Fig beetles (Cotinis mutabilis) are large, iridescent green insects often seen buzzing around gardens in the southwestern United States and Mexico. Sometimes called figeater beetles or green fruit beetles, they have clubbed antennae and can measure up to 1.3 inches long. Their distinctive, seemingly clumsy flight often leads to the misconception that these insects might be blind.
Fig Beetle Vision Explained
Despite their erratic flight patterns, fig beetles are not blind and have functional vision. Like many insects, they see through compound eyes, complex visual organs composed of numerous light-sensing units called ommatidia. Each ommatidium contains its own lens and light-sensitive cells, creating a mosaic view of their environment.
This vision is highly effective at detecting movement and changes in light intensity. While not as sharp as human eyes, it is perfectly suited for their daily activities. Their tendency to collide with objects during flight relates more to their flight mechanics, as they fly with partially open wing covers (elytra), rather than poor sight.
How Fig Beetles Use Their Sight
Fig beetles use their vision for several behaviors, though it is not their sole sensory input. They navigate their surroundings, identifying broad shapes and light cues that guide their flight paths. Their sight helps locate food sources, particularly ripe or fermenting fruits like figs, peaches, and grapes. Vision also helps them identify potential mates and avoid obstacles or predators. While chemicals from ripe fruit primarily attract them from a distance, vision likely helps pinpoint the exact location of the fruit upon closer approach and in maneuvering around it.
Beyond Vision: Other Fig Beetle Senses
Beyond vision, fig beetles rely on other senses. Their sense of smell, or olfaction, is acute and plays a primary role in long-distance food detection. These beetles are attracted to gases emitted by ripening and fermenting fruits, allowing them to locate food from a distance.
Their clubbed antennae are covered with sensory hairs (sensilla) that detect these airborne chemical cues. These antennae and other body hairs (setae) also provide a sense of touch, allowing them to explore surfaces and navigate close quarters. These senses work in concert, compensating for any visual limitations and ensuring their survival.