June beetles, often called May beetles or May/June bugs, belong to the large genus Phyllophaga, encompassing hundreds of species across North America. These heavy-bodied scarab beetles typically range from a half-inch to one inch in length. They have a robust, oval shape and are generally a reddish-brown to dark brown color, often with shiny wing covers. The adults emerge from the soil in late spring and early summer, earning them their common names. They are nocturnal insects whose clumsy flight patterns are often noticed as they are attracted to outdoor lights after sunset.
Ecological Status of June Beetles
The question of whether June beetles are invasive stems from the significant nuisance and damage they cause, but the most common species of Phyllophaga are native to North America. An invasive species is defined as one that is non-native to the ecosystem and whose introduction causes or is likely to cause economic or environmental harm. June beetles are endemic and established parts of the native ecosystem, meaning they do not fit this definition. While they are considered pests, their native status ensures they have natural predators and diseases that help regulate their populations. The term “pest” simply describes any organism that is destructive to crops, livestock, or otherwise a nuisance to humans. Therefore, June beetles are classified as native pests, not invasive ones.
The Cycle of Damage Caused by June Beetle Grubs
The primary source of damage comes from the larval stage, which is spent entirely underground. Females lay 50 to 200 pearl-like eggs in the soil during early summer. These hatch into white grubs, which are soft, white, and curled into a distinct C-shape with a brown head capsule.
These grubs are voracious eaters, feeding primarily on the roots of grasses and other plants. The June beetle life cycle is prolonged, often taking two to three years for the larvae to fully develop before emerging as adults. This extended subterranean phase allows grub populations to build up over multiple seasons, leading to cumulative damage.
The grubs’ feeding activity severs the roots from the turf, disrupting the plant’s ability to absorb water and nutrients. This results in patches of dead or thinning grass that first appear yellow and then turn brown. A clear sign of infestation is the ability to easily peel back sections of the turf like a rug, as the root structure has been consumed.
A secondary form of damage is caused by small mammals seeking out the grubs as a food source. Animals such as skunks, raccoons, and moles will dig through the lawn to access the protein-rich grubs. This foraging activity results in irregular, torn-up sections of turf that often present the first visible sign of a substantial grub population.
Distinguishing June Beetles From Invasive Look-alikes
June beetles are frequently mistaken for the much more destructive and invasive Japanese beetle (Popillia japonica). Distinguishing between the two relies on observing their physical appearance and daily behavior.
The native June beetle is generally larger (up to an inch long) and has a dull, uniform brown or reddish-brown coloration. The invasive Japanese beetle is noticeably smaller (less than half an inch) and features a striking metallic green head and thorax, with coppery-bronze wing covers.
A specific identifying feature of the Japanese beetle is the presence of five patches of white hair tufts along each side of the abdomen, which the June beetle lacks.
Behavioral differences are also key. June beetles are strictly nocturnal, flying clumsily at night and congregating around lights. Conversely, Japanese beetles are diurnal, meaning they are active during the day and feed aggressively on the foliage of ornamental plants and fruit trees.