Insect and Spider Identification: dirt / droppings / leaving on window sill, 1 by extremez

extremez wrote:
Hi Everyone,

About four times in the past year ive discovered a window sill in our house quite dirty, each time I vacuum the area. Its behind a filling cabinet so I don't check there often.

Today I noticed it again, so instead of vacuuming the area, I decided to find out what was making the mess. Upon searching google I didn't find anything that looks the same, but I did find a picture of termite droppings which looked similar, which is very concerning.

I have seen normal black ants coming in from the window sill in the past, but not recently.

The three pictures I have uploaded are of the window sill, window sill zoomed in and carpet next to window sill where there seems to be a few dead and and millipedes.

Any help identifying what made the mess would be very helpful, thank you in advance.