June bugs are a familiar sight during late spring and early summer evenings, often seen clumsily flying and bumping into various objects. These reddish-brown beetles, typically half an inch to an inch long, are part of the Phyllophaga genus. Their erratic flight against windows and porch lights is a common summertime occurrence. This behavior stems from their nocturnal habits and a biological response to light.
Nocturnal Instincts and Light Attraction
June bugs are nocturnal insects, active after sunset. They emerge from the soil as adults in late spring or early summer, primarily to mate and lay eggs. Like many other nocturnal insects, June bugs exhibit positive phototaxis, an attraction to light sources. This behavior is a navigational strategy.
Historically, the moon was the most consistent light source for nocturnal insect navigation. Insects use celestial bodies like the moon as a compass, maintaining a constant angular relationship to the distant light to fly in a straight line. This allows them to cover distances efficiently.
Disrupted Flight: The Mechanics of Crashing
The attraction to light, combined with a specific navigational technique, explains why June bugs crash. Many insects employ “transverse orientation” or “light compass reaction.” This involves keeping a distant light source, such as the moon, at a fixed angle to maintain a straight flight path. For instance, an insect might keep the moon consistently to its left to fly forward.
When a June bug encounters a close, artificial light source, this navigational system becomes disrupted. The angle to the nearby light changes rapidly as the insect moves, causing it to continuously reorient itself. This leads to a spiral flight path, drawing the insect closer to the light source, often resulting in collisions. Their robust bodies and less agile flight also contribute to their clumsy appearance when disoriented.
Why Artificial Lights Pose a Unique Challenge
Artificial lights present a unique challenge to June bugs and other nocturnal insects due to their proximity and light emission. Natural light sources like the moon are so far away that their light rays reach Earth as parallel lines. This allows insects to maintain a stable flight angle.
In contrast, artificial lights are close and emit divergent light rays. An insect attempting to maintain a constant angle to a nearby artificial light finds the angle constantly shifting. This forces the insect into a continuous attempt to correct its flight path, leading to erratic movements and unavoidable crashes into the light fixture or surrounding objects. This disorienting effect, rather than a simple attraction, is the primary reason June bugs crash into everything.