Reflections on the long-term assessment of ladybird (Coleoptera: Coccinellidae) populations in the Czech Republic and the United Kingdom

Large fluctuations in predatory ladybird populations between years makes it difficult to assess the conservation status of this important group of beetles. Monitoring of their long-term trends may be achieved using systematic structured surveys or by the collation of incidental records. Since the 1970s Alois Honěk and colleagues in the Czech Republic have used the former approach to generate some of the best long-term ladybird datasets globally. Declines in species, particularly Coccinella septempunctata Linnaeus, 1758, have been observed in these datasets, and explanations for the declines offered. Here we reflect on the work of Alois Honěk and colleagues and contrast their approach to monitoring ladybirds with that taken in the UK. UK ladybird trends have been derived from careful analyses of incidental records collected by citizen scientists, along with some systematic structured surveying. We compare the trends suggested by Czech and UK data. There are broad similarities in trends for several species, namely Adalia bipunctata (Linnaeus, 1758), Coccinella undecimpunctata Linnaeus, 1758 and Propylea quattuordecimpunctata (Linnaeus, 1758) (decreasing trends) and Harmonia axyridis (Pallas, 1773) and Hippodamia (Adonia) variegata (Goeze, 1777) (increasing trends). Conversely the trends for Adalia decempunctata (Linnaeus, 1758), Coccinella quinquepunctata Linnaeus, 1758, C. septempunctata and Calvia quattuordecimguttata (Linnaeus, 1758) are dissimilar in the two countries. We briefly explore whether similar drivers of change were at play in the Czech Republic and UK. In both countries, changes in agricultural practices (notably less small grain cereal-growing and reduced fertilizer use that lowers aphid numbers) may account for some of the ladybird population trends observed.