Two Nicrophorus Beetle Species Plus . . .

Roundneck Sexton Beetle (Nicrophorus orbicollis)

Above is the roundneck sexton beetle that I photographed after capture (it was, of course, released after the photo session). You can see that the area after the head, called the thorax, but before the body, which is called the abdomen, is pure black. These beetles are attracted to moth lights, which is where I always find them. Sexton beetles are named after the people who look after a church and churchyard, and used to be gravediggers.

Tomentose Burying Beetle (Nicrophorus tomentosus)

Above is Jody's photo of a tomentose burying beetle. The thorax, between head and body, is covered with luxurious gold hair. That is how you can tell the two species apart. But there is one other behavior that tells them apart. The roundneck buries dead animals that it finds, and then feeds on them. The tomentose (also called the gold-necked carrion) digs a hole under the animal and covers the animal with leaf litter. Both species have antennae with orange-tipped clubs. They smell the bodies of the dead with those clubs, which are olfactory organs. 

Each of these beetles are in the family Silphidae which are carrion beetles. Carrion is "the decaying flesh of dead animals." Without carrion beetles, vultures, and other decomposers, we would be in a heap of trouble with dead animals piled a mile high.

All this is simply background to what fascinated Jody and I, though.  Look at my photograph of another roundneck beetle, and see if you notice a hitchhiker or two:

If you don't see them there, you will see them on Jody's tomentose: 

The little bugs on the beetles are Carrion Beetle Mites (Genus Poecilochirus). The mites are not doing a thing to the beetles except hitchhiking. This is called phoresis (one creature attaches itself to another solely to travel). The mites lay their eggs in dead animals, but they are tiny and the beetles can get them where they need to go quickly. The best, or biggest, example of phoresis  is a person riding a horse to go from one point to another. Another note about mites: they have eight legs, like spiders. But they are not spiders. They also are not insects.

Jody made a video of the beetle and mites. It may seem gruesome, but try to stick with it. The mites are not eating the beetle. They are, though, probably telling the beetle to get with it and take them to a carcass quick!

References:

• Bugguide: Species Nicrophorus tomentosus - Tomentose Burying Beetle
• Bugguide: Species Nicrophorus orbicollis - Roundneck Sexton Beetle
• iNaturalist: Carrion Beetle Mites
• National Park Service: A Symbiotic Relationship - Carrion Beetles and Mites
• Wikipedia: Phoresis

Nature Notes at Rambling Woods 2

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