Demodex

Last year to celebrate October and the spooky season, Ferrebeekeeper presented a series of posts concerning the mythological monsters born of the Greek snake goddess Echidna.  Those monsters were really big and really scary but, in the end, the operative word was “mythological”–they didn’t actually exist.  This October I have decided to pay closer heed to the real world as we celebrate the horrifying, the macabre, and the eerily beautiful.  To start with, I have already presented a dead city surrounded by ancient desiccated mummies and nuclear test sites! But I’m guessing that Xinjiang is pretty far away from all but a handful of my readers, so today I wanted to focus on a horror closer to hand.  In fact today’s subject is even closer than that—there are 50/50 odds that there are some of these parasitic mites crawling in your eyelids even as you read these lines.

Coloured scanning electron microscope photo of Demodex folliculorum (from Sciecephotolibrary)

I am writing about Demodex, a genus of tiny parasitic arachnids which live in or around the hair follicles of mammals.  There are more than 50 known varieties but two species in particular (Demodex folliculorum and Demodex brevis) are endemic to human hosts. The mites are approximately 0.4 mm long, with eight extremely short legs.  Covered with adhesive scales, the mites are semi-transparent. According to Buzzle.com, “The needle-like mouth-parts feed on the dead, flaky skin-cells, hormones and the sebum which accumulate in the hair follicles.”  Buzzle goes on to note that while the mites are usually harmless an unusually large number can cause demodicosis, a sort of mange.  Although I gave a 50/50 breakdown in the first paragraph, that number seems to have been made up by dermatologists to keep squeamish people from ripping all of their eyelashes out.  Odds are if you have walked the green earth long enough to see adulthood, you have played host to these eyelash mites.

Demodex brevis seen under a conventional microscope

This topic seemed fun when I started, but I honestly have not been able to keep my fingers out of my eyes while writing and I am now squinting at the screen through itchy, puffy eyes.  Nevertheless there is an important point behind all of this.  It isn’t just coral reefs and aspen colonies which form habitats for other living things. Every lifeform is an ecosystem with parasites, symbiots, and weird alien neutrals–even us.