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Uroleucon pilosellae

Mouse-ear hawkweed aphid

Identification & Distribution  Biology & Ecology 

Identification & Distribution:

In life Uroleucon pilosellae apterae are dark reddish grey-brown with black siphunculi and a yellow cauda. The antennae are about as long as the body.

 

Well developed antesiphuncular sclerites are present (see micrograph of Uroleucon pilosellae aptera in alcohol below left; note antennae are damaged in this specimen). The tibiae have a paler middle section and the coxae are dark (see micrograph below right).

 

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 (see below right), unlike most Uroleucon which have 5.

The clarified slide mounts below are of adult viviparous female Uroleucon pilosellae : wingless, and winged.

 

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.

 

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.

Acknowledgements

Our particular thanks to Roger Blackman for images of his clarified slide mounts.

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

  •  Laamari, M. et al. (2013). New data on aphid fauna (Hemiptera, Aphididae) in Algeria. ZooKeys 319, 223-229. Full text