Atypical phenology of aphids (Aphidoidea) and their ladybird predators arising from fluctuating spring temperatures

April and May 2019 were characterised by strongly fluctuating temperatures in the Dutch provinces of Noord-Brabant and Limburg, which led to changes in aphid populations and the phenology of the ladybirds feeding on them. Aphid species reached high abundances on some herbs and shrubs, but species on some trees were virtually absent. The immediate and reproductive effects on ladybird species were variable. Population sizes at the end of the year suggested that the total reproductive output of generalist ladybirds had been minimally affected, probably due to their broad dietary ranges. However, the fully arboreal Adalia decempunctata was much less abundant, likely due to scarcity of its tree-dwelling prey. In 2021, similar spring conditions again resulted in few aphids and ladybirds on trees, suggesting that some of the changes observed in 2019 might become more permanent.