EPOW - Ecology Picture of the Week

Free Rides

Chalky Percher (Diplacodes trivialis), Family Libellulidae
Litchfield National Park, Northern Territory, Australia

Explanation:  We've seen this before, but on a different continent and hemisphere!  

Those aren't decorative beads on the thorax and abdomen of this dragonfly.  They are mites, grabbing a free ride.  

This dragonfly has the colorful name Chalky Percher, a common odonate insect found widely in Asia and Australasia.  They breed in ponds, wetlands, "billabongs," and other wet sites.  I shot these photos while exploring Tabletop Swamp in Litchfield National Park of "Top End," Northern Territory, Australia.  

But it's the mites that are the story here.  They are engaged in phoresis or phoretic behavior, which means that they have attached themselves to another organism for the purpose of transport.  This helps disperse the species -- the mites, here -- to new habitats and locations, to keep their populations viable and well distributed.  Many invertebrates use phoresis to move about -- think of ticks, lice, fleas, leeches, and much else.  

So, we've seen how mites attach to dragonflies, here in northern Australia, previously in Washington, USA, and many other locations.  It is a common ecological function found globally. 

All aboard!