A wasp’s survival depends heavily on a highly developed sense of smell, or olfaction. This chemical detection system allows the insect to perceive airborne molecules in its environment, interpreting them to make decisions about finding food, avoiding danger, and locating its home.
The Wasp’s Olfactory System
The primary sensory structures responsible for olfaction are the antennae, which are covered in thousands of tiny, hair-like projections called sensilla. These sensilla act as pores that allow odor molecules from the air to enter and make contact with specialized sensory neurons inside.
Once an airborne odor molecule enters the sensillum, it is first captured by an Odorant Binding Protein (OBP) within the fluid-filled cavity. The OBP’s function is to solubilize the hydrophobic odorant and carry it across the aqueous lymph to the surface of the sensory neuron. The molecule then binds to a specific Odorant Receptor (OR) embedded in the neuron’s membrane, much like a key fitting into a lock.
This binding event triggers an electrical change in the neuron. This electrical signal is then transmitted to the antennal lobe in the wasp’s brain, where the information is processed to identify the specific odor.
Smelling Food and Finding Home
Wasps rely on their refined sense of smell to locate nutrient sources over long distances, primarily by detecting Volatile Organic Compounds (VOCs) released by potential food. For social wasps like yellowjackets, this involves tracking scents associated with both their adult sugar diet and the protein needed for their larvae. Adult wasps are attracted to sweet foods that emit fermentation products such as acetic acid and isobutanol, which are commonly found in ripening or decaying fruit.
The search for protein guides wasps toward the VOCs associated with other insects or carrion. Researchers have found that various aliphatic butyrates, such as heptyl butyrate and octyl butyrate, are effective at attracting common wasp species like Vespula vulgaris. These compounds, which are often used in synthetic lures, mimic the natural odors of their prey or protein-rich sources.
Olfaction also plays a role in navigation and homing, especially for social wasps that nest underground or in cavities. Workers returning to the nest are guided by a chemical cue that accumulates around the nest entrance. This cue is not an intentionally applied signal but rather an aggregation of hydrocarbons and other substances deposited from the legs and feet of hundreds of workers as they track in and out of the entrance. This collective scent trail helps foragers quickly locate the inconspicuous opening of their home.
Communication Through Scents
Within the colony, wasps use scents for complex social communication, primarily through the release and detection of pheromones. These chemical signals regulate numerous behaviors, from reproduction to defense, ensuring the colony functions as a coordinated unit. For instance, queen pheromones help maintain the colony’s social order by signaling her reproductive status and suppressing the egg-laying ability of worker females.
Pheromones are also used to mobilize a collective defense, a phenomenon known as the alarm signal. When a nest is disturbed or threatened, a defensive wasp may release specific volatile chemicals, sometimes from its venom sac, which instantly alert nearby nestmates to the danger. Compounds such as 2-pentanol and isoamyl alcohol have been identified as components of these attack pheromones in some species, triggering aggressive and coordinated defensive behavior in the colony.
The ability to recognize nestmates is also chemically mediated, often through a blend of Cuticular Hydrocarbons (CHCs) coating the wasp’s exoskeleton. Every colony possesses a unique scent profile, and the workers use their antennae to “smell” the CHC signature of any individual attempting to enter the nest. Wasps with a non-nestmate CHC profile are typically identified as intruders and aggressively attacked or rejected.