In the center of my back yard lies a failed attempt of a vegetable garden laid to waste by the combined efforts of several groundhogs, rabbits, and white-tailed deer. This rich organic plot is now passing through the broad-leafed weed stage of succession before it becomes a part of my hearty and drought resistant zoysia grass lawn. Last week on a sweltering morning I saw dozens of bumble-bee like insects zooming inches above the ground. As one of these rascals landed nearby, I was surprised to see not a bee but an elegant scarab that looked like a Japanese beetle on steroids.
The flight patterns and buzzing sounds of the Green June beetle are strongly reminiscent of a large bumble bee. Perhaps these behaviors are a clever way to ward off would-be predators that learned not to mess with buzzing, stinging insects. Green June beetles are part of a clan known as fruit and flower chafers or Cetoniinae. While most flying beetles spread their hard outer wings to fly, members of the Green June beetle clan simply lift their hardened outer wings like the hard top of a sports car and out pop the hind wings used for flight. Male beetles zoom in the morning as they search for mates. Females also fly low as they search for suitable places to deposit eggs in the soil. Once the female locates a favorable spot, she burrows several inches into the earth, makes a large sticky ball of soil and proteinaceous goop, and deposits eggs in it.
Eggs hatch in a few days into small c-shaped larvae known as white grubs. During the day the white grubs rest in a burrow underground, but at night they move to the surface of the earth to eat decaying organic matter. Soils with organic mulches and grass clippings like my miserable garden and farm fields that received applications of manure are highly attractive to the egg-laying females and may be loaded with grubs. Most of the damage caused by grubs results as they move to the surface of the soil to feed. Their burrows can be the diameter of your thumb and small mounds of soil often surround the burrows. The mounds and disruption caused by burrowing create problems on golf courses and in lawns. Although Green June beetle grubs have well developed legs on their thorax, legs are not the primary mode of locomotion when grubs are out of the soil. Each year a few Green June beetle larvae become stranded in my carport after a busy night of feasting. The grubs have a series of stout hairs on the upper surface of their back. To get around above ground the grub lies on its back and with undulating motions wriggles across the surface using its hairs for traction. After feeding for several months near the surface of the earth, the grub burrows deeper underground to escape winter's bitter cold. In spring as temperatures warm, larvae return to the upper strata of the soil to resume feeding and complete development. They form pupae and by the latter half of June and into July adults emerge to eat, mate, and lay eggs. Unlike their more destructive relatives, Japanese beetles, Green June beetles are not serious pests of roses, lindens, or other plants. Their primary foods are thin-skinned fruits such as berries and grapes. I have also observed several adults congregating to eat fermenting exudates from a wound on a tree. Fresh fruit and fermenting beverages sound just fine on a warm summer day. Maybe these Green June beetles are just a bit smarter than we think.
Much of the information for this Bug of the Week came from Daniel Potter’s excellent reference book “Destructive Turfgrass Pests”, Ann Arbor Press, and the interesting article “Mimicry of Hymenoptera by Beetles with Unconventional Flight” by R.E. Silberglied and T. Eisner.
To learn more about Green June beetles on line, you can visit the following web sites: