Junebugs, a common sight during early summer evenings, are diverse beetles primarily belonging to the Phyllophaga genus. Known across North America as May or June beetles, their popular name stems from their emergence as adults in late spring or early summer. While their clumsy flight and attraction to lights can be a nuisance, understanding their biology reveals a complex life cycle.
Identifying Junebugs and Their Life Cycle
Adult junebugs are stout-bodied beetles, typically 0.5 to 1 inch long, though some can reach up to 1.38 inches. Their coloration varies from reddish-brown to dark brown, and some species may exhibit a metallic or iridescent sheen. They possess robust, oval-shaped bodies with shiny wing covers, known as elytra, which protect their hindwings. A distinguishing feature is their clubbed antennae, often about half the length of their bodies.
Junebugs undergo complete metamorphosis, progressing through four distinct stages: egg, larva, pupa, and adult. Females lay 50 to 200 pearl-like eggs in the soil, usually 2 to 5 inches deep, during midsummer, which hatch into larvae, commonly called white grubs, within 2.5 to 4 weeks. The larvae are C-shaped, cream-colored with a brown head, and grow from 0.75 to 2 inches long. This larval stage, which can last from 10 months to three years, involves feeding on plant roots and undergoing three molts. Grubs typically overwinter deep in the soil and are most destructive during their second year.
After the larval stage, grubs enter the pupal stage, transforming into adult beetles while still underground. This pupation lasts about three weeks. Adult junebugs emerge from the soil in late May or early June. They are primarily nocturnal, active after dusk, and strongly attracted to artificial light sources. This attraction is attributed to their use of natural light, like the moon, for navigation; artificial lights can disorient them, causing them to fly erratically towards the source. Adults have a relatively short lifespan, typically a few weeks to several months, during which their main purpose is to mate and lay eggs.
Junebugs: Impact and Management
Junebugs have practical implications, particularly due to their larval stage. White grubs feed on plant roots, leading to significant damage in lawns, causing brown patches and a spongy turf. In severe infestations, root damage can be extensive enough that sections of sod can be easily rolled back like a carpet. Grubs also consume roots of various other plants, including vegetables like potatoes and carrots, as well as ornamental plants and agricultural crops. Their presence can attract animals such as moles, skunks, and birds, which dig up lawns in search of this food source.
Adult junebugs primarily feed on the foliage of trees and shrubs, including fruit trees, though this damage is minor compared to the root damage inflicted by their larval stage. Managing junebug populations often focuses on non-chemical strategies. Maintaining a healthy lawn through proper cultural practices helps reduce their impact, including watering deeply but infrequently to encourage deep root growth and setting lawn mower blades higher. Physical removal methods include handpicking grubs during gardening or tilling the soil after harvest to expose grubs and eggs to predators. For adult junebugs, reducing outdoor lighting during peak emergence times or switching to yellow or sodium vapor lights can minimize their presence around homes. Re-seeding damaged areas of the lawn can help with recovery.