Garden pest. Sawfly
To help you identify the Sawfly, here she is laying eggs in a rose stem.
The female uses her ovipositor to lay her eggs in plant stems. In this example a rose.
The tiny larvae emerge and grow quickly as they devour the leaves. 
When disturbed they all lift and wave their rear ends. This is designed to frighten off any birds wanting to eat them.
Photography By Neil Bromhall – Complete Gardens Advice CD-ROM
Posted by Neil Bromhall 
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