Ants are no bees – Gaps in the assessment of relevant exposure routes to pesticides and plant incorporated protectants

Ants (Formicidae) are ubiquitous in terrestrial ecosystems, including agricultural areas and forests. They are important for soil movement, decomposition, nutrient cycling, pollination, predation, scavenging and seed dispersal. Furthermore, they serve as a crucial food source for various wildlife. However, ants are no part of current ecotoxicity testing. Here, we systematically analyze whether and how ants can be exposed to active substances from plant protection products (PPPs) or genetically modified plants (GMPs). Like other arthropods, ants can be exposed via direct contact with PPPs after application, inhalation, uptake of contaminated drinking water or diet. For plant incorporated protectants (PIPs) expressed by GMPs, dietary exposure is the only relevant exposure route. Ants exhibit a diverse dietary spectrum, including plant material, honey dew collection, fungal cultivation, scavenging, and predation. Notably, foraging for dead or weakened arthropods, e.g., treated pest organisms, represents a significant exposure route because such food may be readily available in large amounts after spraying a field. Arthropods, alive or deceased, serve as the dominant protein source for numerous ant species, essential for larval development and the egg production of the queen(s). Consequently, exposure routes, via contaminated food items, can jeopardize entire ant colonies if it reaches the queen. However, effects arising from contaminated prey are not routinely assessed, neither for non-social nor for social insects such as the honey bee, which collects only nectar and pollen and is intensively tested in the assessment of PPPs. We conclude that ecotoxicity testing in ants would fill a gap and support the assessment of biodiversity effects. To achieve this, we recommend further research to explore the exposure of the different castes and developmental stages of ants in greater detail and to develop protocols allowing for ecological risk assessments of PPPs and PIPs via dietary uptake. This comprehensive approach will contribute significantly to our understanding of the potential consequences of PPP and GMP exposure to non-target ants.