permaculture

["Lawrence F. London, Jr." <lfl@intrex.net>]

<http://news.bbc.co.uk/2/hi/science/nature/4460030.stm>


BBC listens in to insect chatter
        
The alcon blue lives on boggy heathland

Enlarge Image
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

Enlarge Image
"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."