House Dust Mites
A study by Scanning Electron Microscopy into these tiny creatures.
copyright Andrew Syred

"The least of Reptiles I have hitherto met with, is a Mite, a Creature whereof there are some so very small, that the sharpest sight, unassisted with Glasses, is not able to discern them... Notwithstanding which minuteness a good Microscope discovers those small movable specks to be very prettily shaped Insects ..."

So wrote Robert Hooke in 1665 in his widely acclaimed work `Micrographia' dedicated to King Charles II amidst the last great plague of London and a year before the great fire which destroyed 13,000 buildings but surprisingly claimed the lives of only four people. Certainly fraught times for a Londoner to live through, whilst concerning himself with dust mites.

The house dust mite is neither a reptile or insect but until Carolus Linnaeus brought some assemblage of order into classification in 1757 with his Systema Naturae, a scheme of binomial nomenclature, little serious attention was paid to such detail. Employing his very basic microscope with poor lenses, Hooke described the mites in considerable detail with remarkable accuracy carefully stressing the ".. eight well shaped and proportioned legs ..." if comparing them still further with crabs and lobsters. Had he lived to see the 300th anniversary of his work, he would have witnessed the marketing of the first commercially available scanning electron microscope, by Cambridge Instruments, which surely would have astounded him.

Modern classification places mites with the spiders and though their classification appears to be in a state of flux, house dust mites may be classified as follows:

Phylum	- Arthropoda
Class	- Arachnida
Order	- Acarina
Sub-Order	- Sarcoptiformes
Division	- Astigmata
Family	- Epidermoptidae
Genus	- Dermatophagoides
Species	- D. farinae, D. pteronyssinus

It is alleged that house dust mites inhabit our homes by the millions; our beds, furniture and carpets are over-run with them. Manufacturers of vacuum cleaners and producers of mite-proof, `anti-allergenic' fabrics for bedding materials market their products by trading excessively on this general perception. Adult mites are very small, approximately 300um in length, so head to tail three or four approximately span a millimetre and are almost invisible to the unaided eye under normal conditions. Males tend to be smaller and more flattened than the female which takes on a rotund appearance especially when fully mature and carrying eggs.