The leaf beetles are plant-eating insects that form the family Chrysomelidae. There are about known 37,000 species in this family although entomologists believe there are still another 13,000 waiting to be discovered.

About 60 species have been recorded in the Maltese islands so far. One of the local species, Chrysolina bankii, does not seem to have an English or Maltese common name. It is not common and can be recognised by its hemispherical shape, metallic green wings and body and its dark orange legs and antennae.

Both adult and larva of leaf beetles feed on plants. Often a species feeds on just one or on a small number of plant species.

Some leaf beetles have become agricultural pests while others are used to control weeds.

Probably the best known leaf beetle is the Colorado potato beetle, which originated in America where it became a pest of potato plants in the 1840s. It appeared in Belgium soon after World War I and from there it spread to other parts of Europe wreaking havoc wherever it landed.

Some leaf beetles have become agricultural pests

Luckily, it never reached the Maltese islands and in 2008 the EU issued a directive in which Malta and some other countries were declared protected zones. This led to special measures such as plant quarantine to keep the Colorado potato beetle away from the islands.

Plants are not passive victims of herbivores. They are constantly evolving and adapting themselves to reduce the impact of herbivores and improve their survival and reproduction.

Many plants produce chemicals that repel herbivores or are toxic to them. Some plants grow in inaccessible areas such as on cliff faces while others have spines and thorns to deter larger herbivores.

Others divert herbivores to eat non-essential parts while some species encourage the presence of the natural enemies of herbivores such as insect-eating birds.

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