Caterpillar identification

Hi all I found this caterpillar last week on my freshly laundered and folded jeans. I think my cat must have brought it in somehow as he escaped the day before.

I have searched all over the internet but can't seem to identify it. It was very small and dark to start with (see first photo on collage) but has now shed and is much bigger maybe 6cm or so fully outstretched and has turned to a greenish colour with stripes, prominent small black spots and sparse hairs. It also has a 4 red coloured spots towards its head. I was mainly concerned about feeding it but as it's devouring the lettuce I have provided I'm now just curious. Thanks!


Reddish spots near head can be seen on this picture difficult to make out though.