Zigbee

Recently my wife was telling me about a great book by Amulya Malladi titled ‘The sound of language’. I am yet to read it myself, but it is supposedly great reading and about an Afghani lady Raihana in Denmark for whom the Danish language itself sounded like the buzzing of many bees. Gunnar whose wife passed away needs somebody to look after the bees she left behind. Raihana takes up the challenge. But well, this is not a book review, but have any of you wondered how bees communicate?

The domestic honeybee, a colonial insect, lives in a hive that contains a queen, a few male drones, and thousands of worker bees. The survival, success, and future of the colony is dependent upon continuous communication of vital information between every member of the colony. The technique that honey bees use to communicate new-found food sources to other members of the colony is referred to as the ZigBee Principle. Using this silent, but powerful communication system, whereby the bee dances in a zig-zag or waggle pattern, she is able to share information such as the location, distance, and direction of a newly discovered food source to her fellow colony members.

And let me assure you – it is a well thought out and scientific approach where time, distances and direction comes into picture.

Wikipedia explains - A waggle dance consists of one to 100 or more circuits, each of which consists of two phases: the waggle phase and the return phase. To examine how bees communicate using waggle dances, let us follow the behavior of a bee upon her return from a rich, new food source. Excited by her discovery, she scrambles into her hive's entrance and immediately crawls onto one of the vertical combs. Here, amidst a massed throng of her sisters, she performs her dance. This involves running through a small figure-eight pattern: a waggle run (aka waggle phase) followed by a turn to the right to circle back to the starting point (aka return phase), another waggle run, followed by a turn and circle to the left, and so on in a regular alternation between right and left turns after waggle runs. The waggle phase of the dance is the most striking and informative part of the signaling bee's performance.

The direction and duration of waggle runs are closely correlated with the direction and distance of the patch of flowers being advertised by the dancing bee. Flowers located directly in line with the sun are represented by waggle runs in an upward direction on the vertical combs, and any angle to the right or left of the sun is coded by a corresponding angle to the right or left of the upward direction. The distance between hive and recruitment target is encoded in the duration of the waggle runs. The farther the target, the longer the waggle phase, with a rate of increase of about 75 milliseconds per 100 meters.

Amazingly, waggle dancing bees that have been in the hive for an extended time, adjust the angles of their dances to accommodate the changing direction of the sun. Therefore bees that follow the waggle run of the dance are still correctly led to the food source even though its angle relative to the sun has changed.

This is a subject that has intrigued researchers since Aristotle’s days in 330BC. Amongst the most famous recent researchers is German Karl Von Frisch who observed and studied the waggle dance for over a decade and was awarded a Nobel Prize for his discoveries in 1973. Contesting this theory is AM Wenner from University of California who came up with an odor plume theory. It appears that the real answer could lie between the two theories or a combination of both.

The reasons for Wenner’s objections were the following - Bees certainly dance, but there is typically a time lag between performance of the dance and other bees' arrival at the food source. The time lag led scientists to suggest that the bees were actually finding the food on their own, possibly by following a scent or the original bee when it returned to the food source. The controversy was created by von Frisch himself when he said that recruits read the dance and flew directly to the food source.

But now a team at Rothamsted Research, an agricultural research center, has tracked bees by radar as they flew to a food source. The team's results show that bees do read the dance and fly off immediately in the direction indicated. In addition, the bees correct for wind drift by looking at the ground and the angle of the sun and correcting any lateral shift. "The mean error is about 5 to 6 meters." Once the bees get to the end of the flight, they change their flight pattern and start circling, looking for the food they've been instructed to find. That takes time, Riley said, and bees can loop back and forth for up to 20 minutes

To track bees by radar, the researchers first had to create a transponder small and light enough that a bee could carry it. It took approximately two years, Riley said, to come up with a system that worked efficiently and was small enough for the insect to carry. It had to be omni directional, and robust enough to survive being attached to the insect and to stay on during grooming. The final version weighs approximately 10 to 12 milligrams, a fraction of the pollen load bees are accustomed to carrying.

But questions remain, said Seeley. "We don't know yet how a bee standing next to a dancer in the darkness of a beehive is able to get all this information from the dancer," he said. "And we also don't know how it evolved." The work was published May 12 in ‘Nature’.

Wenner does not agree - Wenner, the professor emeritus of biology and natural history at UC Santa Barbara, insisted in a telephone interview Wednesday that every experiment so far had been designed simply to confirm the original von Frisch hypothesis - not really to test it. The new research is more of the same, he said. As for Riley's radar experiment, Wenner insisted that capturing the bees and planting the tiny devices on them would send all the bees flying in panic in whatever direction the returning bee had come from. "Any experienced beekeeper knows that if you put a transponder on a bee, it will cause a 'flight' response, and all the other bees around it will fly in the same direction," he said. "This research has all sorts of problems with it because they're trying to prove something they think is true -- but scientists are suckers for the exotic, and this controversy will go on and on for decades."

Remember the usage - He made a beeline for the girl, bar, buffet, food etc – derived from the straight lines that bees fly to reach an intended food destination. "There is no disagreement among scientists that returning foragers dance in the hive. Everyone also agrees that once a forager locates a good food source, she will be able to fly directly to and from that flower patch. That is, she flies a straight line (a bee-line) to the food patch from the hive using local landmarks and the sun for orientation."

The waggle dance was termed ‘Zigbee’ by marketing whiz kids and is the term used for a new definition of communication for wireless networks, which could become very popular soon. Here are details for the technically oriented reader.

A wireless network used for home, building and industrial control. It conforms to the IEEE 802.15.4 wireless standard for low data rate networks. With a maximum speed of 250 Kbps at 2.4 GHz, ZigBee is slower than Wi-Fi and Bluetooth, but is designed for low power so that batteries can last for months and years. The typical ZigBee transmission range is roughly 50 meters, but that can vary greatly depending on temperature, humidity and air quality. A ZigBee mesh provides multiple pathways from device to device (like the Internet) and eliminates a single point of failure. If nodes go down or are removed, ZigBee devices can "zig" and "zag" through the network to their destination like a bumblebee.

Well I can tell you that this wireless ‘zibee’ is definitely buzzing

Other references
A Telegraph article
Wikipedia – Waggle dance
Zigbee definition Techweb
A complete paper on waggle dance
Watch this you tube video to see a real dance with results explained
NCSU animated tutorial
Indrani’s blog on Honeybees