Aphidophagous and coccidophagous coccinellids come into conflict with homopteran‐tending ants for access to food. Antagonistic interactions between coccinellids and ants may be competitive or non‐competitive. Competitive interactions occur when coccinellids attack aphids or coccids that are being tended by ants for honeydew. Non‐competitive interactions include all interactions away from ant‐tended homopteran colonies. We here review observations and studies of such interactions. We note that most competitive interactions occur at times when untended aphids/coccids are scarce. We describe the chemical and physical defences that coccinellids use against ant aggression and consider whether these have evolved as general anti‐predator deterrents or specifically in response to ants. Myrmecophilous coccinellids are then considered, with particular focus on the two most studied species, Coccinella magnifica and Platynaspis luteorubra. We note that the myrmecophily of the two species has the same adaptive rationale—to enable the ladybirds to prey on ant‐tended aphids at times of aphid scarcity—but that it is based on different traits to facilitate life with ants. Finally, we consider the role of ants in the evolution of habitat specialisation in some coccinellids.

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A growing body of evidence suggests trophic generalism (feeding on resources from more than one trophic level and/or on different resources of the same trophic level) is a widespread feature among ground beetles (Coleoptera: Carabidae). However, it remains unclear whether trophic generalism applies to single individuals, at the intrapopulation or interpopulation level. Here we present stable isotope data (δ15N, δ13C) of seven common European carabid species on an archipelago of 18 lake islands in northeastern Poland. We found strong differences in isotopic ratios between individuals of the same population as well as between different populations, indicating that carabids are opportunistic feeders and that the degree of opportunism differs between habitats and between islands. Trophic niche breadth as assessed by isotopic ratios was influenced by local habitat diversity. We suggest that opportunistic usage of different local resources results in striking differences between local populations and a very broad trophic niche observed at regional level.

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