Comparison of the Sex Pheromone Composition of Harmonia axyridis Originating from Native and Invaded Areas

The multicolored Asian lady beetle, Harmonia axyridis (Coleoptera: Coccinellidae),
originates from South-East Asia and is now considered as an invasive species at a worldwide
scale, with populations encountered in North and South America, Africa, and Europe. Several
previous studies suggested that invasive populations display di erent behavioral and physiological
traits, leading to a better fitness than native individuals. H. axyridis sex pheromone was identified
recently, but only from individuals established in Europe. In this study, we compare the composition
of the female sex pheromone of H. axyridis from two populations: (i) an invasive population in North
America, and (ii) a native population in South-East China. We found the females originating from
both populations to release in similar proportions the same five pheromonal compounds, namely
-caryophyllene, -elemene, methyl-eugenol, -humulene, and -bulnesene. However, females
from the North American strain release all five compounds in larger amount than the Chinese ones.
Whether invasive individuals were selected during the process of invasion through their capacity to
better call and find sexual partners remains to be confirmed.