Individual trail marking by larvae of the scarce swallowtail Iphiclides podalirius L. (Lepidoptera; Papilionidae).

Starting from permanent resting sites covered with silk, the solitary and territorial larvae of I. podalirius spin silk trails leading to feeding sites. It is shown that the silk contains a volatile trail marker. The larvae recognize their own trails and prefer them to those laid by conspecific caterpillars. Trail marking appears to be widespread among larvae of Lepidoptera.