The Flight Guidance Mechanisms of Honey Bee Swarms : 7 HOW DOES A SWARM FIND ITS WAY TO ITS NEW NEST SITE?
The Flight Guidance Mechanisms of Honey Bee Swarms
Tom Seeley and Ann Chilcott
observes a swarm of bees launch into flight and move off to its new home is presented with a mind-boggling puzzle: how does this school bus-sized cloud of some 10,000 insects manage to fly straight to its new dwelling place? Its flight path may extend for several miles and traverse fields and forests, hilltops and valleys, and even swamps and lakes. What is most amazing is the precision of the flight guidance, for the swarm is able to steer itself to one special point in the landscape, eg, a specific knothole in one particular tree in a certain corner of a forest. And as the swarm closes in on its destination, it gradually reduces its flight speed so that it stops precisely at the ‘front door’ of its new home.
A
The mystery of how the thousands of bees in a swarm accomplish this magnificent feat of precisely oriented group flight has been carefully probed in recent years using sophisticated radar tracking, video recording, and image processing
April 2015 Vol 97 No 4 nyone who
technologies. In this article, we will review the main findings of these investigations.
Defining the Problem
Firstly, let’s define the problem a bit more precisely. Several studies (Seeley, et al, 1979, Seeley and Buhrman, 1999) have revealed that only 3–4% of the bees in a swarm have visited the new home site in advance of the swarm’s move to it. This small minority of well-informed bees consists of all the scout bees that visited the chosen site during the swarm’s process of choosing its dwelling place (reviewed by Visscher, 2007, Seeley, 2010). Therefore, when a swarm flies to its new home, it relies on a relatively small number of informed individuals – some 300 to 400 in an average-size swarm of 10,000 bees – which must lead all the rest to their destination. How does this system of leaders and followers work?
Nasonov Pheromone?
One possibility is that the leaders provide flight guidance by means of the attraction pheromones produced in the
www.bee-craft.com
Nasonov gland that is part of the scent organ at the tip of a worker bee’s abdomen (Figure 1). The leaders might discharge these pheromones along the front of the swarm cloud to attract, and thereby guide, the other bees to move in this direction.
This hypothesis was tested in a study (Beekman, et al, 2006) with three swarms – each consisting of a queen and 4000 workers – in which every worker bee had her scent organ sealed shut with paint. Each swarm was tested for its ability to perform a well-oriented, full- speed flight to a bait hive in the centre of an open field. As a control, three other
swarms of the same size were prepared in which every worker bee had a dot of paint applied to her abdomen but without sealing off her scent organ. Their flight abilities were likewise tested. Both treatment and control swarms flew directly and quickly to the bait hive, but the treatment swarms took much longer than the control swarms (20 minutes versus 9 minutes, on average) to move into the hive once they reached its location.
This experiment showed that the leaders in a swarm do not provide flight guidance using the Nasonov gland pheromones, but that they do
Figure 1. Sections through the abdomen of a worker bee showing (left) her scent organ closed in the rest position and (right) the scent organ exposed by raising the abdomen and tipping the last abdominal segment downward
Illustrations by Tom Seeley
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48
