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Advanced camera and sound techniques are giving scientists remarkable
new insights into insect behaviour.
Caterpillars of large blue butterflies have been shown to communicate
with ants, making noises that fool them into caring for the larvae as if
their own.
And scientists are now looking into the idea that these sounds are
actually overheard by the wasps that seek out such caterpillars to lay
eggs in them.
It is one of many amazing tales to be found in TV's Life in the Undergrowth.
The new BBC natural history series from Sir David Attenborough starts on
Wednesday.
We can get up close and tight, and then you see mind-blowing things
Sir David Attenborough, TV naturalist
See show highlights
It shows invertebrate activity never before caught on television cameras.
"In the past, in order to get close to something, you had to pour light
on it; so much so you were at risk of frying the thing - and you
certainly inhibited natural behaviour," Sir David said.
"We've now got such sensitive electronic cameras that we don't need that
amount of light, and we've also got tiny, tiny lenses; so we can get up
close and tight, and then you see mind-blowing things."
Seek and destroy
The alcon blue butterfly (Maculinea alcon) of central Europe has long
been recognised as a great con artist.
Its caterpillar emits sounds and a chemical signal which essentially
"instructs" worker ants to pick it up and carry it back to their nest,
where it is fed, cleaned and cared for as if it were one of the queen
ant's own brood.
The TV series shines a light on the glories of the undergrowth
In pictures
The caterpillar can live for up to two years inside the nest before
pupating into a chrysalis, from which a new butterfly emerges.
It has an enemy, however: a parasitic wasp (Ichneumon eumerus). Unlike
the ants, the wasp seems to know an impostor is present and, in what
appears like a kamikaze manoeuvre, will enter the nest to find the
caterpillar.
Jeremy Thomas, from the Centre for Ecology and Hydrology (CEH) in
Dorset, UK, has been studying large blue butterflies for over 30 years
and recently discovered how this wasp avoids death by releasing a
chemical signal, or pheromone, of its own.
[The ants] go to the microphones and tap them with their antennae
Dr Jeremy Thomas, Centre for Ecology and Hydrology
This not only repels the ants but causes them to attack one another. In
the midst of this confusion the wasp seeks out the caterpillar and
injects an egg deep inside its body.
When the wasp leaves the nest everything returns to normal and the
caterpillar is once again fed and cleaned by the ants. But, when it
turns into a chrysalis, it is eaten from the inside by the injected wasp
grub - and it is the wasp that emerges to fly from the nest, not another
alcon blue butterfly.
The right tune
Photographing all of this for TV is a first; but the great breakthrough
for the scientists has been in getting clear recordings of the noises
made by the blue caterpillars.
What is more, the CEH team has been able to show just what a direct
effect these sounds have on the ants.
"We can get clean sounds and, using miniature equipment, we can get the
caterpillars and ants behaving much more naturally than in the past," Dr
Thomas told the BBC News website.
The wasp is exceedingly rare and finding a grub is essential
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"Also, we can now play the sounds back to the ants, and that shows the
sounds of the caterpillar match the ant it lives with much more closely
than anyone thought previously.
"The ants react to the sounds in a positive way. They go to the
microphones and tap them with their antennae."
But what of the wasp? The emerging hypothesis is that it hears these
sounds, too. And although the ants may be fooled into thinking the
caterpillar is one of their own, the wasp is not.
"The chemical signal used by the butterfly is so like the ants' own
chemicals that it fools them deep down in the nest. These are not
volatile chemicals either - they're ones you have to touch. So, we
reason the wasp doesn't 'sniff' out the caterpillar," Dr Thomas explained.
"The sounds on the other hand are designed to travel over distances, and
we suspect that's what the wasp is using."
[permaculture] BBC NEWS | Science/Nature | BBC listens in to insect chatter,
Lawrence F. London, Jr., 11/23/2005