Harlequins eat native insects in the wild

Published: 23 June 2014 at 16:36

Anglia Ruskin scientists test DNA in gut to discover diet of invasive ladybird species

A new study has used DNA analysis to show that harlequin ladybirds, one of the world’s fastest-spreading invasive insects, are preying on native ladybird species and hoverflies across Europe.

The harlequin ladybird, originally from East Asia and first spotted in the UK in 2004, is larger and more voracious than native British ladybirds.

It is now the second most commonly found ladybird in the UK and the new study, led by Dr Peter Brown and Dr Alison Thomas of Anglia Ruskin University, is the first to use molecular tools to test for the DNA of several native insect species in the guts of harlequins in the wild across Europe.

Although mainly an aphid predator, the harlequin ladybird (Harmonia axyridis) is thought to be responsible for the decline of some native ladybird species, through competition and direct predation. 

This study used molecular techniques (the Polymerase Chain Reaction) to probe for the presence of the DNA of various insects (hoverfly, lacewing and other types of ladybirds) in the guts of harlequin ladybird larvae.  In total, 177 larvae were collected from the wild in England, France, Germany, Slovakia and the Czech Republic, and then tested.

Three of the four target prey species were detected in the guts of harlequins at the following rates: 10-spot ladybird (Adalia decempunctata) 9.6%, 2-spot ladybird (Adalia bipunctata) 2.8% and marmalade hoverfly (Episyrphus balteatus) 2.8%.  The only insect tested for and not detected was the green lacewing (Chrysoperla carnea).  

Dr Brown, Senior Lecturer in Zoology at Anglia Ruskin, said:

“This study shows that harlequin ladybirds in the wild commonly prey on a number of insects, other than just aphids.  The results offer further evidence that the harlequin is a generalist predator which is having a damaging effect on native species across Europe.
“Ladybirds and other aphid-feeding insects are a very important part of ecosystems, acting as natural pest controllers.  There are 47 ladybird species in the UK and it is vital that this diversity is maintained.”

Dr Brown and Dr Thomas from Anglia Ruskin University led the study, in collaboration with the University of Cambridge and Ghent University.  The paper “Intraguild predation by Harmonia axyridis (Coleoptera: Coccinellidae) on native insects in Europe: molecular detection from field samples” is published in the latest edition of Entomological Science.