The role of predators and parasitoids in the regulation of insect populations is widely reported in the context of both pest and non-pest insects. However, this is not the case for pathogens (entomopathogens). Indeed, most studies on insect life history refer only to predators and parasitoids when considering natural enemy guilds, even though naturally occurring entomopathogens are undoubtedly more diverse and widespread. This is certainly the case with the Coccinellidae; the natural enemies of coccinellids have been the subject of a number of review articles but pathogens receive only brief mention. In this review we attempt to address the balance and consider the interactions of natural populations of Coccinellidae with entomopathogenic fungi. Most research on entomopathogens and Coccinellidae focuses on the non-target impact of biorational insecticides against coccinellids and the impact of fungal infections upon aggregations of overwintering coccinellids; with the former overwhelmingly dominating the literature. Given the prominence of coccinellids in classical and conservation biological control, it is surprising that studies have not measured the natural impact of pathogenic fungi upon introduced species or natural populations of Coccinellidae, as has been done with numerous insect pest species. Here we review the literature on the intriguing interactions between coccinellids and fungal pathogens. We examine the literature on direct infection (sub-lethal and lethal) of coccinellids by pathogenic (Beauveria bassiana, Metarhizium anisopliae, Paecilomyces fumosoroseus) or parasitic (Hesperomyces virescens). We also consider the role of intra-guild predation (on the aphid-specific fungus Pandora neoaphidis and Beauveria bassiana) and finally indirect interactions such as coccinellids dispersing P. neoaphidis. We suggest that fungal pathogens are all too often forgotten natural enemies and future research should address the profound absence of knowledge in this field.
Development and survival of larvae of two predatory ladybird species, Harmonia axyridis (Pallas) and Coccinella septempunctata L. on hibiscus (Hibiscus syridis L.) trees was followed daily outdoors during four seasons. Data were analysed and stage-specific mortality in a stage-structured model was estimated using Manly's (1997) method. Subsequently, key factor analysis was used to determine the life stages in which the daily mortality was best correlated with the total mortality during larval life. Consistently with the results from the first two years, the larvae suffered the greatest mortality during the first and fourth instars. The k-values for these two instars were also best correlated with those for the whole larval life, especially in H. axyridis.
We surveyed ladybirds (Coleoptera: Coccinellidae) in 10 stands of Scots pine (Pinus sylvestris), all monoculture stands 5–100 years old, in western Slovakia, Central Europe, over two successive periods, October 2013 – March 2014 and October 2014 – March 2015. The winter in each period was exceptionally mild. Ladybirds were collected from the lower branches of pine trees using beating trays and were present in 61% of the 1040 samples (one sample containing ladybirds from 20 branches, 1 m long each). In total 3965 individuals of 20 species were recorded. Non-conifer dwelling species associated with broadleaved trees or herbaceous plants prevailed (45% of species), followed by conifer specialists (40%) and generalists (15%). Although 13 species were found at least in one winter month, December, January or February, only four of them, Exochomus quadripustulatus, Coccinella septempunctata, Harmonia axyridis and Hippodamia variegata, were recorded continually during both winters. The number of species, the abundance of all ladybirds and the abundance of dominant species (E. quadripustulatus, C. septempunctata and H. axyridis) decreased from late autumn towards winter and remained lowest during this most adverse time of the year for ladybirds. Overwintering species assemblages of ladybirds changed over time and varied with age of pine stand. Our results suggest that Scots pine in Central Europe supports species rich assemblages of ladybirds from late autumn to early spring and, being widely distributed, it could be suited to winter surveying of ladybirds at large spatial scales to reveal behavioural and ecological responses of species to changing weather or different climates.
Factors were examined that could be responsible for the predominance of Coccinella septempunctata (C7) in most habitats of the Palaearctic and for its successful invasion of the Nearctic Region. C7 is euryphagous, but less polyphagous than Harmonia axyridis or Coleomegilla maculata in that it cannot develop or reproduce on non-aphid food. The intraguild status of C7 is intermediate. Although adult size is large, preimaginal stages are palatable to those of H. axyridis and Adalia bipunctata, whereas it is not an intraguild predator of these species. Although these traits appear to be neutral or negative, many aspects of population plasticity are advantageous for C7, often acting in concert with a bet-hedging strategy. Given its high mobility and eurytopy, the inhibition of oviposition in the presence of conspecific larval trails represents an adaptive advantage that favors increased egg dispersal and lowers the risk of offspring mortality due to cannibalism. The ability to temporarily suspend oviposition, combined with heterogenous voltinism and diapause tendencies, enable a portion of C7 populations to feed and reproduce on unpredictably occurring aphid populations. An absence of reproductive diapause in males and pre-hibernation mating are other significant adaptations, along with the tendency to produce offspring in excess of the carrying capacity of local food resources. We suggest that one explanation for the broad geographic success of C7 resides in an ecological plasticity that is based on both genetic and phenotypic polymorphisms.