These little creatures appeared when I enlarged a photo of a broad-bodied chaser nymph from my pond. It's not clear whether they are parasitic on the dragonfly nymph, but I suspect they were accidentally deposited on its back as the water drained away. Are they water lice? Or nymphs of something larger? I appreciate they will be difficult to pin down to a species from these photos, but I'm curious to know what they are likely to be.
No photos on your post.