Sensory structures involved in prey detection on the labial palp of the ant-hunting beetle Siagona europaea Dejean 1826 (Coleoptera, Carabidae)

The ultrastructure and distribution of sensilla on the labial palps of a myrmecophagous carabid beetle, Siagona europaea, were investigated using scanning and transmission electron microscopy techniques. Five types of sensilla were identified: three types of sensilla basiconica on the apical sensory area and two types, one sensillum trichodeum and one coeloconicum, on the external palp surface. On morphological grounds, the s. basiconica type 1 were considered as olfactory, the type 2 as gustatory, the type 3 and the s. trichodeum as mechanoreceptive, and the s. coeloconicum as a thermo\u2044 hygroreceptor. Their function is discussed in relation to prey detection and habitat adaptation