DIEL RHYTHMS OF CALLING BEHAVIOR AND SEX PHEROMONE PRODUCTION OF BEET ARMYWORM,SPODOPTERA EXIGUA (LEPIDOPTERA:NOCTUIDAE)*

Abstract Beet armyworm (BAW), Spodoptera exigua, is becoming one of more and more serious pests in China in recent years. As a part of research program of sex pheromone and its application of BAW in China, the hourly and daily variation of calling behavior and pheromone production of BAW females were investigated. Both calling behavior and titers of 4 sex pheromone components showed distinct diel rhythms, and the two peak periods were synchronous. In comparison, the calling activity lasted shorter period of time with a longer peak time, whereas the production of the sex pheromone lasted throughout the whole scotophase and part of the photophase with a very short peak time. The calling behavior began at the middle scotophase, reached the maximum at the middle‐later scotophase, and continued the maximal calling activity until the end of the scotophase. When the light was on, the calling percentage reduced sharply, and all females stopped calling 1 hour later. The variation patterns of the 4 pheromone components in the glands of the 3 day old moths were similar from one to another. From 0.5 h before to 4.5 h into scotophase, the titers increased slightly, but at 6.5 h they showed a significant increase up to the peak values of the scotophase. Soon at 8.5 h into the scotophase, they decreased significantly and thereafter gradually to undetectable level at 4.5 h into the next photophase. The daily change experiment showed that BAW females began calling at 0 scotophase, became fully active in calling at 3rd scotophase, and maintained the calling activity to 7th scotophase. There was no significant difference in pheromone titers among different day‐old moths.