Bug o’the Week – Dung Beetle

Salutations, BugFans,

 

Sometimes, the secret of getting a good picture is “Right time, right place, right toys.”  The BugLady has been longing to do an episode on dung beetles – they’re amazing insects, and they live right here in Wisconsin, but clearly, she has not been in the right place at the right time, kicking over the right clods (first dictionary definition).  Thanks to BugFan Freda for pictures of an international dung beetle, which will stand in for Wisconsin species.

“Dung beetle” refers to beetles whose lives are intertwined with dung, but the term is not exclusively a taxonomic one.  True, most of its practitioners belong to the beetle family Scarabaeidae and the subfamily Scarabaeinae, but the name is also applied loosely to any beetle that makes its living in dung.  In Wisconsin, that includes a member of the Clown beetle family Histeridae and a member of the Water scavenger beetle family Hydrophilidae, who swims in dung, but whose relatives swim in water.

 

Researching the dung beetle is like researching a rock star.  There are True Facts, YouTube videos, Facebook, kids’ pages, and even a graphic novel or two!

 

Because they have Super Powers.

Like many scarabs, dung beetles are drab, stocky, and well-armored, some with a horn or an exaggerated “brow” that’s used in fighting, and with legs adapted for gripping, digging, and pushing.  They use their antennae to catch the scent of excrement.

 

Though they don’t especially like cold weather, dung beetles live in a variety of different habitats (deserts, grasslands, agricultural lands, and woodlands) on all continents but Antarctica.

 

Why are dung beetles dung beetles?  Because, as adults and as larvae, they eat and live, in and around animal droppings.  They prefer the droppings of herbivores and omnivores, which tend to be somewhat under-digested.  Adults eat the liquid portion, not the roughage, and the larvae feed on the solids.  Some species eat carnivore poop, fungi or decomposing fruits.  They don’t drink.

 

They meet and mate around dung.  Dung beetles are divided into three groups, depending on style – dwellers, tunnelers, and rollers.  Dwellers keep it simple – adults don’t excavate the soil or manipulate the dung, they just lay their eggs on top of a manure pile.  The larvae hatch and feed within the maturing manure pile, but the adults move to one that is fresher and wetter.

Tunnelers dig into the soil below a dung pat and make tunnels and egg chambers.  The male hauls bits of dung into the tunnels, and the female arranges them (it stays fresher underground) and lays eggs.  Both parents may stay in the manure with the larvae, and the male uses his headgear to defend his female, food and family from rival males with prolonged, underground pushing contests.  Tunnelers dodge some of the parasites and predators that find “dwellers.”

 

It’s the Rollers that most intrigue us.  An adult male locates a pile of good stuff (not too dry), breaks off some pieces, and compacts them, forming a ball.  This he offers to a female, and if she’s willing, they roll it away to a likely spot, watching as they go for rival beetles that may try to steal it (early naturalists thought that the other beetles were just helping the happy couple).

 

When they find a soft substrate, they bury the brood ball by hollowing out the space below it so it sinks into the ground.  After mating, the male leaves to sow his wild oats elsewhere, and the female makes a few more brood balls and lays a single egg in each, sealing them by smearing them with a paste of saliva, feces, and dung.  In some species, she stays to tend the grubs, which are described as “six legs and a mouth.”  She only lays a handful of eggs in her lifetime, and she works to ensure their survival!

 

Dung balls are also made and buried as food caches.

 

Dung beetles provide a variety of important ecological services (one of which is that without them we’d be knee-deep in, well,……).  They aerate the soil, recycle nutrients, improve water circulation, and disperse seeds, all of which encourages plant growth and improves conditions for grazing animals.  Fewer cow pats means less habitat for dung-loving, cow-biting flies (one cow pat can generate 3,000 flies).  And they break down and prepare the dung for species that will use it after they do.

DUNG BEETLE FUN FACTS

  • Instead of searching for their supper, some smaller species ride around on their suppliers and wait for a deposit to be made.

 

  • On the Great Plains, a wonderful owl called a Burrowing Owl (kind of the meerkat of owl species http://www.birdweb.org/birdweb/bigger_image.aspx?id=3889&type=p) collects the droppings of large grazers and places then around the entrance to its underground home.  Beetles find the dung and do their thing, and the owls have a steady supply of protein morsels.

 

  • A dung beetle may fly 30 miles to find dung, can roll a ball that weighs up to 10 times its weight, and can bury dung that is 250 times heavier than it is in a single night.

 

  • Dung beetles use celestial signals to chart a course from Point A to Point B.  Diurnal species roll their dung balls in a straight line, navigating by the sun (going around obstacles and then correcting).  Nocturnal species use polarized moonlight, and one species even uses the Milky Way to orient.

 

  • In various parts of Asia, dung beetles are used medicinally or are eaten.  In ancient Egyptian beliefs, the forming, transporting, and burying of a dung ball was a metaphor for the daily renewal of the sun.

 

Do dung beetles light your fire?  Find out more about them in this BBC Earth video by the venerable David Attenborough: https://www.youtube.com/watch?v=Zskz-iZcVyY,

 

And in this TED talk: https://www.mensaforkids.org/teach/ted-connections/dance-of-the-dung-beetle/,

 

and in this bulletin about dung beetles in Wisconsin: https://fyi.extension.wisc.edu/wbic/files/2016/08/Dung-Beetle-Ext-fact-sheet-final.pdf,

 

and in this article about the amazing dung beetle-nematode connection (it’s not gross – promise): https://www.theatlantic.com/science/archive/2018/10/dung-beetles-sexually-transmitted-worms/571804/.

 

Kate Redmond, The BugLady 

Bug of the Week archives:
http://uwm.edu/field-station/category/bug-of-the-week/