Aggregation behavior of Harmonia axyridis under non‐wintering conditions

Abstract

The invasive multicolored Asian ladybeetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), aggregates inside dwellings during winter to avoid cold weather. This adaptive behavior disturbs homeowners, because of the large numbers of individuals that aggregate, which induces allergic reactions. The migratory flight patterns of this species have been well documented, with individuals preferentially moving toward prominent and high color contrast elements. However, the factors involved in the selection of aggregation sites by this species have yet to be elucidated. Here, we evaluated the influence of (i) the density of individuals and (ii) the type of available shelters on decisions by H. axyridis to settle and aggregate under shelters. A dual choice bioassay conducted in the laboratory demonstrated the presence of mutual attraction to conspecifics. We also found that individuals preferentially settled under red covered shelters compared to transparent shelters, and that the type of shelter outweighed the effect of social interactions among conspecifics. Moreover, this experiment was performed under non-wintering conditions, providing the first evidence that aggregative behavior in this species can also occur under those specific conditions.

Behavioral and Immunological Features Promoting the Invasive Performance of the Harlequin Ladybird Harmonia axyridis

“…Many insect species show aggregation behavior, which has a range of benefits including enhanced defense, better access to mates, food location and utilization, prevention of desiccation, and regulation of internal temperature. Many beetle species aggregate, and this behavior can be observed at any time of year in H. axyridis (Durieux et al, 2015). This behavior can be a nuisance to humans, e.g., in vineyards, adult H. axyridis aggregate on ripe grape clusters.…”

Molecular Cloning and Induced Expression of Six Small Heat Shock Proteins Mediating Cold-Hardiness in Harmonia axyridis (Coleoptera: Coccinellidae)

“…In the north of China, H. axyridis melanic and non-melanic types vary seasonally: in the summer adults are mainly black and the number of yellow type adults significantly increases in the autumn (Wang et al, 2009 ); in winter, the proportion of yellow type H. axyridis was significantly higher than that of black adults. To survive through the cold winter, H. axyridis individuals move to concealed and sheltered locations where they aggregate, creating a protective microclimate in which insects experience less extreme temperatures than in the surrounding areas (Berkvens et al, 2010 ; Durieux et al, 2015 ). In Northeast China, adults aggregate in some fixed locations where they overwinter (Wang et al, 2011 ).…”

Symbiont‐mediated chemical defense in the invasive ladybird Harmonia axyridis

“…In conjunction with other traits such as coloration, gregarious behavior, and reflex bleeding that are primarily defensive, MPs have likely been co‐opted as aggregation pheromones (Wheeler & Cardé, ). MPs are also associated with inducing aggregation; for example, A. bipunctata spend more time in the vicinity of an MP source when an extract containing cuticular hydrocarbons from diapausing individuals was present (Durieux et al, ; Susset et al, ). In H. convergens , IBMP has the strongest aggregative effect, whereas beetles aggregate only in specific doses of SBMP, while IPMP is repellent.…”

“…Both non-diapausing and diapausing beetles produced MPs ( Figure 1), indicating that the potential aggregating pheromone of reflex bleeds are also produced under nonwintering conditions (Durieux et al, 2015;Jeanson & Deneubourg, 2009). However, these data also indicate the relative proportion of SBMP, IPMP, and IBMP differed between non-diapause and diapause, such that a change in the relative proportion within the MP cocktail could enable the beetles to use the same set of volatile compounds to display different signals under different conditions (Figure 1b-d).…”