A second issue: the animal has the annoying habit of feeding on ripe fruits. Wilting is not caused by the insect itself (feeding usually occurs after another factor has damaged them), but it seems particularly interested in very ripe grapes,  aggregating on them at the end of the season. Because it is difficult to extract the ladybirds during the manufacturing process, they are found inside the wines, whose taste is then affected. Given the craze to create vineyards in Belgium, that is something which could give our (future) viticulturists, a hard time, as it has for their French colleagues.

Finally, a third problem: when Autumn arrives, Harmonia axyridis shows an aggregating behaviour to protect itself from the fall in temperatures. Natural shelters not appearing to be suitable sites for their gathering, they thus settle within building interiors, mostly located in the countryside, and more especially in proximity to the wooded areas it has frequented during ummer. To seal crevices would be useless: it is able to slip into small cracks within frames or walls. In their dozens or hundreds (even aggregations of thousands of individuals have already been observed!), the multicoloured Asian ladybirds then tranquilly overwinter in the folds of curtains or behind walls, their metabolism slowing down throughout the rough season.

If the Winter company of some of these insects may be pleasant, it fails to be when hundreds of animals invade the living or sleeping spaces, staining the supports where they are gathered with an obnoxious yellow liquid when they are disturbed. The substances it contains can sometimes induce allergic reactions: asthma, rhinitis, conjunctivitis, etc. The presence of allergens in the hemolymph has been demonstrated. Quite recent American studies have showed cross sensitivity allergies between the multicoloured Asian ladybird and cockroaches.

Trapping techniques

For all these reasons, their populations have to be controlled, but we should have no illusions: their presence has become inevitable and it is now probably impossible to completely eliminate this invasive species. At the Functional and Evolutionary Entomology of Gembloux Agro-Bio Tech (University of Liege), researchers have been working for a long time on this subject in order to improve the understanding of Harmonia axyridis behaviours. One of their main objectives consists in developing trapping techniques that respect both the ecosystems frequented by animals (other insect species, and in particular other ladybird species, cannot possibly be threatened,) and user safety. An important step has just been taken by thework of Delphine Durieux, a researcher at Professor Eric Haubruge’s Entomology Department, carried out jointly with the Analysis, Quality and Risk Unit (Laboratory of Analytical Chemistry). This research has been devoted to the roles of hydrocarbon chains in the formation of ladybird aggregation in houses. ‘We know, through other research work, that, in Autumn, Harmonia axyridis is attracted by prominent elements in the landscape, standing out clearly on the horizon: mountains, hills, imposing buildings, isolated houses, etc.’ explains the young researcher. ‘We still have to discover what happens after the migratory flight toward buildings: how and why do multicoloured Asian ladybirds form these aggregations? How is the cohesion of their gathering ensured throughout the bad season?’