Submitted to: Bulletin of Insectology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2009
Publication Date: 5/8/2010
Citation: Riddick, E.W. 2010. Ectoparasitic mite and fungus on an invasive lady beetle: parasite coexistence and influence on host survival. Bulletin of Insectology. 63 (1):13-20, 2010.
Interpretive Summary: The multicolored Asian lady beetle Harmonia axyridis has received much attention in recent years for its usefulness as a natural enemy of soft-bodied insects (such as aphids) in various crops during the spring and summer. Unfortunately, it is also known for its annoying behavior of invading houses during the fall and winter seasons. A parasitic mite and a parasitic fungus were found infecting this lady beetle. The infection slightly reduced the winter survival of the lady beetle. This is the first report of a parasitic mite attacking this lady beetle under natural conditions. The two parasites may affect commercial shipment and storage of this lady beetle for biological control of pests.
Technical Abstract: Harmonia axyridis is an invasive generalist predator originating in Asia, but now distributed in North and South America, Europe and southern Africa. The naturally occurring enemies (parasites, pathogens, parasitoids) that attack H. axyridis are not well-known. A parasitic mite, Coccipolipus hippodamiae, and parasitic fungus, Hesperomyces virescens, were discovered on H. axyridis adults in winter aggregations. The mite attached to the underside of the elytra of male and females. The fungus was on the outer surface of the elytra and abdomen of males or elytra of females. This discovery provided an opportunity to test these hypotheses: (1) presence of mite does not affect the prevalence or intensity of fungus when both coexist on the same host and (2) parasitism has no influence on host survival during the winter season. The mite had no effect on the prevalence of the fungus. When the mite was present on a shared host, intensity of the fungus was lesser on the elytra of males and females but greater on the abdomen of males. Parasitism had a slight effect on the survival of cold-stressed and food-deprived male beetles. This study contributes to our knowledge of the interactions between parasitic mites and fungi and their coccinellid hosts. The flexibility of the fungus to develop on dorsal and ventral host body surfaces may provide opportunities for coexistence of the mite on shared hosts. Further research is necessary to determine the influence of these parasites on the population dynamics of H. axyridis.