Complex host marking in the cabbage root fly

The cabbage root fly marks an oviposition site with two different chemical messages, Plants that were exposed to ovipositing flies are less acceptable than control plants, while sand particles that were closely associated wit h an actual oviposition site stimulate oviposition. By combining the inform ation from these opposing messages, the cabbage root fly may be able to opt imise the size of its egg clusters in relation to the food available for th e larvae. The findings might account for the aggregated oviposition observe d ill this species.