually with about 17 hairs. The apical segment of rostrum is rarely longer than segment 2 of the hind tarsus. The nymphs are grey with a reddish-pink suffusion around the bases of the siphunculi.

The large cat's ear aphid lives on the stems of cat's ear (Hypochoeris radicata) and related species.

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Uroleucon jaceae (Large knapweed aphid)

Uroleucon jaceae is a large blackish aphid. The abdominal tergites 2-4 often have small marginal tubercles about the size of hair bases. The femora have the basal half pale and distal half dark, with a rather sharp transition between them. The tibiae are totally black. The siphunculi are reticulated over the distal 0.16-0.27 of their length and are 1.3-1.8 times the length of the cauda. The cauda is dark and bears 18-30 hairs. The body length of Uroleucon jaceae apterae is 3.0-4.5 mm long.

The large knapweed aphid lives on various knapweeds (Centaurea spp.) and a few other species of Asteraceae.

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Uroleucon jaceicola (Yellow-legged knapweed aphid)

Apterae of Uroleucon jaceicola are dark bronze-brown. Body hairs are strong, pointed and placed on rather large scleroites. Their coxae are dark, but the legs are yellow apart from black knees and black apices to the tibiae (compare with Uroleucon jaceae  which has wholly dark tibiae).

Image of aptera: guest image copyright Nigel Gilligan, all rights reserved

Uroleucon jaceicola siphunculi are black (although they may be paler in summer than in spring) and are 2.0-3.0 times the length of their cauda. The cauda is pale and bears 9-18 hairs (cf. Uroleucon jaceae which has a black cauda). The body length of the aptera is 2.9-3.3 mm.

Uroleucon jaceicola lives on the stems of common knapweed (Centaurea nigra). In spring it is found mainly low on stem, but moves to the upper parts later on. Oviparae and very dark apterous males of Uroleucon jaceicola have been found on the petioles of radical leaves in October. Uroleucon jaceicola is found in Europe, west Siberia and Central Asia.

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Uroleucon obscurum (Large hawkweed aphid)

Adult apterae of Uroleucon obscurum are reddish brown to bronze with black antennae and siphunculi and a yellow cauda. The body hairs are rather long, and placed on distinct scleroites. The femora are yellow basally and black on the distal half. The tibiae have the basal half yellowish brown. The apical segment of the rostrum is 1.06-1.29 times the length of the second hind tarsal segment. The antennal terminal process is 3.8-6.2 times longer than the base of antennal segment 6. The siphunculi are 1.1-1.6 times the length of the cauda. The body length of an adult Uroleucon obscurum aptera is rather less than for most species at 1.8-3.7 mm.

The large hawkweed aphid does not host alternate. It can be found on the upper parts of stems of hawkweed (Hieracium spp.). Sexual forms appear in September, and the species overwinters in the egg stage. Uroleucon obscurum is distributed throughout Europe and into Asia.

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Uroleucon picridis (Large oxtongue aphid)

Adult apterae of Uroleucon picridis (see first picture below) are dark shiny reddish brown, with black antennae and siphunculi. The legs are black with the basal half of the femora and middle part of tibiae light brown. The hind coxae are much paler than the distal parts of the femora. The dorsal hairs are borne on distinct scleroites, and there are also antesiphuncular sclerites and rather small marginal sclerites. The siphunculi are 1.4 to 1.7 times the length of the yellow cauda. The body length of the Uroleucon picridis adult is 3.3-3.6 mm.

The fused terminal segments of the rostrum (RIV+V) are 1.45-1.84 times the length of the second hind tarsal segment (HT2) (cf. Uroleucon cichorii where RIV+V is much shorter at 1.17-1.33 times HT2.) The alate female is much like the apterous female, except that the marginal and antesiphuncular sclerites are larger. The third antennal segment has 19-23 secondary rhinaria. The ovipara is much like the viviparous female but smaller. The winged male has a slender dark green body with antennae about 1.4 times the body length.

The large oxtongue aphid lives on its host ox-tongue (Picris) all year round. Apterous oviparae and slender dark green males can be found in October and November. Uroleucon picridis is found in most of Europe and across Asia, but not in the Scandinavian countries nor Denmark. In Britain it is restricted to the southern counties.

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Uroleucon pilosellae (Mouse-ear hawkweed aphid)

Identification:The apterae are dark reddish grey-brown with black siphunculi and a yellow cauda. The antennae are about as long as body. Well developed antesiphuncular sclerites are present. The tibiae have a paler middle section and the coxae are dark.

The ratio of the length of the fused last two segments of the rostrum to the length of the second tarsal segment is 1.2. The number of caudal hairs is 12 to 18. The ratio of the length of the siphunculi to that of the cauda is 1.7 to 1.8. The first tarsal segment has only 3 hairs, unlike most Uroleucon which have 5.

Hieracium pilosella is found on the flower stems of Hieracium pilosella and possibly other Hieracium throughout Europe. Laamari et al. (2013)  have recently recorded it on Leontodon hispidus.

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Uroleucon solidaginis (Goldenrod aphid)

Uroleucon solidaginis apterae are shining reddish brown, with rows of dark hair-bearing scleroites. Their antennae are longer than the body. Uroleucon solidaginis antennae and legs are mainly yellowish brown with the apical parts of the femora, knees and tips of tibiae dark. The third antennal segment is as dark as the rest of the antennae.

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 goldenrod aphid is found on the upper parts of goldenrod (Solidago virgaurea). It does not host alternate. Oviparae and alate males can be found from mid-July to October. Uroleucon solidaginis is found in Europe, Asia, north Africa and North America.

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Uroleucon sonchi (Large sowthistle aphid)

This is a large smooth dark brownish aphid with a glossy shine. Dorsal scleroites on abdominal tergites 1-5 are either absent, or very small. A crescent shaped sclerite is present in front of each siphunculus. The siphunculi less than twice as long as the cauda. The coxae are dark.

The large sowthistle aphid lives on sowthistle (Sonchus spp.) especially common sowthistle (Sonchus oleraceus) and prickly sowthistle (Sonchus asper).

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Uroleucon tanacetii (Crimson tansy aphid)

Apterae of Uroleucon tanaceti are red, reddish brown or crimson, with yellowish antennae and black apices. The legs are 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

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.

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Uroleucon taraxaci (Bronze-brown dandelion aphid)

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.

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.

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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.L. & Eastop, V.F. (2006). Aphids on the world's herbaceous plants and shrubs. Vols 1 and 2. John Wiley & Sons.

  •  Heie, O.E. (1980-1995). The Aphidoidea, Hemiptera, of Fennoscandia and Denmark. (Fauna Entomologica Scandinavica) E.J. Brill, London