Aphis gossypii

The blackflies depicted here on a shoot of tutsan (Hypericum androsaemum) have been identified by Bob Dransfield, the national aphid recorder as Aphis gossypii, the cotton or melon aphid.

This is a widespread pest in the tropics but not so frequently recorded in Britain.  It can easily be confused with two other aphid species, Aphis chloris and an unnamed Aphis.

Although they are a difficult group, much progress in the identification of British aphids can be made by using this web site: http://influentialpoints.com/Blog/How_to_identify_aphids_from_photos--the_basics.htm