Parasitoid behaviour and Bt plants

Transgenic crops that express genes targeted against insect pests may also affect non-target insects. For example, lacewings1 and monarch butterflies2 have been reported to be susceptible to toxins from Bacillus thuringiensis (Bt) that are expressed in Bt transgenic plants, although these results were obtained in small-scale laboratory assays in which insects were exposed to high levels of transgenically expressed toxin in no-choice tests. We show here that the behaviour of non-target insects can also play a part in determining how their populations will be affected by Bt plants.