Plants use sand armour to break teeth of attacking caterpillars

Some plants are coated in sand, and it seems the sand grains act like medieval armour that protects these “psammophorous” plants from munching caterpillars

Some plants may use an odd, yet simple defensive tactic against insect herbivores: sand. New research suggests that some plants use sand grains as an unappetizing and abrasive armour.

Psammophorous (“sand-carrying”) plants have sticky surfaces to which sand adheres. The coating was thought to somehow protect the plants against herbivorous insects, but this was only formally tested in 2016. Eric LoPresti of the University of California, Davis and his colleagues confirmed that plants with a coating of sand are eaten less (Ecology, doi.org/chmj).

However, they also found that the sand does not work by camouflaging the plant. They have now examined what the sand does to herbivores.

The researchers raised caterpillars on beach plants called sand verbenas (Abronia latifolia), which were either sand-covered or “clean”. The caterpillars were either white-lined sphinxes , which take big