The Oriental fruit fly Bactrocera dorsalis learns to avoid an odorant associated with a toxin in food

To adapt to the environment, it is important for insects to learn and evaluate food quality to avoid toxins in food. Currently, attractants are widely used for pest control, as they are environmentally friendly pesticides. Learning to associate an attractive odor with a toxin in food may influence insect behaviour in response to the attractant, thus affecting its application. In this study, we found that Bactrocera dorsalis, a serious pest of fruits and vegetables, can learn to associate a male lure compound, methyl eugenol (ME), with a sucrose solution contaminated with N,N-diethyl-3-methyl benzoyl amide (DEET), a common insect repellent and decrease its proboscis extension response (PER) elicited by ME. Learning with DEET depends on its concentration, and flies exhibited significant aversive memory formation when high concentrations were used. Aversive-DEET memory formed with 0.6% DEET persisted for at least 24hr. We also found that aversive memory formed during training could be transferred to a behavioural response in an operant context.