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THE passion fruit vine produces “gas bombs” in its leaves that release deadly
cyanide when eaten. This keeps most creatures at bay, but Helene Engler of the
University of Texas at Austin and her colleagues have now found that the larvae
of the South American butterfly Heliconius sara can outwit the
plant’s defences. Far from being poisoned, the caterpillars use cyanogen, the
cyanide precursor found in the vine’s leaves, as a source of nitrogen
(Nature, vol 406, p 144). “This is the first example of an insect capable of
cyanogen metabolism while avoiding the internal release of toxic cyanide,”…