Ultrastructure of the sensory complex on the maxillary and labial palpi of the colorado potato beetle, Leptinoarsa decemlineata

Sensilla on the maxillary and labial palpi of Leptinotarsa decemlineata were examined by scanning and transmission electron microscopy. There are a total of 370 sensilla on the apical tip of the maxillary palpi and 130 on the labial palpi. Four morphologically different types of sensilla are present on the maxillary palpi, three of which are common to the labial palpi. Type A sensilla, unique to the maxillary palpi, and type C sensilla have the structural characteristics of olfactory sensilla. Types B and D, with an apical pore, are considered contact chemoreceptors. Cuticular specializations, interrelationships of enveloping cells, comparative morphometry of dendrites, distribution of each sensillar type, and the predominance of olfactory sensilla are discussed in relation to feeding behavior.