So we have these tiny, 1 cm long, shiny black head, 1mm thick body, plus dark hairs – caterpillar dropping down from everything. I think they are biting but maybe they are stinging and the bites hurt. Please help identify, I attached a picture but not sure if good enough.
Thank you for contacting the Toronto Master Gardeners.
There are a number of possibilities for your caterpillar. The type it is depends on small markings and colour on the back. from your photo it is difficult to tell if there are any different colourings or markings on the caterpillars back.
My suggestion would be to bring a sample into a horticulturalist at your local nursery. They might have seen a number of these caterpillars from other homeowners. This website illustrates a few of the more common caterpillars that you would find in Ontario.