News from ABC on Feb. 21, 2013: http://www.abc.net.au/science/articles/2013/02/21/3695174.htm  

By Jennifer Viegas, Discovery News

Paleontologists used to think that dinosaurs had fleas and other parasites, but now a new study concludes that the insects were actually aquatic or amphibious flies.

The study, published in the journal Nature, focuses on enigmatic Jurassic insects called strashilids. The same team that originally speculated about the fleas has revised its original theory.

Diying Huang of the Nanjing Institute of Geology and Palaeontology and colleagues first thought that strashilids were huge fleas.

Closer investigation of the Jurassic insects finds that they weren't parasites. Previously, their pincer-like legs were thought to help the insects cling to hosts. Huang and the other researchers, however, propose that they were used for grasping mates during copulation.

This theory gets a boost from fossils showing the insects having sex (see image below).

In addition to this rather voyeuristic discovery, the researchers noticed that males possessed abdominal respiratory gills. These point to a life in the water.

The creatures appear to have been highly specialised winged insects instead of parasites. They shed their wings shortly after emergence and then crawled into the water to mate.

They appear to have lived at the same time dinosaurs did, leading to a case of mistaken identity.