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INSECT BEHAVIOR

 STAGMOMANTIS LIMBATA, the Bordered or Arizona MantisNearly a century ago, in his own backyard, the famous French naturalist J. Henri Fabre  witnessed a little drama in which the participants were a wasp, a bee, and a mantis (a mantis is pictured at the right). But, before we relate his story, we need to know a little about the story's stars.

In any garden not doused with insecticides, in the summer we can spot wasps methodically buzzing from leaf to leaf, searching for something beneath leaf tips. As explained on our Wasp Page, these wasps are looking for spiders or insects, depending on which species of wasp they are. When the wasps capture their prey they sting it in a certain way so that the prey's nervous system is destroyed. The unfortunate creature henceforth remains alive, but is paralyzed for the rest of its life.

Paper nest of waspOnce the prey is immobilized, the wasp carries it to the wasp's nest, which is perhaps a small comb made of paper and placed beneath a house's eave, such as the one shown at the right from an outbuilding where I live, or maybe it's a structure made of mud, or a tunnel dug in the soil. Each wasp species builds a distinctive nest. Inside a cell in its nest (each of those hexagonal-shaped cavities in the comb at the right is a cell), the wasp places its paralyzed prey next to an already-laid wasp egg, then seals the cell. Eventually when the wasp's egg hatches the worm-like larva will find its meal waiting for it, for it will eat the still living but paralyzed spider or insect. The wasp paralyzes its prey instead of kills it because dead prey would decay before the wasp's egg hatches.

This scenario is not extraordinary or even uncommon. It happens around us all the time, even in our own backyards. In North America species of mud-dauber wasps provision their nests with spiders. Vespid Wasps such as hornets and paper wasps (paper wasps made the nest in the picture) typically seal caterpillars next to their eggs. So, now we're ready to consider what Fabre saw.

Fabre studied members of the sphecid wasp family, who prey on honeybees. In North America we have many kinds of sphecid wasp, such as sand-loving wasps who provision their nests with grasshoppers or crickets, and aphid wasps, which prey on hoppers of the Homoptera order. Well, Fabre found that if the sphecid wasp he was watching caught a honeybee swollen with flower nectar, the wasp never failed to squeeze the bee in a certain way to cause the bee to disgorge its syrup, and then the wasp would lick the bee's tongue dry before sealing it into its nest.

One day as Fabre watched a sphecid wasp licking the nectar from a captured honeybee's tongue the wasp itself suddenly fell victim to an even larger and more aggressive insect predator, a true Tyrannosaurus rex of the insect world, the Praying Mantis, Mantis religiosa, like the one pictured at the top of this page. Fabre's mantis ensnared the wasp in its saw-like front legs and immediately set about munching the wasp's belly.

Here is what even the seasoned naturalist Fabre referred to as "an awful detail": As the mantis devoured the wasp rear-end first, the wasp's front part never ceased licking the honey bee's tongue...

What does it all mean?

There's a singular beauty in Fabre's story. Before the beauty becomes apparent, however, it's absolutely required that we abandon our human perspective. It is at this point that we must begin "bending our minds" away from human emotionalism, so that we can consider the insects' inherited instinctual drives in a detached, analytical manner.

Nowadays many people, including no-nonsense biologists, are beginning to admit that higher animals such as chimpanzees, porpoises, and even dogs and cats have degrees of insight, and maybe even emotions, though of profoundly different nature than what we humans experience. However, no genuine scientist has made the case for any insect ever displaying emotions or insight. The point Fabre wished to make with his story was that insects do not think; insects behave strictly according to instinct.

It's quite as if insects were little machines with computers instead of brains. The insect experiences a stimulus, such as noticing that a bee's crop is filled with nectar, and its automatic response is to squeeze the bee in a certain way and lick the bee's tongue. This response is as automatic as the process of hitting the Ctrl-Alt-Delete keys on your keyboard, which causes your computer to hot boot (and you lose all the info in your RAM, so don't do it right now!). Nature programmed Fabre's wasp to lick the bee's tongue because mother wasps need the honey's energy for themselves. There's nothing personal, nothing evil, nothing sneaky about the behavior. It's all programmed right there in the wasp's genetic code.

To further make his point, Fabre describes another of his classic experiments. One wasp species always drags its demobilized victims to the nest by tugging on the prey's antennae. When Fabre snipped off the preys' antennae, the wasp couldn't figure out to grab another part of the prey's body -- a mouthpart or front leg, for instance. The wasp was programmed to pull its paralyzed prey by the antennae, and it simply didn't have the intelligence to do anything other than what its instinct told it to do.

Recent studies have brought to light some information that at first glance seems to contradict this "little computer" view of bugs.  For instance, very sensitive microphones were attached to twigs on which several of a certain kind of insect called treehoppers were sitting, apparently placidly sucking juice from the stem. The microphones revealed that when young treehoppers were threatened they made a special sound that brought their mother treehopper running to protect them.

Is this purely "programmed behavior"?

Maybe it is. Or maybe there's a glimmer of something there that goes a tiny bit beyond simple machinelike "stimulus and response" ... The next generation of entomologists -- of "insect scientists" -- have some very interesting questions to answer!

You may be interested in reviewing books covering insect behavior, available at Amazon.com in both the USA and the UK, by clicking here..