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Blane Klemek: The hum of hundreds of flying June beetles

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On a recent June night, after enjoying a campfire in my backyard, it came time to head back to the house. As I strolled across the lawn, the cool black calm of nightfall compelled me to stop and listen to the sounds of gray tree frogs. It was a beautiful night. I also became aware of being surrounded by June beetles in flight. They were virtually everywhere my ears could hear as they emerged from their underground pupae.

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The experience was nothing short of amazing. The hum of hundreds of flying June beetles, their buzzing wings whirring through the still air, was an audible spectacle to be sure. Some of the beetles came within inches of my head as they sped past, while others were aloft at greater heights. Some were landing in the tall grasses and trees, while others sounded as if they were crash-landing and smashing into various objects. There seemed to be a sense of urgency to it all, yet none of the beetles were going in any particular direction.  

June beetles belong to a large family of beetles, Scarabaeidae, which are included in the impressive order Coleoptera. The genus, Phyllophaga, includes many species. And though most people refer to June beetles as June bugs, the insect is not a bug at all. Bugs have sucking, or piercing, mouthparts, whereas beetles have chewing mouthparts.

Another major difference between bugs and beetles are found in each of the groups’ wings. Beetle wings are contained underneath hard shells, or elytra as these shells are called. The hind wings, which are membranous and folded underneath the elytra, are not visible until the beetle prepares to fly. At such time, beetles open their elytra to expose their hind wings and accomplish flight. Bug wings, on the other hand, if they have wings, have no covering, and are usually membranous.

Other differences between bugs and beetles can be observed at their respective stages of development. Bugs undergo incomplete metamorphosis, where juveniles resemble adults, are smaller and have no wings. In contrast, beetles undergo complete metamorphosis such as what butterflies and dragonflies go through. Beetle larvae are worm-like grubs with hardened heads, chewing mouthparts and legs.

And such is the life of the June beetle. Their entire life cycle, depending on the species, can be as short as one year and up to four. After eggs are laid in the ground by adult beetles, larvae soon hatch from the eggs. Larval June beetles can live as long as three years before surfacing to become the adult form that most of us are familiar with. Emerging from the ground as fully developed adults on warm spring or summer nights, June beetles begin to seek mates almost immediately.

Adult June beetles appear black in color, but are actually reddish-brown. At about a ½-inch to 5/8-inches long, June beetles are fairly large in size as insects go. Ask anyone who has experienced a collision with a June beetle while riding a motorcycle and they’ll tell you that June beetles can hurt.

As most people know, June beetles are attracted to lights. During large flights, it’s not uncommon to have tens of dozens of beetles banging relentlessly into the windows and screen-doors of our homes on those nights when the beetles emerge. Apparently, females, for whatever reason, are less attracted to lights. Perhaps their main intent is to lay eggs, which of course is what they seek to do.

If you observe these fascinating insects long enough, you will eventually discover that females are the beetles that dig into the ground. They’ll dig up to five inches below the surface to deposit their eggs, at which point she exits, leaving her eggs to develop on their own, and resumes her short life by feeding on the leaves of trees at night and resting during the day.

Three to four weeks later the C-shaped, white-colored grubs hatch and begin their three-part larval development. The first two stages, or “instars” as each of the stages are also called, lasts approximately three weeks each. The third stage lasts the longest.

The larval June beetle’s third and last instar continues inside the earth throughout the summer and autumn until the following spring. And, as many of you have come to expect, adult June beetles begin emerging in late spring and early summer. Prior to the adults’ emergence, larval June beetles pupate some three to six-inches deep in the soil where they remain for another three or so weeks until, at last, when conditions are right, the adult beetles appear en masse.

June beetle larvae — those white grubs with hard heads and odd-looking legs—are eating machines as they grow and develop. In some extreme cases, June beetle larvae can destroy lawns through their feeding and tunneling activities on the roots of grasses. In such instances, whole lawns can turn brown and not green-up at all the following spring. Also, in case you have ever wondered, June beetle larvae are what mammals like skunks are often digging for in people’s lawns. Skunks love eating these juicy, nutritious grubs.

Indeed, another annual natural event has come and gone. These night-flying insects that some people call bugs, but are really beetles, are out and about every year around this time. Their appearance, which lasts for only a short while, will assure that, once again, more June beetles will emerge next spring as we get out and enjoy the great outdoors.

BLANE KLEMEK is a Minnesota DNR wildlife manager. He can be reached at bklemek@ yahoo.com.

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