Ultrastructural observations on antennal sensilla of Cnaphalocrocis medinalis (Lepidoptera: Pyralidae)

The morphology and ultrastructure of the antennal sensilla of Cnaphalocrocis medinalis (Lepidoptera: Pyralidae) was studied by scanning and transmission electron microscopic techniques. Eight morphological types of sensillum were recorded in both sexes: sensilla trichodea (S. trichodea), sensilla basiconc (S. basiconc), sensilla coeloconica (S. coeloconica), sensilla styloconica (S. styloconica), sensilla squamous (S. squamous), sensilla auricillica (S. auricillica), Böhm bristles (B. bristles), and sensilla cavity (S. cavity). S. trichodea were the most abundant sensilla and were distributed over the entire antennal surface. Four different types of S. trichodea and S. basiconc were observed. The number of S. basiconc and S. coeloconica of males were greater than those of females of C. medinalis. S. squamous formed on the dorsal part of the antenna, as a cluster in females and as in a line in males. Higher magnification revealed that S. basiconc had an olfactory function, while the character of longer length of these sensilla suggested that they also played a rolein sensing mechanical or other chemical stimuli. Transmission electron microscopy (TEM) of S. squamous revealed nonporous walls suggesting a non-olfactory function. S. coeloconica, S. styloconica, and S. cavity may be involved in the perception of humidity, temperature, heat, and CO₂. Because of their particular location, we infer that B. bristles may function in sensing the position and movements of the antennae, while the function of S. auricillica is as yet unknown. The results obtained provide direct morphological evidence that antennae possess structures that can play a role in finding mates and locating host plants.