''Listronotus elongatus'' is a

weevil Weevils are beetles belonging to the Taxonomic rank, superfamily Curculionoidea, known for their elongated snouts. They are usually small, less than in length, and Herbivore, herbivorous. Approximately 97,000 species of weevils are known. They b ...

native to South America, of the genus of underwater weevils '' Listronotus''. It lays eggs on and eats the invasive floating pennywort (''

Hydrocotyle ranunculoides ''Hydrocotyle ranunculoides'', known commonly as floating pennywort, or floating marshpennywort, is an aquatic plant in the family Apiaceae. It is native to North and South America. Origin and invasiveness Water pennywort is an aquatic plant, ...

''). The

larvae A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

also eat into the stems, reducing the pennywort's ability to grow. Despite not being native to Britain, it has been introduced into waterways in Britain for

biocontrol Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also invo ...

of the floating pennywort, following extensive research to establish that the weevil is not a threat in itself.

References

Curculionidae Beetles described in 1939 {{Curculionidae-stub