The June bug, often called the May beetle, refers to hundreds of species within the genus Phyllophaga, meaning “leaf eater.” This reddish-brown scarab beetle is a common sight during warm late-spring evenings, characterized by its clumsy flight and attraction to lights. When the adult beetles vanish from the summer landscape, they retreat to a hidden, subterranean existence that allows them to survive the cold.
Understanding the Multi-Year Life Stages
The June bug’s seasonal absence is directly related to its complex, multi-year life cycle, which involves four distinct stages. The entire process from egg to adult often spans between one and four years, depending on the species and the climate. Most of this extended duration is spent entirely out of sight, deep within the soil beneath lawns and gardens.
The insect progresses through the egg, larva, pupa, and adult stages. The vast majority of its existence occurs in the larval form, commonly known as a white grub. This C-shaped, creamy-white creature feeds on the roots of grasses and other plants. Because the life cycles of different broods often overlap, the population below ground is significantly larger than the population of beetles observed flying above.
Overwintering Location and Dormancy
The June bug’s winter whereabouts are determined by the white grub, which is the stage that exclusively survives the cold months. As soil temperatures drop in the autumn, the grubs receive an environmental signal to prepare for winter survival. They actively burrow downward, migrating far below the topsoil layer where they feed during warmer periods.
This movement is a mechanism to avoid lethal freezing temperatures. Grubs typically descend well below the frost line, often reaching depths of 6 to 18 inches, and sometimes as deep as 1.5 meters (nearly five feet) in colder regions. At this stable depth, the grub enters a physiological state of dormancy known as diapause.
During diapause, the grub’s metabolic rate is drastically reduced, allowing it to conserve energy when no food is available. This lowered activity is comparable to hibernation and enables the grub to survive months of freezing surface conditions. The soil itself acts as a powerful insulator, maintaining a temperature gradient that prevents the grub from freezing solid.
Spring Thaw and Adult Emergence
The end of winter is signaled by the gradual warming of the soil, which triggers the grubs to become active again. Once soil temperatures reach a certain threshold, often around 70°F, the grubs begin to ascend toward the surface to resume feeding on plant roots. This ascent is the final preparation phase before their transformation into adult beetles.
After a period of feeding near the surface, the fully grown grub constructs a protective chamber of soil and enters the pupal stage, typically a few inches below the ground. Within this earthen cell, the grub undergoes a complete metamorphosis, transforming into the adult beetle. The adult remains inside the pupal chamber until the environmental conditions are ideal for emergence.
The adult beetles break out of the soil in late May or early June, which is the reason for their common name. They emerge for a brief, active period of mating and feeding on foliage, completing the multi-year cycle that began when the female laid her eggs. Their appearance above ground is the culmination of the grubs’ successful overwintering beneath the earth.