Uroleucon pilosellae

Identification & Distribution:

In life Uroleucon pilosellae apterae are dark reddish grey-brown with black siphunculi and a yellow cauda (see first two pictures below). The antennae are about as long as the body. The fused apical segments of the rostrum (RIV+V) are about 1.2 times the length of the second tarsal segment (HTII). Well developed antesiphuncular sclerites are present. The tibiae have a paler middle section and the coxae are dark (see micrographs below). The first tarsal segment has only 3 hairs (see micrograph below) (cf. Uroleucon cichorii and Uroleucon obscurum which both have 5 hairs on the first tarsal segment). The siphunculi are 1.6 to 1.9 times the length of the cauda (cf. Uroleucon obscurum which has the siphunculi 1.0-1.4 times the length of the cauda). The number of caudal hairs is 12 to 18. The body length of an adult aptera of Uroleucon pilosellae is 2.2-2.5 mm.

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

Uroleucon pilosellae 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.

Our observations appear to be the first, and only, record of Uroleucon pilosellae in UK on its host to date.
First observed	by: Influential Points	25 July 2013	at: Dundreggan estate, Scotland

Biology & Ecology

Whether Uroleucon pilosellae is both specific to Hieracium pilosella and is the only Uroleucon regularly feeding on this plant is unclear. Heie (1980-1995) states explicitly that the otherwise very similar Uroleucon cichorii does not occur on this plant, whilst Blackman & Eastop (2006) record 5 Uroleucon species on it, including Uroleucon cichorii.

The leaves of mouse-ear hawkweed (Hieracium pilosellae) are setose above and on the margins, and white beneath with long soft hairs (see below first).

The flower bracts and stem are clothed with dense stellate, glandular and pilose hairs (see above second). These characteristics are markedly different from other Hieracium species, so it would not be unreasonable to expect that a different species has evolved to exploit Hieracium pilosellae.

Other aphids on same host:

Uroleucon pilosellae has been recorded on Pilosella officinarum, Pilosella caespitosa, Hieracium aurantiacum, Hieracium bauhini, Hieracium cymosum, and Hieracium echioides.

• Blackman & Eastop list 18 species of aphid as feeding on mouse-ear hawkweed (Hieracium pilosella = Pilosella officinarum) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 15 as occurring in Britain (Show British list).

• Blackman & Eastop list 13 species of aphid as feeding on orange hawkweed, fox-and-cubs (Pilosella aurantiaca = Hieracium aurantiacum) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 11 as occurring in Britain (Show British list).

Acknowledgements Our particular thanks to Roger Blackman for images of his clarified slide mounts. Whilst we make every effort to ensure that identifications are correct, we cannot absolutely warranty their accuracy. We have mostly made 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 Laamari, M. et al. (2013). New data on aphid fauna (Hemiptera, Aphididae) in Algeria. ZooKeys 319, 223-229. Full text