What can serve as a nose, ears, fingers, taste buds, weather station, smoke alarm, sugar-analyzer, communication center, speedometer, compass, and much more—all rolled into one?
It’s a pair of graceful, practical, and indispensable antennae, perfected many millions of years ago, and built right into the bee’s adult form.
Dancing in the Dark
A honey bee forager recruits her nest mates to find pollen or nectar in a particular patch of flowers by doing a “waggle dance” in the dark interior of the hive. How do other foragers learn where to go, how far to fly, and what to find there without actually seeing the performance?
They use their two antennae to hear, rather than to view the dance. The dancer’s waggling motion causes sound waves to travel through the air inside the hive, and these vibrations cause a specific degree of deflection of the antennae.
The sensation is transmitted from the tip of each antenna to a membrane in the middle section, called the Johnston’s Organ, which vibrates something like an eardrum and sends the data on to the bee’s brain for analysis and reaction. (This special organ can also detect electric and magnetic fields, and speed of flight, by the way.)
Further, the dancer carries molecules of floral fragrance along with pollen particles on her body, both of which the attentive audience can smell via chemical sensors, also located on the antennae. That’s not all! Once the foragers leave the hive and fly off to find the food source described in the dance, they gather information using their antennal sensors during the flight to find the destination and to evaluate the sweet reward before they land.
“OK, I found the flower, but where’s the nectar?”
Tactile hairs at the antennal tips detect textures, bumps, or other physical clues that tell them how to enter each different type of flower, which, along with visible dots and lines, lead the bees right to each blossom’s nectary.
Sensors by the Thousands
There are literally thousands of receptors of various types located mostly on the outermost segment of the three-part antennal structure that respond not only to sound, odors, and the taste and concentration of sugar, but also to touch, and to other physical parameters of the environment, such as gravity, temperature, humidity, carbon dioxide concentration, and wind speed, for example.
Just about everything the bee needs to know is discovered through these special sensory data-collection tools, and the bee constantly modifies its behavior according to the input.
The bee’s antenna has three sections: the segmented flagellum holds most of the sensors; it is attached to the short second section, the pedicel, by an elbow joint, which then attaches to the third section, the long, straight scape. The scape ends in a rounded end that fits in a bowl-like depression on the bee’s head, forming a classic “ball and socket joint” that lets the antenna rotate in all directions, controlled by a set of four muscles. (Diagram: Entomology for Students Blog)
Sensory receptors are classified by their shape and function:
- hairs for touch
- plates for chemical and light detection
- pits and pegs for chemoreception—that is, to identify tastes as well as smells, including the pheromones that make up the chemical language for bee communication.
Each worker antenna is estimated to have ~3000 chemoreceptors. The queen has about 1600, and the drone has 300,000 on each antenna. Drones rely on both sight and smell to detect virgin queens as they arrive in the mid-air drone aggregation area.
There’s a tuft of sensory hairs at the very tip of each antenna, and most of the smell receptors are toward the bottom end of the flagellum surface.
As Clean as a Whistle
Because the bee’s antennae are absolutely vital to the insect’s existence, they must be kept clean and functional. A special tool for that purpose is built into each of the front legs – isn’t that handy?! It consists of a set of bristles lining a joint that can be closed to perfectly wrap around one antenna and brush it clean as the bee draws it from base to tip through the circle of stiff hairs.
Life in the Unlighted Hive
Although you artificially bring light into the hive when you open it for inspection, remember that it is otherwise always dark in the interior, and therefore visual signals are not practical or useful.
You can observe that an important part of the bees’ communication is carried out by touching one another with their antennae, along with exchanging chemical and sound messages. It makes perfect sense in that environment!
Imagine how all the complex tasks of colony life are coordinated and carried out without benefit of sight:
- building wax comb, which requires detecting the precise dimensions of a cell under construction
- processing and packing pollen and nectar into cells; caring for eggs and brood as well as for the queen
- distributing water, food, and pheromones among all the colony members
- and on and on—a multitude of jobs and messages all requiring data taken in by sensors on the antennae.
Accordingly, the bee’s antennae are in constant motion, bringing in a continuous flow of data to guide every move and activity, and even the timing of certain physiological changes.
Even our smartest mobile phones can’t quite compare to these marvelous appendages, which must be among the most wonderful, handiest and dandiest gadgets Mother Nature ever created!