Tuesday, July 7, 2015

Dragonflies Get "Fleas" of a Sort,Too

I recently posted a photo of a male Tule Bluet (Enallagma carunculatum) with ectoparasites on a Google Plus post+Bette Kauffman commented on the presence of "mites" on this damselfly; +Didier Houbrechts expressed that mites were also "in Europe and on dragonflies too"  and +viviane godenne weighed in "seen in Belgium also...sometimes in impressive numbers."

So, I did some research on this. Found several references that researched these parasites. And yes, they are mites, Water Mites (Arrenurus sp.) to be more precise. Corbett (1999) is cited by R. J. Andrew et al [Journal of Threatened Taxa 7(1): 6821–6825] having identified 55 species of mites that are parasitic on Odonates. Andrew et al went on to identify 7 species of dragonfly with mite infestations in central India; only 9.3% of the 365 sampled odonates had mites. The main attachment site was the thorax and females (39%) had more mites than males (9%).

The mites attach to adult dragonflies as these insects morph from their aquatic form to terrestrial form. Mites mainly chew through the dragonfly exoskeleton where "plates" intersect and are "structurally weak". However, there instances of mites attaching to the wings, here is a link to Google Images illustrating this.

A. Zawal [Biological Lett. 2006 43(2) 257-276] researched water mites in northwest Poland and found the mites infested nine species of damselfly. The rate of attachment was 77% with high numbers per host animal (up to 195). Attachment sites were the thorax and the abdomen.

The mites engorge on the host dragonfly expanding to 140 times original size (M. R. Forbes et al Experimental and Applied Acarology 34: 79–93, 2004). They drop off the host dragonfly when the odonates return to the water to breed. Forbes et al overview research that indicates mites (few or many) affect their hosts in a negative fashion though effects aren't consistent.

Most interesting correlation is the coloration of mites as they mature; all attached mites change color with age in a synchronous pattern [R. Mitchell American Midland Naturalist
Vol. 82, No. 2 (Oct., 1969), pp. 359-366]. Mitchell proposes this is one way an odonate can be also aged; it has been done with mosquitos!

So here are a couple of my photos of what you can now look for and add to the science of this subject :-)

Cherry-faced Meadowhawk

Lestes sp.