"Amy Stone reported that BRISTLY ROSESLUG SAWFLY (Cladius difformis) remains active and is continuing to produce the distinctive "windowpane effect" on rose leaves in northwest Ohio. This type of feeding damage is also characteristic of other members of the "roseslug sawfly complex" including ROSESLUG (Endelomyia aethiops), and the CURLED ROSE SAWFLY (Allantus cinctus). However, only the bristly roseslug continues to feed throughout the season."

From:

http://bygl.osu.edu/content/slugged-rose-leaves-0

Here is a link that might be useful: link for above