Abstract
The harlequin ladybird Harmonia axyridis (Coleoptera: Coccinellidae) has rapidly spread in several continents over the past 30 years and is considered an invasive alien species. The success of H. axyridis as an invader is often attributed to weak control by natural enemies. In this paper, we provide an overview of current knowledge on predators and parasitoids of H. axyridis. The common feature of predators and parasitoids is that they directly kill exploited organisms. Currently available data show that H. axyridis, displaying a variety of chemical, mechanical, and microbiological anti-predator defenses, is usually avoided by predators. However, some birds and invertebrates can eat this ladybird without harmful consequences. The primary defenses of H. axyridis against parasitoids include immune response and physiological and nutritional unsuitability for parasitoid development. These defenses are probably relatively efficient against most ladybird parasitoids, but not against flies of the genus Phalacrotophora. The latter are idiobiont parasitoids and hence can evade the host’s immune response. Indeed, rates of parasitism of H. axyridis by Phalacrotophora in the Palaearctic region (both in the native range in Asia and in Europe) are relatively high. While strong evidence for enemy release on the invasive populations of H. axyridis is lacking, several cases of parasitoid acquisition have been recorded in Europe, North America, and South America. We conclude that enemy release cannot be excluded as a possible mechanism contributing to the spread and increase of H. axyridis in the early stages of invasion, but adaptation of parasitoids may lead to novel associations which might offset previous effects of enemy release. However, further work is required to elucidate the population-level effects of such interactions.
Highlights
The harlequin ladybird Harmonia axyridis (Pallas) is a species of Asiatic origin that became invasive in the late 1980s in North America and subsequently in other continents
This review focuses on predators and parasitoids of H. axyridis
Harmonia axyridis is a host of D. coccinellae (Fig. 3), with reports both within its native range and in all invaded continents (Table 2), but parasitism and emergence rates are usually low in comparison with other host species
Summary
The harlequin ladybird Harmonia axyridis (Pallas) is a species of Asiatic origin that became invasive in the late 1980s in North America and subsequently in other continents. Based on the available data, we only analyzed rates of parasitism (and emergence in the case of D. coccinellae) between the native area of H. axyridis and its invaded regions, between different ladybird species, and over. Harmonia axyridis is a host of D. coccinellae (Fig. 3), with reports both within its native range and in all invaded continents (Table 2), but parasitism and emergence rates are usually low in comparison with other host species This widely distributed minute wasp is a larval-pupal endoparasitoid of many ladybird species, mostly in the tribes Coccinellini and Chilocorini (Ceryngier et al 2012) It parasitizes H. axyridis in its native range in Western Siberia (Filatova 1974) and the Russian Far East (Kuznetsov 1987, 1997) as well as in the invasive. True parasites, such as the mite Coccipolipus hippodamiae (McDaniel and Morrill), the nematode Parasitylenchus bifurcatus, and the fungus Hesperomyces virescens Thaxter, are believed to have been acquired by the populations of the harlequin ladybird in the invaded range (Ceryngier and Twardowska 2013; Haelewaters et al 2016, 2017)
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