June bugs, also known as May beetles, are large, buzzing insects whose sudden appearance in late spring and early summer is a predictable sign of the season in North America. Their clumsy, heavy-bodied flight and nocturnal habits make them noticeable. Understanding their existence requires exploring the unique biology that governs their synchronized emergence and their function within the natural world.
Identity and Classification
June bugs belong to the large genus Phyllophaga, part of the Scarabaeidae family, or scarab beetles. The genus name is derived from Greek words meaning “leaf eater,” referencing the adults’ feeding habits. With over 900 species across North and South America, these beetles are a diverse group.
The adult beetles are typically reddish-brown or mahogany-colored, ranging from 12 to 35 millimeters in length. Their heavy bodies and hard, protective wing covers, known as elytra, contribute to their characteristic clumsy flight pattern and loud buzzing sound. While they are often mistaken for other scarabs, Phyllophaga species present a more uniform color and lack the metallic green or coppery-brown markings of the Japanese beetle.
The Three-Year Cycle of Emergence
The June bug’s prolonged life cycle dictates the timing of their massive seasonal emergence. These beetles undergo a complete metamorphosis, moving through four distinct stages: egg, larva, pupa, and adult. This lengthy developmental schedule provides the primary explanation for why the insects appear so suddenly and in such large numbers.
A female beetle typically buries 50 to 200 eggs deep in the soil during late spring or early summer. These eggs hatch into the larval stage, commonly known as white grubs, which are C-shaped, whitish with a brown head, and grow up to 40 millimeters long. The grub stage is the longest and most impactful phase of the beetle’s life, lasting one to three years underground.
During this extensive subterranean period, the grubs feed voraciously on the roots of grasses and other plants. The duration of this feeding time, which varies by species and climate, synchronizes their adult emergence. This means that adults from the same cohort mature and emerge simultaneously in late May and June to mate. Once mature, the grubs enter the pupal stage, transform into the adult form, and then dig their way to the surface, ready to start the cycle anew.
June Bugs’ Role in the Ecosystem
June bugs fulfill several important functions that contribute to the balance of their natural habitats. Both the larvae and adults provide a food source for a wide array of wildlife.
Food Source
Birds like crows and robins actively hunt the grubs in the soil, while nocturnal mammals such as skunks, raccoons, and moles readily dig up the larvae for sustenance. Adult beetles are prey for bats, frogs, and various insectivores. The grubs also serve as hosts for parasitic insects, including certain wasp and fly species. For example, the waved light fly lays an egg on the adult beetle, which then consumes the host.
Soil Health
While spending their years underground, the grubs contribute to soil health through their movement and feeding. As the larvae tunnel through the dirt, they help aerate the soil, which improves water penetration and benefits plant root growth. Furthermore, by consuming organic matter and decaying plant material, the grubs assist in nutrient cycling, returning valuable compounds to the soil for future plant use.
Interaction with Human Environments
The June bug’s life cycle frequently brings it into direct conflict with human interests, leading to its perception as a pest. The most significant damage is caused by the grubs as they feed on the root systems of turf and crops. This root destruction can lead to large, irregular patches of dead grass that can be easily rolled back like a rug, a clear sign of a heavy infestation.
Adult beetles also cause noticeable harm, though typically less severe than the grubs, by feeding on the foliage of trees and shrubs at night. They are known to target the leaves of species like oak, walnut, and maple. While they can cause defoliation, healthy trees usually tolerate the damage. Their strong attraction to artificial light sources after dark, known as positive phototaxis, causes them to swarm around porch lights and windows, resulting in clumsy, buzzing collisions.