Japanese beetles and June bugs are often confused, but they are distinct pests belonging to the scarab beetle family (Scarabaeidae). They cause different types of damage and require separate management strategies. The Japanese beetle (Popillia japonica) is an invasive species, while the June bug often refers to native species in the genus Phyllophaga. Understanding the differences in their appearance, life cycle, and feeding habits is the first step toward effective pest control.
Physical Characteristics and Identification
The easiest way to distinguish between the two beetles is by examining their size and coloration. The Japanese beetle is a relatively small insect, measuring approximately 3/8 to 1/2 inch long. It is characterized by a bright, metallic-green head and thorax. Its hardened outer wings, called the elytra, are a distinct coppery-bronze color. A defining feature is the presence of five or six small tufts of white hair along each side of its abdomen.
In contrast, June bugs or May beetles (Phyllophaga spp.) are noticeably larger, typically ranging from 1/2 inch up to a full inch in length. These beetles have a duller appearance, usually a uniform reddish-brown or dark brown color. They lack the bright metallic sheen and the distinctive white hair tufts of the Japanese beetle. While some June bug relatives, like the Green June Beetle, are metallic, the most common Phyllophaga species are plain brown, making them visually distinct from the iridescent Japanese beetle.
Distinct Life Cycles and Activity Patterns
These two scarab beetles operate on significantly different seasonal and daily schedules. The Japanese beetle has a predictable life cycle that typically lasts only one year. Adults emerge in late June or early July and remain active for about four to six weeks. Adult Japanese beetles are diurnal, meaning they are active during the day, feeding openly on plants in direct sunlight. Grubs spend nearly 10 months underground, feeding on grass roots before pupating in the spring.
June bugs (Phyllophaga species) generally have a longer life cycle that can take anywhere from one to four years to complete, with many common species requiring three years. Adult June bugs emerge slightly earlier, usually in late May or June, but they are primarily nocturnal flyers. They are attracted to porch and street lights after dusk, conducting their mating and feeding flights then. Due to this multi-year cycle, the larval stage, or grub, spends much more time developing underground than the Japanese beetle grub.
Varying Damage and Control Methods
The feeding habits of the adult beetles determine the kind of damage they inflict on plants. Adult Japanese beetles are notorious for skeletonizing leaves, chewing the tissue between the veins and leaving behind a lace-like structure. Their feeding is concentrated above ground on flowers, ornamentals, and fruit trees, often occurring in large aggregations. Control for the adult stage often involves hand-picking beetles into soapy water, particularly in the morning when they are less active, or using foliar insecticides.
Conversely, adult June bugs cause only minor damage to the foliage of trees and shrubs during their short flight period. The most significant destruction comes from their grubs, which feed heavily on the roots of turfgrass for multiple years. This root feeding can lead to large, irregular dead patches of lawn that can be lifted easily, similar to rolling back a piece of carpet. Control measures focus on treating the soil to eliminate the grubs using systemic insecticides applied preventively, or applying biological controls such as parasitic nematodes.