These little 'cats' are the offspring of Monarch Butterflies that made it through the migration from Mexico to Canada (or the butterflies that were hatched along the way). It's exciting to see them in the garden. This milkweed (Asclepias syriaca, commonly called common milkweed, butterfly flower, silkweed, silky swallow-wort, and Virginia silkweed) is growing in the front garden.
You can learn all about the Monarch Butterfly and their caterpillars at the Canadian Wildlife Federation website.
As a side note, it's also nice that milkweed has an absolutely intoxicating scent. Why are there not milkweed perfumes? Maybe that's another thing that we will need to try to make here at Bentpath Getaway?