A look online (I Googled 'Black beetle with orange antennae') suggested it was a Black Sexton Beetle, Nicrophorus humator, since confirmed by my far more learned colleague, Nick Martin (who knows the right people). Black Sexton Beetles are a common species of Silphidae (carrion beetles) that are active fliers and readily come to light. What I couldn’t fail to notice was that it was covered in large reddish mites. My first reaction was that it was being eaten alive and we faced the same dilemma that the BBC film crew from 'Dynasties' had when they rescued the penguins out of a ravine. Should we try and remove them? We decided not to (mites deserve a living too) and are very glad we didn’t, as the reality was very different to what I initially believed.

The mites are in fact taking advantage of the beetle’s parenting instincts. Carrion beetles such as Necrophorus demonstrate an advanced level of brood care. The parents will bury carrion and inject it with fluids to ensure it doesn’t decompose too quickly. They excavate a brood chamber around the carrion where their young will hatch and feed on the carcass. However, the parents are not always alone and this is where the mites come in.

The mites are Poecilochirus carabi and are phoretic meaning they are using the beetles to carry them around to help dispersal and take them to other food. The mites also breed in the brood chamber. The parent beetles don’t leave the chamber immediately, they initially look after the larvae and get rid of any pests that could predate on them. The male beetle typically leaves the chamber after a couple of days and those mites that hatch in time hitch a ride. Other mites will leave a few days later on the female beetle and the rest will bide their time waiting for the beetle larvae to develop into adults and then disperse on them. The mites that hitch a ride are deutonymphs (the last development stage before adults) and don’t yet have mouth parts so couldn’t have eaten the beetle even if they wanted to. The mites actually eat the eggs of other invertebrates such as Diptera (flies).

The Necrophorus provides the perfect host. They are a relatively large beetle, highly mobile and will take the mites precisely to the food sources they need. It is not clear what advantages or disadvantages having so many passengers has on the beetle. Our beetle didn’t seem too fussed and after posing for photos wandered off perfectly happy into the undergrowth with its retinue in tow.