Aphids (subfamily Eriosomatinae) are not easy to identify to the exact species. We believe these may be Blue Ash Aphids or Smokey-winged Ash Aphids. Similar to the swarms of Woolly Aphids that are currently everywhere, these tiny (but incredibly numerous) insects are in the middle of their fall migration. But rather than a migration that’s measured in miles, this migration is from one type of tree to another …generally from the roots of Douglas firs to ash trees where they will lay eggs that will overwinter. As you can see, our observer found “a few” of them on an American Ash. 

Size: Very small

Photo by: Joe Glassy on 10/4/21 in Missoula, MT