It is common for people to wonder about the relationship between the buzzing June bug and the C-shaped grub worm found beneath the soil. These two distinct forms are not separate creatures, but rather different life stages of the same insect. Understanding this connection clarifies a popular misconception about these widespread beetles.
The Adult June Bug
The adult June bug, also known as a May beetle, is a scarab beetle typically measuring 1/2 to 1 inch in length. Its body is thick and oval-shaped, often reddish-brown, though some species can be dark green. These beetles possess a shiny, hard shell and noticeable wings for flight.
Adult June bugs are primarily nocturnal, active during evening and nighttime hours. They are frequently observed clumsily flying around outdoor lights, often bumping into objects, as they are strongly attracted to artificial light sources. Their active period generally aligns with the warmer months, emerging in late May or early June and receding by late August or early September. Adult June bugs primarily feed on the foliage of trees and shrubs, including oak, walnut, maple, apple, and peach, and they may also consume flowers and fruits.
The Larval Grub Worm
Before becoming an adult June bug, the insect is a larval stage commonly known as a grub worm. These grubs have C-shaped, soft, white or cream-colored bodies, often with a brownish head and six small legs. Grub worms measure from 3/4 inch to 2 inches in length.
They reside underground in the soil of lawns, gardens, and agricultural fields, usually preferring moist, well-drained conditions. Their primary diet consists of plant roots, particularly grass roots, but they also consume decaying organic matter in the soil. Due to their root-feeding habits, grub worms are often considered garden pests, as their activity can lead to damaged lawns with brown patches.
The June Bug Life Cycle
The transformation from a grub worm to an adult June bug involves complete metamorphosis, a process with four distinct stages: egg, larva, pupa, and adult. The cycle begins when female June bugs emerge in late spring or early summer, burrowing 2 to 5 inches deep into the soil to lay their eggs. These tiny, white, oval-shaped eggs usually hatch into larvae (grub worms) within two to four weeks, often around 18 days.
The larval stage (grub worm phase) is the longest part of the June bug’s life cycle, with most species spending one to three years, sometimes up to four years, underground. During this time, the grubs grow through three developmental stages (instars), continually feeding on plant roots. The second year of larval development often causes the most significant damage to plants and lawns due to their increased size and feeding. As temperatures drop in the fall, the grubs burrow deeper into the soil to overwinter, becoming less active until spring.
Once the grub worm has completed its growth, it enters the pupal stage, in the spring or early summer of its final year. During this period, which lasts about three weeks, the grub undergoes a transformation within a protective chamber in the soil, developing into the adult beetle. Finally, the adult June bugs emerge from the soil, usually in late May or June, to mate and lay eggs, restarting the entire cycle. Adult June bugs have a relatively short lifespan, living for one to two months above ground.