tiny black dropping under orchid

[kkdcalgary]

Dear All;

I have noticed in the past month or so that a few of my orchids will have scatterings of black stuff under them when I pick them up to water. At first I thought it was degrading medium but on closer inspection they are tiny cylindrical droppings about 1mm long. The plants are doing fine so I assume it's some sort of insect feeding on the medium. It's happening under my Maxillara tenuifolia and Brassia rex 'waiomao spotless'. Is this something to worry about?

thanks!
Karen.