Table 1.

Predictions following the arrival of Harmonia axyridis in Britain (Majerus et al., ²⁰⁰⁶) alongside a summary of recent evidence, supporting references, and overall conclusions, based on current understanding, with respect to the importance of factors in determining success of invasion by this species

Prediction	Evidence	References	Conclusion
Eurytopic nature of H. axyridis will contribute to rapid spread	The range of host plant associations and widespread distribution of H. axyridis in Britain reflect the eurytopic nature of this species, although coniferous woodlands may negatively affect the spread of H. axyridis.	Brown et al. (2008b, 2011a)	+
	Habitat breadth is an important factor contributing to the invasion success of H. axyridis.
Climatic adaptability of H. axyridis will give it a competitive advantage over some of the more niche-specific native ladybirds	Climatic conditions have not been a barrier to the colonisation and spread of H. axyridis in southern Britain, but are speculated to have limited its abundance in northern England and in Scotland.	Comont et al. (2012) and Purse et al. (2014)	+/?
	There are clear discrepancies between the observed and predicted (climate model) distributions of H. axyridis, and it is apparent that climate is an important factor in determining the spread of this species but alongside other interacting biotic and abiotic factors.
Maritime climate of Britain will allow H. axyridis to breed throughout the summer, with no requirement for a summer dormancy	Continual breeding of this species is apparent and at least two generations of H. axyridis have been observed each year since arrival.	Brown et al. (2008b) and Roy et al. (2011a)	+
	Multivoltinism contributes to the rapid rate of population growth of H. axyridis each year and, consequently, to spread.
Phenotypic plasticity will allow H. axyridis to successfully and regularly extend its breeding season to September, October, and even into November	Phenotypic plasticity displayed by H. axyridis enables local adaptation at temporal and spatial scales; increase in autumnal melanisation may have accelerated the spread of H. axyridis.	Michie et al. (2010) and Purse et al. (2014)	?
	Further work is required to elucidate the importance of phenotypic plasticity in the invasion success of H. axyridis.
H. axyridis will spread across the entire British mainland by 2008	The first record of H. axyridis in Scotland was in 2007. However, there are relatively few records in Scotland and its distribution and breeding there are limited.	Brown et al. (2008a,2008b, 2011b) and Roy et al. (2011a)	+
	High dispersal ability of this species has clearly been demonstrated in most of England and Wales.
Spread and increase of H. axyridis in Britain may therefore prove to be beneficial to crop systems by restricting aphid numbers below economically damaging levels and so reduce the use of chemical pesticides	Recent research highlights the importance of H. axyridis as an aphid predator in crop systems in the UK.	Wells (2011)	?
	Further work is required to explore the ecosystem-level impact of H. axyridis on pest insects and particularly the ecosystem service provided by this alien predator.
Harmonia axyridis is likely to have a negative effect on other aphidophages in three ways: resource competition, intra-guild predation, and intraspecific competition	There is considerable evidence of intra-guild predation from laboratory and field observations.	Ware and Majerus (2008), Ware et al. (2009), Wells et al. (2010), Brown et al. (2011a), Wells (2011), Roy et al. (2012) and Brown et al. (2014)	+
	Observations from the UK Ladybird Survey highlight a strong correlation between the presence of H. axyridis and declines in the distribution of native ladybird species.
	Further work is required on competitive interactions, although recent research in laboratory mesocosms suggests that high aphid density does not reduce intra-guild predation.
	There is considerable evidence of negative effects of H. axyridis on other species, but effects on ecosystem function require further work.
Efficient chemical defence and relatively large size would provide H. axyridis with a significant reproductive advantage over many native British species	A few studies indicate the importance of chemical defence and body size in intra-guild interactions.	Bezzerides et al. and (2007) and Ware et al. (2008)	+/?
	The importance of chemical defence and large size in contributing to reproductive advantage of H. axyridis over native species requires further investigation.
H. axyridis will become a nuisance to humans	There have been many reports of H. axyridis forming large aggregations in domestic dwellings, and in some cases people have reported this species as a nuisance.	Roy et al. (2011a)	−
	There is some evidence of negative effects on humans.

+, important factor; –, unimportant; ?, undecided.