PHEROMONE SENSILLA OF THE BEET ARMYWORM, SPODOPTERA-EXIGUA (HUBNER) (LEPIDOPTERA, NOCTUIDAE)

Scanning electron microscopy of the antennae of the beet armyworm, Spodoptera exigua, demonstrated the presence of sensilla auricillica, chaetica, coeloconica, styloconica, and two kinds of trichodea (ridge-type trichodea and ridgeless-type trichodea), and suggested that auricillica, coeloconica and trichodea were olfactory sensilla. Ridge-type trichodea were further discriminated into two subtypes by their length. Long ridge-type trichodea (type 1) were male specific and distributed only in the proximal half (subsegment 1-34) of the antenna. About 70% of short ridge-type trichodea (Type 2) were present in the distal half (35-distal end) of the male antenna. In females, type 2 and ridgeless-type trichodea (type 3) were found on the entire antenna and were not distributed partially. Type 2 trichodea of male moth were also sensitive to sex pheromone as well as type 1 trichodea, although the ridgeless-type trichodea (type 3), auricillica and coeloconica did not respond to the pheromones.