Most years we get troupes of larvae of the sawfly Nematus pavidus eating the leaves of the goat willows (Salix caprea) in the window box (see entry on 21st September 2008). There are usually two generations in spring and summer.
This year the spring generation performed as normal, turning many leaves to fretwork and some just to a midrib. The second generation also started off well, but went into a decline a week or so ago. Today I could only find one or two sickly individuals, but noticed the predatory mirid bug Heterotoma planicornis running about where the sawfly larvae had been. They pierce their victims with the proboscis and suck the juices out.
Though not obvious from the photo this is a very distinctive insect with flattened second antennal segments and slender whitish ones beyond these. This rather poor picture gives a better idea.
The bug is quite small, so maybe it had some help in eliminating the sawflies.