Attachment may be a basis for specialization in oak aphids

The potential role of tarsal attachment in host selection was studied in the specialist aphids Tuberculoides annulatus Hartig and Myzocallis schreiberi Hille Ris Lambers and Stroyan. M.schreiberi could walk freely on its host, Quercus ilex and on Q.robur , whereas T.annulatus could walk freely on its host, Q.robur but had difficulty on Q. ilex. Attachment to the rough‐textured leaves of Q.robur was achieved by means of the pretarsal claws, and to the smooth upper surface of individual trichomes on the lower surface of Q.ilex using flexible pretarsal empodia. Both behavioural and allometric differences can account for the inability of T.annulatus to grip onto Q.ilex. The role of attachment by phytophagous insects in host plant resistance and selection is discussed.