Beetles discharging boiling hot chemicals, moths that spiders find hard to swallow, and ' Spanish fly ' flavoured frogs' legs. are examples described by Professor Thomas Eis ner, Cornell University. New York. to illustrate the importance of chemical relationships in the natural world.
He tells GEOFF WATTS how a chemical can become both a repellant and attractant - the yin-yang of ' chemical ecology '.
Producer MICHAEL BRIGHT