May 11th lilac leaf problem

Today I noticed that many of the new leaves on an 8 yr. old lilac have been sliced by some insect. The damage is not in the shape of holes but a scissor-like cutting of the leaf. I looked for the culprits and none appeared. Perhaps they return to the ground during the day?............help!

 

Giving us a few pictures would really help with identifying this problem.

 

Thanks for the reply, I'm useless with photos on the the internet. The leaves are simply sliced rather than chewed in one part.