SEPTEMBER
2005

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

09-08-05

Stinging Insects Are Fear Mongers

Almost everyone has a healthy respect for insects that can sting. And for good reason! Most of us have at one time or another been the victim of a stinging insect. For the most part, being on the receiving end of a bee sting is not a pleasant experience.

In fact, a song from "The Sound of Music" puts it this way: "When the dog bites, when the bee stings, when I'm feeling sad, I simply remember my favorite things, and then I don't feel so bad." Indeed, bee stings are painful enough that most of us try not to repeat the experience.

So which insects sting? Stinging insects are all members of the order Hymenoptera, which includes bees, wasps and ants. How stinging became a way of life for most Hymenoptera is not known. We do know, however, that stingers of insects are modifications of structures used to deposit eggs. Therefore, only female insects can sting.

Most likely it was a sawfly, an insect that in spite of its name is classified with the bees, ants and wasps that used an ovipositor for something other than just depositing an egg. The sawfly uses the ovipositor to cut into the bark of a tree to deposit an egg, hence the reason for the name of this insect.

Many solitary wasps -- those that do not live in colonies -- use a stinger to inject poison into an insect that will become food for their offspring. The poison injected does not kill the host insect, it just paralyzes it.

In this case, the poison keeps the host alive while the immature parasitic wasps feed as they grow. Ultimately, the host is killed. Such wasps are considered beneficial when their host is a pest insect. Wasps that sting their prey seldom sting in defense of themselves or their nest. But if they happen to sting, the result is not considered to be very painful to a human.

That is not the case, however, with the social insects that sting. Such social bees, ants and wasps sting only to defend themselves and their nests. Therefore, the more pain the insect inflicts on the offending animal the better. Of course, that is from the insect's point of view. And the potential pain is the reason that animals try to avoid encounters of the stinging kind.

From the perspective of stinging insects, the threat of a sting also provides protection. Consequently, the development of identifiable colors and sound advertise the presence of an insect capable of delivering a painful attack. Thus, animals that have experienced a sting avoid insects that look and sound as if they might be able to sting.

The chemicals that stinging insects inject into a target are not exactly the same for each species of insect. In honey bees, a chemical called melittin is responsible for the pain. It works by stimulating the nerve endings of pain receptors. To make things worse, the honey bee venom also contains phospholipase and hyaluronidase, which help the melittin reach more cells. When that happens, the animal body responds by releasing histamines that result in itching, swelling and redness. As if this isn't bad enough, the honey bee poison also includes a bit of dopamine and norepinephrine. These chemicals are neurotransmitters that function to create fear and excitement in the affected animal. Once we receive a sting, we never forget it!

Another aspect of stinging of Hymenoptera is that most of these insects can sting more that once. However, the honey bee can only deliver one sting. That is because the honey bee stinger is barbed much like a fish hook. The stinger, therefore, stays embedded in the target animal. This process is very bad for the bee. Her stinger and the associated poison sac and muscles are pulled from her body when she leaves. She dies. But the stinging apparatus continues to pump poison into the target.

It makes sense to remove a honey bee stinger as quickly as possible when stung. The stinging apparatus will pump poison for 30 seconds to a minute. So removing the stinger will reduce the dosage of poison received. Regardless, we will have a sore spot and a memory of the incident. As for the bee, she has given her life for the good of the colony. That is called the ultimate act of altruism. Humans are the only other animal that practices such a thing. We call it the military in wartime.

 

Writer: Tom Turpin
Editor: Olivia Maddox