I smiled when I saw Chris Packham getting excited about a beetle on tonight’s episode of Springwatch. It was not just any old beetle, but a colourful Sexton Beetle (Nicrophorus vespilloides), sometimes known as the burying beetle. I photographed this Sexton Beetle at work one summer and am grateful to the camp site manager for bringing it to my attention when he found it crawling on his jacket – despite him disliking bugs.
Like Chris, I too, think it is a fascinating beetle.
I put this beetle in a bug viewer for a few minutes as I reached for my Field Guide to ID it and it went crazy! It hurtled round and round at high speed and there was no way of getting a picture when in there. It seemed to be really annoyed by the mites which were crawling all over it. I just had time for one quick picture when I tipped it out of the container.
The Sexton Beetle or Burying Beetle get its name from the fact that the adults bury the corpses of small mammals and birds to feed their larvae. They fly well and are said to be able to scent a dead body up to two miles away. When the the burial is complete – a process which can take up to 8 hours – the adults strip off the fur or feathers. As they do this they coat the carcass with secretions which slow the decay processes and prevent the odour from attracting other animals. The female then lays the eggs in the soil nearby where they hatch after a few days. The larvae are able to feed on their own, but to speed their development the parents digest the flesh and regurgitate the liquidised food. If there are too many larvae for the size of the carcass the parents may reduce the number to suit.
These beetles are frequently infested by tiny reddish-brown gamasid mites (Gamasus species), like in the picture above. These mites cluster between the body segments, under the wing-cases and anywhere else that the beetle cannot easily reach with its legs to dislodge them.
I found the beetle fascinating, but, for some reason, felt a bit ‘queasy’ about the mites. Although the beetle appeared to be troubled by the mites this is a mutually beneficial arrangement.
The mites use the Sexton Beetle to travel from location to location, a phenomenon known as phoresy, in order to take advantage of flight to access a new food source. The Mites feed on carrion fly eggs and maggots, so phoresy is mutually advantageous to the Mites and the Burying Beetles. The Mites get a food source and the Burying Beetle benefits because more rotting flesh is available to its young.
I have seen other Sexton Beetles at the camp site since this one, and some were so heavily infested with mites it was a wonder they could fly at all.