Eric LoPresti
SOME plants have an odd defensive tactic against insects. It seems they use sand grains as abrasive armour that damages the insects’ teeth.
These “psammophorous” plants have sticky surfaces to which sand adheres. This sand was suspected to be involved in protecting against herbivorous insects, but this was only tested in 2016. Eric LoPresti of the University of California, Davis, showed that plants with sand coats are eaten less. LoPresti and his colleagues have now examined why.
The team raised caterpillars on beach plants called sand verbenas (Abronia latifolia), which were either sand-covered or “clean”. Some caterpillars were white-lined sphinxes, which take big bites of leaves. Others were “leaf-miners” that eat the leaf interior. The team tracked their growth and behaviour.
The leaf miners were equally happy on sandy or clean plants, but more than 80 per cent of white-lined sphinx caterpillars preferred clean foliage. Eating sand hobbled