A Mite-y Beetle Observation in Austria - Observation of the Week, 7/13/21

Our Observation of the Day is this mite-covered Burying Beetle, seen in Austria by @karimstrohriegl!

Currently a student working on his Bachelor’s Degree in Biology at the University of Graz, Karim Strohriegl had the opportunity to visit Austria’s Thayatal National Park last month, on a trip organized by Österreichische Entomologische Gesellschaft (ÖEG), an entomological organization. “The goal,” he says, “was to collect and/or identify as many species as possible and provide a species list to the national park.”

A Lepidoptera expert installed a light trap and I was taking shots of all kinds of different insects. When photographing a burying beetle of the genus Nicrophorus I was surprised to see that it was full of Gamasina [mites]. I had never seen an insect with that many mites on it and was amazed learning that they had a phoretic relationship.

Yup, while it looks as though that beetle is being devoured by the mites, it actually flies around with some (although usually not that many!) on its body, hence Karim’s use of the term “phoretic”. Members of the genus Nicrophorus are commonly known as “burying beetles” in English and they do specialize in decomposing dead animals. Using their mandibles and secretions from their mouth and anus, they’ll chew up and preserve the carcass, which they feed to their larvae. 

However, other carrion eaters like flies often reach the carcass and lay eggs on it before the beetle gets there. That sets up a competition between fly maggots and beetle larvae, which is where the phoretic mites (who are using the beetle as transportation to the carcass) come in. Entomologist Joe Ballenger writes:

The beetles can take care of some of [the maggots], but not all of them. This is where those mites come in. Those mites are specialists on fly eggs, and hungrily devour the eggs and young larvae. This keeps the flies from stealing the food that the beetles need to rear their larvae.

This relationship has another aspect, though. The mites can’t feed on anything bigger than they are, so they need the beetles to raise the mite larvae. The mite larvae feed off the same secretions the mother beetles use to feed their babies.

Beetles, mites, and flies are, of course, awesome, but the study of bees is what Karim (above) is focused on. He’s working on a bee project run by Naturschutzbund Steiermark and says “My main goal is to learn everything about wild bees and to be able to ID as many different species as possible.” He’s started to compile photo resources for bee identification on his website and hopes it will have many more species by the end of the summer.  

Learning to identify bees is also one of the reasons he uses iNaturalist, in addition to getting ID help and having a public database for his observations. 

At least half of my knowledge identifying bees I got through iNaturalist and the interactions with other users like @johnascher or @robertzimmermann. I also would like to thank my University Professor Gernot Kunz (@gernotkunz), who I think is the biggest fan of iNaturalist and who brings hundreds of students every year to the platform. His photographs inspired me to get into macro photography and through that I am paying so much more attention to my surroundings. Now I can photograph the smallest of the small and it’s amazing to see how beautiful these little creatures are.

(Some quotes have been lightly edited for clarity and flow.)

- There are some pretty good (albeit gruesome) videos online showing Nicrophorus beetles doing their thing. Here’s one from National Geographic, another from the Smithsonian, and this awesome narration-free video with great larvae-feeding and metamorphosis footage.

- Hopefully this inspires you to set up some lights and participate in the worldwide National Moth Week starting July 17th! More information here.

- Another phamously phoretic (sorry, I couldn’t resist) arachnid is the pseudoscorpion, and @abhiapc’s photos of some was a recent Observation of the Week!

Posted by tiwane tiwane, July 13, 2021 23:03


Wonderful essay and photograph. I've photographed phoretic mites a few times and am delighted to learn more about them.

I put a dead rat out, hoping to photograph the insects that came it. It disappeared! ... Now I wonder if burying beetles where the culprits. I'm eager to try again.

Posted by elvapaulson 3 months ago (Flag)

A wonderful observation! Thanks so much for sharing, @karimstrohriegl !

Also, anyone that views @gernotkunz 's observations is also likely to be inspired to get into macrophotography. Such magnificence in the tiny universe. :)

Posted by sambiology 3 months ago (Flag)

Nice job Karim!!!

Posted by diegoalmendras 3 months ago (Flag)

Just want to point out that several words in this post are misspelled. "Phamous" was obviously intended, but what about "sourroundings", "larve", and "metamorophosis"?

Posted by fluffyinca 3 months ago (Flag)

Cringy cool observation!

Posted by amzapp 3 months ago (Flag)

This makes me itchy! Nice obs (:

Posted by biocowboy 3 months ago (Flag)

Amazing observation , well done :)

Posted by karthikeyaeco 3 months ago (Flag)

Nice Karim, the way to go!

Posted by btree 3 months ago (Flag)

Herzlichen Glückwunsch zu dieser tollen Beobachtung, Karim!

Posted by carnifex 3 months ago (Flag)

The beetle-mite-fly-story is indeed a fascinating one, and a textbook example of mutualism. The mites probably belong to the genus Poecilochirus, and there's emerging evidence that the association between Nicrophorus species on the one hand and Poecilochirus species on the other hand is much more specific than previously assumed, see https://doi.org/10.1101/2021.05.20.443311

Posted by jakob 3 months ago (Flag)

Good work Karim! Thank you!

Posted by susanhewitt 3 months ago (Flag)

I came across another mite-y one in Normandy a while back https://www.inaturalist.org/observations/33456114
I'm looking forward to reading more from your post (just quickly checking in). Thanks!

Posted by redrovertracy 3 months ago (Flag)


Posted by atrox77 3 months ago (Flag)

Very Amazing!...Had to look up "phoretic" and am glad for the Beetle that it is just a "taxi"..!

Posted by katharinab 3 months ago (Flag)

Great observation! Phoresy (greek for "being carried" refers to traveling on the body of another species. Phoretic mites travel on beetles (in this case) but also lots of other species, including inside the nostrils of hummingbirds! The "mutualism" between the Poecilochirus mite and Nicrophorus is currently under study. There is some evidence that it is facultative- beneficial to the beetle when flies are abundant, but less so when flies are scarce. There are observations of mites feeding on beetle eggs when fly eggs are unavailable, in which case it would be a parasite. Mites have piercing and sucking mouthparts and can feed on fly eggs as well as the carcass secretions. It's a fascinating interaction, and deserves a lot more study!

Posted by rick_williams 3 months ago (Flag)

Fantastic story and awesome photos! Well done!

Posted by walkingstick2 3 months ago (Flag)

Thanks for paper @jakob, and the extra details @rick_williams!

Posted by tiwane 3 months ago (Flag)

that post was from @rosemary_smith , who studies Nicrophorus. She has a project on iNat -
Carrion beetles of Western North America that folks can check out

Posted by rick_williams 3 months ago (Flag)

Yes it carries some mites but I took pictures of one last year carrying many more mites:) https://www.inaturalist.org/observations/64318054

Posted by splint 3 months ago (Flag)

Wow, thank you all so much! :-)

Posted by karimstrohriegl 3 months ago (Flag)

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