[cc]

Black poo or eggs. Pretty sure it's caterpillar poo.
Either way see pictures and note I washed some leaves put them in the fridge and more poo/eggs appeared and then I found a caterpillar in there who clearly didn't have problem with the cold. Sorry didn't take picture of it. Green and probably underneath the leaves.
Any ideas on getting rid of them.
I was thinking of a light watering and check the soil. They are on mixed salad leaves.
PS which butterfly laid it??
Thank you for your time cc

[Subversive_plot]

That does look like caterpillar frass (poo). I can't completely rule out a different insect. Sorry, can't tell from a photo what variety of moth or caterpillar larvae it came from.

Added later: sorry, missed your comment about finding a caterpillar.

Products for the vegerable or flower garden that contain Bacillus thuringiensis as the main ingredient will safely deal with caterpillars. Usually a dust, but there are also liquid products.

[cc]

That does look like caterpillar frass (poo). I can't completely rule out a different insect. Sorry, can't tell from a photo what variety of moth or caterpillar larvae it came from.

Added later: sorry, missed your comment about finding a caterpillar.

Products for the vegerable or flower garden that contain Bacillus thuringiensis as the main ingredient will safely deal with caterpillars. Usually a dust, but there are also liquid products.

Have you used it? And if so  can you tell me the name of the product?
Thank you for your time

[Subversive_plot]

That does look like caterpillar frass (poo). I can't completely rule out a different insect. Sorry, can't tell from a photo what variety of moth or caterpillar larvae it came from.

Added later: sorry, missed your comment about finding a caterpillar.

Products for the vegerable or flower garden that contain Bacillus thuringiensis as the main ingredient will safely deal with caterpillars. Usually a dust, but there are also liquid products.

Have you used it? And if so  can you tell me the name of the product?
Thank you for your time

Dipel dust and Thuricide (liquid) are two trade names you would see on this side of the pond.  I have used both, they work when used as directed.  The dust form has a longer shelf life, but you need equipment for applying the dust (not free, but not terribly expensive either).  Product trade names may be different over there, maybe someone on your side of the pond can make a recommendation?