48,200 species have already been identified and scientists postulate that this figure is only five per cent of the total number of mites on Earth. They are strong (for their size), durable and – most importantly – highly adaptable to change, evolving quickly to exploit the different environments presented to them over millions of years. In fact they have proved so good at adapting to Earth’s changing environment that mites – or more accurately, their sub-class Acari – have lived on Earth since the early Devonian period (416-359 million years ago), inhabiting the warmest and coldest climates and a vast array of living creatures. This evolutionary adaptability has granted mites almost unparalleled diversity and now, with the advent of the electron microscope, their numbers and types are visible for the first time.
Take the common house dust mite (Dermatophagoides pteronyssinus) from the pyroglyphidae family. This variant of mite dwells in human residences – including, as probability suggests, your home – and feeds entirely on organic detritus such as flakes of shedded human skin, flourishing in the stable environment and on the perpetual food supply. The dust mite is tiny and unseen, with a size of roughly 420 micrometers in length and 320 micrometers in height, highly reproductive – a female mite will lay 60 to 100 eggs in the last five weeks of her life – and impervious to all temperatures between 0°C and 60°C.
In essence, the dust mite is perfectly suited for life on Earth now, with the numbers of humans and houses in suitable climates (count yourself immune then in you live in Antarctica) in abundance. The ancestor that the common dust mite once shared evolved to take advantage of the rise of mammals (especially those which emerged from the nomadic tribal groups to set up permanent residences) and did so extraordinarily quickly. For while modern humans have only been around for 125,000 years, the Acari sub-class, as aforementioned, has been around for over 400 million.