The body length of Pterocallis alni apterae is 1.3 to 2.0 mm. Both the winged and wingless adult viviparae of P. alni are yellowish white to yellowish green. For a more detailed description of this species please use the ‘Further info:’ link below.

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In Britain Pterocallis alni is found almost exclusively on Common Alder, living dispersed on undersides of leaves.

Sexual forms occur about September-November.

Sometimes attended by ants.

True status in Britain is difficult to determine due to lack of records.

Rarely recorded in Leicestershire and Rutland.

https://influentialpoints.com/Gallery/Pterocallis_alni_Common_alder_aphid.htm