Jul 142020

Thanks to everyone that responded to the Stag Beetle posts. My top favourite response came in an email from David, one of our best naturalists.

“I thought you might be interested to hear about something that happened to us a few days ago here in Meopham.  I was upstairs in my study at about nine o’ clock one morning when I heard a shriek from [my wife] downstairs. “Come quick, there’s something large and horrible in this basin”.  I rushed downstairs to our utility room to find [my wife] in one corner of the room gesticulating towards a basin on the work top which had a large black creature crawling about in it.  It was a female Stag Beetle, which I repatriated to a bush in the garden.  How or when it got indoors remains a mystery!”

Poor David, how embarrassing. But I know how you must of felt David! One can’t get fully trained staff these days.


Having said that,  Sally has found three stag beetles in the garden this year (to my none). The last one, a female,  she found floating in our garden pond. Sally fished it out but it must have been there for some time. She pronounced it dead. She then placed it on top of our wheelie bin  and left it there for me to look at. Several hours later I remembered to look and I was only just in time!. It was now starting to move and indeed it went on to make a full recovery! But before releasing it I noticed that it had red mites attached to its body just above the foreleg. I have seen this before, it makes me feel a bit itchy. I have always felt sorry for the beetle and have sometimes knocked some of the mites off. This time, I thought I would find out a bit more about the what the mites are doing. I was surprised by what I discovered. Its not what I thought.

The life cycle of the mite goes through several stages before becoming adult male and female. In particular, one of the stages is called a “deutonymph” which is able to attach itself to beetles. Not for feeding purposes but to be transported by the beetle to new places. They are hitchhikers or more scientifically “phoretic”. So when the deutonymph mites get to a new location (thanks to the beetle) they jump off and carry on their development to adults. Clever stuff! But it is even more clever than that. Apparently, female stag beetles have a “mycangium”, a microbe storage organ,  that contains a multitude of different species of fungi and bacteria.

These microbes are released at the egg laying site and are important agents in the breaking down of dead wood. So when the beetle eggs hatch, the dead wood has been pre- prepared to give the beetle larvae the food they need. The mites “know” this and, as they like the same conditions, they know its time to drop off. The beetles also carry species of nematode worms which appear to be doing something similar. I got all of this from a paper written about stag beetles in Japan. It concluded ” [stag] beetles can be regarded as transporters of their own microbial and microscopic invertebrate guilds that are associated with dead wood and slime flux“. Lovely phrase! So if we lose stag beetles we risk losing the community of microbes and invertebrates they contain. So give them some dead wood in your garden to get them started. Your garden needs a bit of slime flux!

Thanks to Sally for the photographs.


PS. Stag beetles are kept as pets in Japan. The authors of the paper were concerned that the pet trade imports foreign stag beetles.  If a beetle escaped that might be a problem. What the authors were concerned about though, was the potential risk of the release of all the others species that make up a stag beetle.



 Posted by on 14 July 2020 at 8:13 pm

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