Invertebrate attack rates in crop fields are driven by prey toughness rather than size

• Six prey types of varying toughness and size were monitored in crop fields. • Prey toughness rather than size influenced predation rates. • Prey types acted as ‘filters’ on the predator community. • Incomplete predator–prey trait matching for carabids and insect prey. • Promoting carabids likely benefits the control of a wide range of insect pests. Insect pests vary in size and toughness across species and life stages, and are attacked to varying degrees by different predators. Feeding experiments suggest that both prey and predator (e.g. carabid) traits shape these predator–prey interactions. Here, we investigate how prey size and toughness affect invertebrate predation in the field, which predator taxa are involved, and how carabid traits influence predator–prey interactions. This will improve our understanding of how predator communities control the pest complexes associated with a given crop or crop rotation. We found that attack rates on dead sentinels were lower for hard than soft prey, with prey size being less important. Carabids were among the major predators of all prey types, while aphids attracted the most diverse predator assemblage. Carabid body size and bite force had little influence on their attack rates, but species with higher activity density contributed more frequently to prey damage. Our results suggest that ground-active predator communities, as currently observed in conventional cereal fields, are likely to exert variable control over insect pests of different prey toughness. Consequently, the prey type selected for rapid ecosystem function assessment acts as a ‘filter’ on the predator community, influencing the measured attack rate. Nonetheless, promoting predator abundance, particularly carabids, could improve regulation of fairly soft-bodied insect pests, whereas controlling hard-bodied pest species or life stages may require additional or different predator species.