unknown sawfly on Alchemilla

Alchemilla xanthochlora, Belgium, prov. Namur, Graide © Jean-Yves Baugnée

Tenthredinidae on Alchemilla xanthochlora

underside

parasite

Probably this is an oviposition scar caused by a sawfly, fam. Tenthredinidae. That would explain the slight swelling and the tiny wounds at the upper side. It is known of several sawflies that the freshly emerged larvae live endophytically for a short time, before starting to live freely. There are sawfly species known displaying this behaviour (like Empria testaceipes), but without knowledge of the larva an identification is not possible. (Thanks to Andrew Liston and Marko Prous for comments.)

mod 28.v.2018