Other ways bees communicate and navigate
Pheromone Communication Honey bees communicate in a variety of ways. However, like so many other species in the natural world, communication through the interchange of volatile chemical signaling is the most predominant and robust method used. Pheromones are very often extremely volatile compounds or cocktails that are excreted by one member of a particular species and affect the behavior (“release pheromone”) or the physiology (“primer pheromone”) of another member of the same species. In honey bees there are many pheromones that govern and coordinate the activities of the hive. The most prominent pheromones (but by no means the only) are:
Queen Pheromone – This first and foremost primer pheromone known in nature is a five chemical cocktail produced in the mandibular glands of the queen bee. The queen pheromone actively suppresses the egg maturation process in the non-reproductive worker caste. It also has a variety of releaser pheromone functions, such as preventing queen cell construction, enabling worker cohesion during swarming, promoting collection of food and guiding the males to the virgin queen in its mating flight.
Nasanov Pheromone – Bees have an innate preference for sweet citrus-like smelling monoterpines. One of the reasons for this is the secreted components of the Nasanov gland located on the bee’s posterior abdomen. When seeking a new nest, when signaling the new queen the way home from a mating flight, or when signaling displaced bees the way back to the hive, the Nasanov gland is exposed and the bees fan their wings to create a scented airborne trail. This citrus-smelling trail is picked up in a homing manner and often elicits similar behavior in a nest-returning bee that has located the hive entrance.
Brood Pheromone – The cry of a baby elicits feeding behavior in mothers across the animal kingdom. Although bees cannot scream or hear, when larvae are in open cells, they excrete chemicals that elicit feeding behavior in nursing bees. Young larvae are fed the excretion of the nurse bees’ feeding glands, whereas older larvae are fed bee-bread.
Alarm Pheromone – Most humans fear bees because of their stinging – the pain, the swelling, the itching and the dreaded consequences of anaphylactic shock for those who are hyper-allergic. Yet, for the honey bee, stinging is a suicidal action because of the dissociation of its digestion system. Such an action is hardly useful if it does not lead to the fleeing of the person or animal that threatened the hive. Prior to stinging the guard will try to ward off the threat by typical “harass” flights that say “don’t mess with me!” But often, the temptation of the honey is too much for the assailant to pass by, and the bees must coordinate an efficient attack. They do so by the unique blend of chemicals that is released from the dufour glands located in close proximity to the sting apparatus. This alarm pheromone elicits stinging behavior in other individuals of the hive in order to increase the attack’s efficacy.
Karl Von Frisch received the Nobel Prize for discovering one of the most difficult to fathom complexities of honey bee behavior… they talk to each other abstractly. Most people would surely put abstract language as one of the top three qualities that define human singularity. But, on a conceptual level, language in general and abstract language in particular, evolved as we became more organized in larger communities. Language dialects define groups, and this has resulted in the explosion of cultural and technological evolution.
How appropriate then that the few species of eusocial honey bees, unlike any of the other tens of thousands of solitary bee species, became the first group to have its language deciphered. Moreover, different races of bees were found to have different dialects that are incomprehensible to non-native species. The primary benefit of language evolution in humans was surely more efficient gathering of food resources. Likewise, bees use the “Figure 8 Dance” in colony mobilization to communicate the quality, direction and distance of a food source.
Honey bees navigate accurately and repeatedly to food sources, as well as communicate to their colony members the distance and direction in which to fly to reach them. This information is conveyed in the so-called “Waggle Dance,” which consists of a series of alternating left-hand and right-hand loops, interspersed by a segment in which the bee waggles her abdomen from side to side. The length of this waggle run increases with the distance flown to reach the food source, and the orientation of the waggle axis relative to gravity specifies the azimuthal direction of the food source, relative to the direction of the sun.
The waggle dance also allows analysis of the bee’s internal representation of space, revealing that she is able to estimate how far she has flown in her search for food. A bee trained to fly around a building or a mountain ridge to reach a food reward signals a direction pointing directly to the food source upon her return, a direction that she has never actually flown. The direction of this novel shortcut is in part based on her experience of the terrain, but the direction and distance to the food can also be calculated using path integration, an internal process by which an animal continuously integrates courses steered and distances travelled along the route into a global vector.
Interestingly, bees flying a circuitous route around an obstacle do not signal the distance of the shortcut, but rather the total distance of the detour. A relevant measurement of distance is important not only for returning to a previously discovered food site but also for communicating the location of the food source to other colony members.
Bees gauge distance flown in terms of the extent to which the image of the environment moves in the eye. In other words, the optic flow experienced by the eye, or the speed of motion of the image of the environment, is integrated over time to obtain a distance measurement. The nature of this visual odometer was unraveled by training bees to fly to a feeder placed inside a short, narrow tunnel. When bees returned to the hive from the tunnel, they indicated a highly exaggerated distance to the feeder (~200•m) despite the fact that they had only flown 6•m. This is because the total amount of image motion depends upon the distances to the various objects that are passed; the closer the objects, the larger the image motion perceived by the eye.
For many years, controversy ensued on whether this dance is really abstract or just a form of gaining the attention of other foragers and directly communicating only the smell of the flower source.
However, through a series of ingenious experiments, the dance mystery is solved. Bees were recruited by scouts to a non-scented food source, then captured leaving the hive, marked with sonar radar, and released several hundred meters from the hive. All the bees flew the exact distance and direction in which they were mobilized. Not finding the food source, they hovered around for several minutes before making the decision to return. They flew back, without finding their hive. How they homed in is the subject of the navigational abilities of bees.
