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.