Two images of Meadowhawks with red, round egg-like parasites attached to the body. According to Mr Google, these are most likely larval water mites that attach themselves to the Dragonfly Nymph and then to the Dragonfly when it emerges.

The mites,reportedly, feed on the Dragonfly blood for a few weeks and eventually return to the water. It is stated that in most cases the parasites do not appear to significantly harm their hosts - all as per google search for "eggs on a Dragonfly".