By Dylan Voeller and James Nieh
1. Africanized honeybee feeding on water
I.††††††††† Principles & concepts introduced in this exercise
††††††††††† A.††††††† What are Africanized honeybees?
††††††††††† B.††††††† What makes them dangerous?
††††††††††† C.††††††† Why are they so aggressive? Predation & evolution.
How did they come to the
Africanized honeybees are of the same species as the more
well known European honeybee but belong to a different race or subspecies, meaning that they have similar characteristics
but come from different geographic regions. The two look nearly identical,
and can only be distinguished from one another by measuring differences
under a microscope and analyzing their DNA. Thus the variation between
these two types of bees can be attributed mostly to differences in behavior
as affected by climate, predator abundance, and resource distribution.† European honeybees, as their name suggests,
evolved in areas of
Figure 2.† Aggression is not just limited to Africanized honeybees! Take a look at this stingless bee attacking an Africanized honeybee.† For more information, please take a look at the exercise on stingless bee aggression.
The constant pressure from a higher concentration of predators in the tropics has also affected the evolution of Africanized honeybees, making them more aggressive since they are constantly having to ward off hungry nest attackers.† Africanized honeybees are very sensitive to alarm pheromone (the odors, smelling a bit like banana, which foragers release from their sting gland and glands located in the head when they are alarmed) and produce much more of it than European honeybees.† Africanized honeybee venom is not more painful or voluminous than temperate honeybee venom, its just that many more bees will sting!† The threshold for stinging response in Africanized honeybees is much lower; only a minor disturbance such as a slight motion, vibration, or odor is needed. A study by Collins (1985) showed Africanized honeybees respond 2.4 times faster to alarm pheromone and about 30 times as fast to a moving target! Once Africanized bees have been stimulated, they are also much more likely to respond in group attacks. During such attacks they will sting anything in sight that is moving and may pursue a source of disturbance for up to a kilometer (Winston 1992).
biology of Africanized bees, including their higher level of aggressiveness,
is thought to play a role in their successful invasion throughout the
III.†††††† Discussion questions & exercises
††††††††††† Run away in a straight line and through trees or foliage if possible (the bees will have a harder time chasing you. Also, cover your eyes/ears/face as much as is practical.
Find shelter that bees cannot get
into (a car or house for example). Stay in the sheltered area even if
a few bees come inside with you; Africanized bees (like European bees)
will die after stinging once, and it is better to deal with a few bees
than a whole swarm.†Do not allow
yourself to become trapped in any area you can't get out of:
people have died as a result of hiding in caves with only a single exit.
Do not jump into water: there is a danger
of drowning as a result of panic, and when you surface for air the bees
can follow and sting you.
Do not jump into water: there is a danger of drowning as a result of panic, and when you surface for air the bees can follow and sting you.
Remove the stings as quickly as possible, because they continue to release venom after you are stung.† Wash areas where you have been stung and apply ice if swollen.† If you have difficulty breathing, are allergic to bee stings, or have been stung more than a few times contact a doctor as soon as possible.
B.†††††††† If you met an Africanized honeybee on a flower far away from its nest, would it be more dangerous than a normal honeybee?
††††††††††† No.† Africanized bees are aggressive only if they are being threatened, or if an intruder comes too close to their nest.
C.†††††††† Aside from humans, what animals are bee predators?
††††††††††† Many types
of animals attack beehives in order to obtain food from the honeycomb,
or to use the bees themselves as food.†
Mammals are the most destructive predators because they exclusively
feed on the honeycomb, usually tearing it apart with their strong limbs
and claws.† Common predators include bears, sloths, badgers, and some birds. Even small predators
such as ants and wasps can be deadly to bees, either because they are
too small to effectively sting, or because they have good armor.
Even small predators such as ants and wasps can be deadly to bees, either because they are too small to effectively sting, or because they have good armor.
D.††††††† Do bees have effective defenses against these predators?
Yes, bees can use threatening behavior (buzzing around an attacker) and ultimately they can sting (releasing painful venom) to ward off or even kill an attacker. Bees are stimulated to attack by vibrations, dark colors, hair, and carbon dioxide. This makes sense because mammals, which are common predators of bees (see above), are hairy, often dark colored, and exhale carbon dioxide.† If you think about this you will realize that bees are drawn towards attacking sensitive areas around the head of a common predator.†
Some websites offering further information on Africanized bees:
Collins, A.M., 1985. Africanized
Crane, E., 1990. Bees and beekeeping:
science, practice, and world resources.
Ratnieks, F., and Visscher, P.K., 1996. Sinaloan beekeepers adapt pollination to Africanized bees.
M.L., 1992. Killer bees: the Africanized
honey bee in the