Phaedon cochleariae

Phaedon cochleariae
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Coleoptera
Family:	Chrysomelidae
Genus:	Phaedon
Species:	P. cochleariae
Binomial name
Phaedon cochleariae (Fabricius, 1792)

Phaedon cochleariae (commonly called mustard beetle or watercress beetle) is a non-social, holometabolous^[1] species of leaf beetle native to Europe.^{[2][page needed]}

They experience distinct personalities that are influenced by population density, sex, inbreeding, and diet. This is exhibited by varying levels of aggression and sexual activity. As non-social creatures, P. cochleariae thrive in lower population densities, where they benefit from reduced competition and abundant resources which improve their individual fitness. They are at a potential risk of extinction because of high levels of inbreeding depression in the wild.

The mustard leaf beetle is a common pest of horseradish and cabbage plants.^[3] Their diet of external leaves makes them overtly visible to predators. Due to their high visibility, they have evolved to secrete defensive and volatile substances, called irdoids, to deter predators. These secretions also contain antimicrobial and antifungal properties.