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We compared the toxicity of the neonicotinoids imidacloprid, thiacloprid, thiamethoxam, acetamiprid, and clothianidin in terms of the survival and reproduction of 2 species of soil invertebrates, Folsomia candida and Eisenia andrei. Tests were performed using LUFA 2.2 natural soil, following standard protocols aimed at answering 2 questions: 1) Is there a difference in the toxicity between pure compound and its formulation? and 2) Is there a difference in the sensitivity of the species exposed to the same compound? For E. andrei, formulations and pure compounds had similar toxicity to both endpoints tested. For F. candida, acetamiprid and imidacloprid had different toxicities, with acetamiprid being 4 times more toxic to survival (median lethal concentration [LC50] 0.12 mg active substance [a.s.]/kg dry soil) and imidacloprid being 4 times more toxic to reproduction of the springtail (median effect concentration [EC50] 0.25 mg a.s./kg dry soil) than their commercial formulations. The most toxic compound to E. andrei was acetamiprid (LC50 0.80 and EC50 0.35–0.40 mg a.s./kg), and the most toxic to F. candida was clothianidin (LC50 0.07 and EC50 0.05 mg a.s./kg). Estimated risk ratios indicated that only one application/yr of clothianidin in the formulation Poncho® may pose a threat to the populations of springtails and earthworms. Environ Toxicol Chem 2020;39:548–555. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Collembolans comprise one of the most abundant groups of soil invertebrates within the arthropods. The parthenogenetic species Folsomia candida (Willem, 1902) is the most well-studied representative, being used since the beginning of the 1960s as a model organism for assessing toxicity of chemicals in soil. In this paper we aimed at answering three questions by exposing four different species of springtails (F. candida, Folsomia fimetaria, Sinella curviseta and Heteromurus nitidus) to the neonicotinoids imidacloprid and thiacloprid: i) How representative as a model organism is F. candida for species of springtails that reproduce sexually? (ii) How suitable are other species of springtails to be used as model organisms for ecotoxicological testing? (iii) Is it possible to use the life history of these species to extrapolate the impact of neonicotinoids on the population level? Our results showed that F. candida is a good model organism, despite being the most sensitive species tested, when analysing both endpoints – survival and reproduction. The tests performed with S. curviseta and H. nitidus showed that they could be used as surrogates in ecotoxicity tests, and also to predict how their population might be affected after being exposed to chemicals. The adjustments made to the test performed with F. candida: introducing adults (20–22 days old) into the test jars and exposing them for 21 days instead of 28 days, proved to be as efficient as the standardized test guideline (OECD 232, 2009).