Little slug type things on Caulis??

Hi,
My Caulis are doing really well, and when I was inspecting them for any caterpillas etc, I found them to have some small see through thing that looks like a slug with a red stripe in it's back. When you squish them the red comes out more orange, they move quite quickly compared to a slug too.
Anyone have any idea what they are?? Thanks

Oh! I need them! Lots of them, everywhere would be good! Thanks for that, no more squishing then