Factors determining the effects of pesticides upon butterflies inhabiting arable farmland

The importance of farmland habitats for butterfly populations and their accidental or intentional contamination from pesticide applications is discussed. The current literature concerning the effects of insecticides and herbicides upon lepidopteran species, such as direct mortality and sublethal changes in fecundity and longevity, and removal of adult nectar and larval host plants is detailed. In order to aid predictions of butterfly vulnerability in field boundaries, factors determining a species' exposure and susceptibility to particular compounds are examined. These range from chemical properties of the compound, intrinsic susceptibility of the species, exposure of the butterfly-related plants to drifting pesticides and species-dependent ecological factors determining their within-boundary behaviour and dispersal. Finally, farmland manage ment practices, such as the employment of 'Conservation Headlands' and increased hedge boundary width and floral diversity, are discussed in relation to their intended improvement of, and reduced pesticide contamination of, butterfly habitats.