Aphis pilosellae

Identification & Distribution:

Adult apterae of Aphis pilosellae are pale to dark green, most commonly mottled green. Immature aphids are paler (see pictures below). Large apterae have dusky bands across tergites 7-8 or 6-8; small apterae have only faint dusky bars on 7-8. The most distinctive character of Aphis pilosellae is the long apical rostral segment (see first photomicrograph below) which is longer than antennal segment IV or V. The marginal tubercles on abdominal segments 1 and 7 are rather large (see second photomicrograph below).The siphunculi are 0.80 to 1.25 times the length of the cauda, which is tapering with very strongly incurved hairs. The body length of the Aphis pilosellae aptera is 1.02-1.54 mm.

The alate Aphis pilosellae has marginal and postsiphuncular sclerites, bands on tergites IV-VIII, and often bars on a variable number of tergites I-V.

The micrographs below show ventro-lateral and ventral views of an adult aptera Aphis pilosellae in alcohol.

The green mouse-ear hawkweed aphid lives under the rosette leaves and on the stolons of mouse-ear hawkweed (Hieracium pilosella). It is sheltered by ants under tents of soil particles. Sexual forms exist, but have not been described. In Britain it seems to be restricted to the south-east, possibly because it needs high sunshine levels. Aphis pilosellae is found throughout Europe and into Russia.

Other aphids on same host:

Blackman & Eastop list 18 species of aphid as feeding on mouse-ear hawkweed (Hieracium pilosella = Pilosella officinarum) worldwide, and provide formal identification keys.

Of those aphid species, Baker (2015) lists 15 as occurring in Britain: Aphis gossypii, Aphis pilosellae, Aulacorthum solani, Brachycaudus helichrysi, Macrosiphum euphorbiae, Myzus ornatus, Myzus persicae, Nasonovia compositellae ssp. nigra, Nasonovia pilosellae, Nasonovia ribisnigri, Pemphigus bursarius, Trama troglodytes, Uroleucon cichorii, Uroleucon obscurum and Uroleucon pilosellae.

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).

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