I macro photographed a drone fly a few days ago and noticed there were 3 red 'blobs' on the top of it's head between the eyes. See photo uploaded. They are more or less equally spaced forming a triangle.
I would like to know what they are please?
You have found the ocelli, or simple eyes, that several insect orders have on top of their heads.
Here is a good summary: https://en.wikipedia.org/wiki/Simple_eye_in_invertebrates