Allotments 4 All

Hiya,

Just curious really.  I noticed that my next door neighbour's willow is infested with tiny black caterpillars that are eating the flesh part of the leaves and leaving the veins and stems.  They all gather around the edge of a leaf and wave in the wind and, in essence, look like part of the leaf.  I have pointed them out to my neighbour, who is a tree surgeon and he's going to get a spray, but I just wondered whether anybody would know what moth or butterfly they are caterpillars of?

Shamba

They sound more like sawfly larve. There are a number specific to willow.