Raspberry problem

My raspberries were doing great and after we came back from london we noticed some leaves looked like skeletal lace, the rest of the green had been munched.

On closer inspection we found lots of evil looking caterpillars. we are squishing them by hand but what else can we use as its alot of murdering by hand 

I had a look at google and I thing its sawfly 

'Bug Clear Gun for Fruit and Veg' is sposed to work against caterpillars as well, according to Amazon, anyway! 

oh great think I may have some of that