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Identification & Distribution:

Both the winged and wingless adult viviparae of Pterocallis alni are yellowish white to yellowish green. Their antennae are ringed with black. The hind femur has a characteristic black spot near its apex. The tarsi are black. The body length of Pterocallis alni apterae is 1.3-2.0 mm.

 

The image below shows an apterous adult Pterocallis alni, in alcohol.

Pterocallis alni is found almost exclusively on common alder (Alnus glutinosa) in Europe, living dispersed on undersides of leaves and sometimes attended by ants. Sexual forms occur in September-November. The common alder aphid is common and widespread in Europe, east to Turkey, Iran and Lebanon and introduced to North America, New Zealand, Australia and Chile.

 

Other aphids on same host:

Blackman & Eastop list about 50 species of aphids  as feeding on alders worldwide, and provides formal identification keys for aphids on Alnus. Of those, Baker (2015)  lists 6 aphid species on common alder (Alnus glutinosa) as occurring in Britain: Clethrobius comes,  Crypturaphis grassi,  Glyphina betulae,  Pterocallis alni, Pterocallis maculata  and Stomaphis quercus. 

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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