Rhinoceros Beetle Larvae and associated Mites

They represent incredible huge insects, their closest relatives live in the tropical zones, but they are indeed native to Europe: European Rhinocerus beetles (Oryctes nasicornis).

As many other insects too, they usually do not live completely alone, but have cohabitants on their bodies. This even concerns the big beetle larvae, which are visible in this footage.

They carry phoretic nematodes and, most conspicuous: greater numbers of mites.

These mites of the taxon Mesostigmata belong to the clade Laelapidae. When such mites take a ride on an insect, then this can have different reasons. They might be phoretic, which means that they are just carried from one habitat to another, but they also might be parasites. Parasites do not need a transport, but get on an insect, sometimes as their final destination. That's were they might spend the rest of their lifes and from what they are feeding. This way they can harm the corresponding insect, but usually don't kill it.

Another possibility is a more neutral association than parasitism: mite might feed on components, being different kinds of excreta of this insect. They then would may be even support the hygienic conditions of their insect.

Mesostigmatid mites, found on the rhinoceros beetle larvae in my footage, are definitively not phoretic as they visibly feed on their hosts. But it's not recognizable, whether they suck blood (hemolymph) of these beetle larvae or whether they "just" feed on any secretions in the areas of the larvae's coxae, where they usually sit.

The herewith in my footage presented mites might represent a member of the genus Hypoaspis (H. krameri, H. canestrini or similar species). If this determination on the genus level should be correct, then there might be indication for a real parasitism as another species, Hypoaspis polyphyllae, was for example identified to puncture the larvae cuticles of the scarabid beetle Polyphylla olivieri (Khanjani and Ueckermann, 2005).

From the evolutionary point of view, it's always interesting to ask, whether parasitism in a clade of animals evolved from phoresy or whether phoresy even evolved from parasitic assiciations.

These larvae of the European rhinoceros beetle were found at the Gulf of Naples (Italy) in a small oak forest.