If an alien visitor were to ask how many species of animals we have here on Planet Earth, scientists would be hard-pressed to give a single number as an answer. There's still a lot of debate around the topic. We are constantly reorganizing animal classifications, lumping some species as one and splitting others into several. Accidental duplicates from different parts of the world are discovered, meaning two seemingly different species are actually only one. A well-accepted estimate is around 1.7 million species of animals. When contemplating the diversity of life it can be easy to forget that insects are animals, but they make up over half of the documented species with nearly 1 million types of insects! Scientists discover around 7,000 new species of insects every year! Their diversity in forms is astounding; we learn more and more about their lifestyles, adaptations, and capabilities every year. Beetles comprise the largest group of insects (Coleoptera) with 350,000-400,000 different species, making up an estimated 40% of the insects on earth and nearly 24% of the total animal species on earth. Here in North America, we have upwards of 30,000 species of beetles. Let’s look at some of the beetles that call Minnesota & Wisconsin home and take a deep dive into a few!
Check out the variety of beetles the HDT Staff & Bingo Scavenger Hunt Participants have found!
Fireflies
Is there anything more reminiscent of childhood innocence than frolicking through a field of fireflies? Perhaps you grew up calling them lightning bugs, moon bugs, blinkies, waawaatesi, or maybe even peenie-wallies! They have many names all over the world. Fireflies' bioluminescent glow is considered the most efficient source of light with 100% of the energy turning into light with nothing lost as heat. Many of us can conjure up a memory of flickering fireflies, but you might be surprised to learn that there are over 2,200 different types of fireflies around the world.
Fireflies, like all beetles, go through complete metamorphosis, meaning they have four stages in their life cycles: egg, larva, pupa, and adult. All fireflies glow as larvae and pupae, but only some glow as eggs or adults! They spend most of their time in the larval form, where they are voracious predators of soft-bodied invertebrates like snails, slugs, and worms. The firefly larvae inject a paralyzing neurotoxin into their prey with a bite, then hit them with digestive enzymes to liquefy their prey, and then slurp it up! They overwinter in their larval form and may spend 2-3 years as larvae before becoming an adult! Due to the mild winter we had last year and a very wet spring/early summer that favored firefly prey, this summer has had a booming firefly population.
Fireflies are split up into three different categories. Daytime dark fireflies fly during the day and the adults do not glow. They communicate with pheromones instead of lights. Glow-worm fireflies have adult females incapable of flight but produce a long-lasting glow to attract non-luminescent males. Flashing fireflies are what we typically think of, with each species having a unique flashing pattern of bright lights and/or swooping motions to communicate and attract a mate. To learn more about their glowing lights and how you can help, check out our previous blog "Fireflies Forever."
Fireflies also have lucibufagins - a distasteful steroid that helps deter predation from animals like birds or spiders. They can release some lucibufagins in foul-smelling droplets of blood when they’re frightened to prevent being eaten. Unfortunately, one group of flashing fireflies has lost their ability to produce lucibufigans, but don’t worry. They got creative. This group is called the “femme fatales.” Females in the femme fatales mimic the light signals of females from other species. When the males of that species come close, thinking they’re about to get lucky, the femme fatales snatch them and eat them, stealing their lucibufagins to amp up their own defense. How cool is that?!
Dung Beetles
One of our favorite things to find in nature when exploring is scat! This summer during Eco Camp here in the Driftless Region, we came across not just any scat – this scat was moving! A camper walked up to us with their hand out and asked the classic question “What is this?” just to be told they are holding a piece of deer poop. It almost looked like two pieces of scat, but upon closer examination, we realized that there was a dung beetle as well!
It was a memorable moment not just for the campers, but for us camp counselors as well. We made it our goal to find more beetles. Searching the same area our camper had found this beetle, we not only found more dung beetles, but we also found the main dung pile! Most people don’t get too excited over a pile of deer poop, but we were thrilled. There were a lot of dung beetles grabbing pieces of the poo and rolling it away somewhere more secretive, as well as dung beetles mating near the pile. The poo is where all the action was!
Video taken at the Trempealeau National Wildlife Refuge showing a dung beetle with deer scat.
There are a few different categories of dung beetles; rollers, tunnelers, & dwellers. The
ones we came across fell into the roller category, and are the most fun to watch as they take their piece of scat from the main pile to a different location to bury. Tunnelers will dig a tunnel underneath the dung for their larvae – their tunnels can be several feet long! Dwellers make the dung pile their home base, living out their entire life cycle in the scat. All types of dung beetles play an important role in our ecosystem as decomposers, cleaning up ‘gross’ things others wouldn't want to touch!
Dung beetles strike a pose before continuing on their way with their dung ball.
Whirligig Beetles
Watch them too long and you may start feeling dizzy: whirligig beetles couldn’t have a more perfect name! These beetles swim on the water surface in groups in an erratic pattern, avoiding collisions by sensing the ripples and making fast reactions. They occasionally dive under the surface if threatened by a predator and take a little air bubble down with them. The bubble will be tucked under their wings near the end of their abdomen since they breathe through a series of openings located on their rear end.
That is not the only wacky adaptation these beetles have, they also have specialized eyes to help them see underneath the water as well as above them at the same time! They have split compound eyes, making it look like they have 4 eyes. Having a pair looking up at the surface can help them hide from predators like birds, and the pair of eyes that are submerged can keep watch on any fish looking for a snack!
Whirligigs are opportunistic scavengers meaning they will eat anything that comes across their path. From aquatic larvae to insects that have fallen into the water, no invertebrate is safe from them! They will occasionally eat dead creatures too that have fallen in or near the water. Even larvae whirligig are carnivores.
iNaturalist user Hannah Girgente found a whirligig larva & Dianne Robinson found quite the swarm!
They spend most of their life cycle in the water, only leaving as an adult if searching for water & as a larva hatching. Adults lay their eggs on the underside of aquatic plant leaves and once the larva emerges it will feed on other invertebrates until it crawls from the water to pupate into an adult, then returning back to the water.
Blister Beetles
Blister beetles are a group of medium-sized insects that have a very unique characteristic about them. If bothered by a threat, they can secrete a chemical substance from their bodies. This chemical is cantharidin which can cause blisters in humans and is poisonous to both humans & animals.
One species of blister beetle is known as the Oil Beetle, which gets its name from the oil-like substance it emits when threatened. It has good reason to do so, as this species does not have wings! Rather their wing covers (known as the elytra) cover just a portion of their wings, compared to most beetles whose wings and elytra cover their whole abdomen.
Left: iNaturalist user Eric Squig found out what oil beetles are capable of doing. It's important to remember to not handle things in nature that you are unsure of - you never know what could harm you! Right: Two oil beetles mating spotted by user ludiviksmith, the female is the larger one on the bottom and the male is the smaller beetle on top.
This species has a unique and complex life cycle known as hypermetamorphosis. As a larva, it has several different stages with different body types & functions. These stages, known as instars, range from starting as a triungulin catching a ride on a bee to being a couch potato in a bee’s nest feasting on all the bee larvae. To discover more about this phenomenon check out this YouTube video from the BBC about blister beetles in the desert! Once they emerge as adults, they stray away from the insectivorous and parasitic behavior they once had and feed on plants instead.
Conclusion
With roughly 40% of insects being in the beetle family, it’s no surprise that they can range in looks so drastically and can be found in almost every habitat around us. Some may twinkle in the night sky like fireflies, while others may leak a chemical onto your skin when threatened! It is amazing how diverse beetles can be, and they play such an important role in our ecosystem. From helping pollinate plants to decomposing dung, we have a lot to thank beetles for. Beetles forever!
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