This looks like a set of galls caused by the midge Iteomyia capreae. See http://www.bladmineerders.nl/gallen/dip … apreae.htm (rapidly becoming most useful site for galls as well as leaf mines).
PS. For former WABbers, yes it is me (how not with nature of post). Will probably mainly lurk & be v. occasional contributor, as busy with other things too (see http://www.economist.com/news/internati … -world-has (paywall)).
