Role of long-chain hydrocarbons in the aggregation behaviour of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae)

Abstract

a b s t r a c tThe multicoloured Asian ladybirds, Harmonia axyridis (Pallas), form large aggregations inside dwellings to survive cold winters, causing annoyance to householders due to their abundance, allergenic properties and problems consequent on reflex bleeding. Flight to overwintering sites and macrosite choice of this species is well documented. H. axyridis shows a hypsotactic behaviour and a clear preference for contrasting visual elements. However, how the microsite is selected remains undocumented, although a better understanding of the factors implicated could lead to the development of new control methods for this pest.In this work, we hypothesised that non-volatile compounds are involved in the microsite choice and aggregation of this beetle. Long chain hydrocarbons were identified at aggregation sites, comprising saturated and unsaturated homologues. An aggregation bioassay was then conducted on overwintering individuals, highlighting the retention capacity of the identified compounds on the tested ladybirds. Additional investigations showed that H. axyridis males and females, originating from overwintering sites, deposit a similar blend of molecules while walking. A Y-shaped tube assay revealed that this blend is used by male and female congeners as cue allowing individuals to orientate towards the treated side of the olfactometer. These results suggest the use of two different blends of long chain hydrocarbons by H. axyridis during its aggregative period, the first one to lead conspecifics towards aggregation sites (microsites) and the second to ensure the cohesion of the aggregation. These findings support the potential use of these blends, in association with volatiles, in the design of traps in order to control infestations of this species in dwellings.

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

“…Overwintering individuals are also more likely to follow this chemical mark than individuals collected in spring or summer. The overwintering surface is also chemically marked with a similar chemical blend, comprising the same molecules but in different ratios (Durieux et al, 2012). This suggests there are two different blends of long-chain hydrocarbons, the first leading conspecifics toward aggregation sites and the second ensuring the cohesion of the aggregate.…”

“…During aggregation, adult H. axyridis show mutual interactions, and should therefore be considered as social aggregators. In addition to the physical contacts between congeners (Durieux et al, 2014a), laboratory assays have shown that chemical markings are involved in this aggregation behavior (Durieux et al, 2012). Non-volatile long-chain hydrocarbons are passively deposited by walking males and females on the surfaces surrounding the aggregation site (Kosaki and Yamaoka, 1996;Durieux et al, 2012).…”

“…In addition to the physical contacts between congeners (Durieux et al, 2014a), laboratory assays have shown that chemical markings are involved in this aggregation behavior (Durieux et al, 2012). Non-volatile long-chain hydrocarbons are passively deposited by walking males and females on the surfaces surrounding the aggregation site (Kosaki and Yamaoka, 1996;Durieux et al, 2012). The chemical composition of the marking varies with the season, being richer in unsaturated hydrocarbons in winter than in summer (Durieux et al, 2013).…”

The harlequin ladybird, Harmonia axyridis: global perspectives on invasion history and ecology

“…The relative attractiveness of different 411 surface colours has been studied; white is the most attractive colour followed by yellow and black 412 then green then red and finally natural wood (Wang et al 2011). Volatile aggregation pheromones 413 are not involved in this orientation (Nalepa et al 2000) but it is apparent that contact 414 chemoreception is important in the establishment of large aggregations (Durieux et al 2012). 415…”

Mating Status Influences Cold Tolerance and Subsequent Reproduction in the Invasive Ladybird Harmonia axyridis

“…It is considered to be bivoltine but up to five generations per year have been observed (Bazzocchi et al, 2004;Nedved and Honek, 2012). In winter months, the species aggregates in concealed and sheltered locations that provide a protective microclimate (Berkvens et al, 2010;Wang et al, 2011;Durieux et al, 2012;Raak-van den Berg et al, 2012). It might be advantageous for a female to be fertilized before leaving these overwintering aggregation sites, as this would allow females to found populations even without males .…”