Hi András,

Numerous papers deal with intra-guild predation by Harmonia axyridis, and decline of native species after Ha introduction. Please check, for instance, the papers attached.

Best regards,

Thibaut

Article Predation of native coccinellids by the invasive alien Harmo...

Article Molecular analysis of the gut contents of Harmonia axyridis ...

Conference Paper Harmonia axyridis implicated in native European ladybird declines

Article Decline in native ladybirds in response to the arrival of Ha...

Article Invasive alien predator causes rapid declines of native Euro...

Article Intraguild predation involving Harmonia axyridis: A review o...

Hi András,

Numerous papers deal with intra-guild predation by Harmonia axyridis, and decline of native species after Ha introduction. Please check, for instance, the papers attached.

Best regards,

Thibaut

Article Predation of native coccinellids by the invasive alien Harmo...

Article Molecular analysis of the gut contents of Harmonia axyridis ...

Conference Paper Harmonia axyridis implicated in native European ladybird declines

Article Decline in native ladybirds in response to the arrival of Ha...

Article Invasive alien predator causes rapid declines of native Euro...

Article Intraguild predation involving Harmonia axyridis: A review o...

In Belgium, Adalia bipunctata is clearly threatened since the arrival of Harmonia axyridis. This is a personal observation, also confirmed by this publication.

Article Predation behaviour of Harmonia axyridis on Adalia bipunctata

Hi Thierry,

I confirm your observation. However, I was quite surprised to discover several populations of Adalia bipunctata around Brussels last year (after years of decline and almost total absence). It would be nice to confirm this observation in 2015 (in Brussels and elsewhere). If it is the case, it would be interesting to understand what is going on exactly: perhaps A. bipunctata was able to adapt? I'm sure our Belgian cox friends (for instance Tim Adriaens, Gilles San Martin...) will provide new insights in the near future. 

Best,

Thibaut

Hi,

While working on the Harmonia case in Switzerland, the most impressive fact was the exponential increase of this ladybird part in the ladybird communities. In a couple of years, it became the major ladybird and the population of other ladybird started to decreases.

As for every aphidophagous ladybird population, this one is also really dependent on the availability of prey. We also observed years where sites that previously were highly colonised being coccinellids free because no aphids were present. That might be something to take in account Thibaut about A. bipunctata

Regards

Yes. Harmonia axyridis is a dominant  coccinellid and predator of the larvae of Coccinella septempunctata and Coccinella novemnotata.In the New England region the two species are very scares, specially C. novemnotata!

Dear All,

Many thanks for your suggestions on well known publications. I am interested in data experienced in field studies not in laboratory forced experiments or in studies repeating guesses. In North America from 1885 about 179 adventive coccinellid species have been introduced however, some adventive species become dominant their correct ecological role could not have been proved. See e.g. Harmon et al. (2007): The decline of native coccinellids (Coleoptera: Coccinellidae) in the United States and Canada. J. Insect Conserv. 11: 85-94.

I always prefer to cite publications, but as it is a recent phenomenon and  I spend more than 4 months on the field every year since the invasion started, for once I will speak from personal experience (in France).

H. axyridis looked like a threat during the first years of the invasion (2008-2011 approximately) but since, the populations of native species have not suffered from its presence and it seems we arrived at an equilibrium situation.

At first there were so many H.axyridis (and as they were overwintering in or near houses, they were really conspicuous and annoying) that everyone thought it would be a huge threat for C. 7-punctata, A. bipunctata and some other Adalia species. Indeed larvae of H. axyridis do eat larvae of other species in case they cant find aphids, I saw it on the field sometimes. But nowadays the populations of H. axyridis have decreased a lot in France, at least in the areas I know, and the other native species are still as present as before.

That is why many publications used "early evidence" and such expressions when trying to prove that H. axyridis would cause the extinction of our native species (which particularly touched people, as ladybirds are umbrella species) .

People often like to draw quick pessimistic conclusions about invasive species, particularly when it might affect one of the very rare insect they love, but they forget that it takes several years to really know how the situation will evolve and stabilize. In that case, I can't be sure we have come to this balanced situation yet, but what I'm sure of is that I no longer see thousands of H. axyridis in every corner of the room every autumn, and I still can find as many  Coccinella or Adalia species on the field.

Some of the studies seem to show different trends at least in Britain, so what I observe on the field every year in France might not be true in other European countries. But I would recommend caution and patience when it comes to invasive species and ladybugs ;)