A coworker brought in a yellow flower his students had picked, surprised at the ants climbing on it. Since I was eager to use my digital microscope, we set it up and had a look at the base of the flower. With the naked eye, we could barely see a few uninteresting lumps. They were forgettable until we looked through the 'scope.
Ants & Aphids.
More from Ars Technica and Science Daily.
Many students wanted to study ants as their project and I mostly dissuaded them. The challenge is in identifying what species we are looking at. 'Around 5 mm and black' covers a lot of ground in the ant books.
Aphids are similarly hard to ID. There are a lot of them and as you can see, they are tiny.