Aphis spiraecola (Patch) virginiparae were reared for 3 generations on the dropwort, Oenathe javanica DC, under low temperature ($15^{circ}$) and short days (10L:14D) for artificial induction of sexual forms (Hong and Boo, 1998). These oviparae, artificially induced in the third generation in the laboratory, showed a typical behavior of releasing sex pheromone by waving their hind tibiae and abdomen in the air during photophase. The air around these oviparae, individually or in groups, was collected and analyzed by gas chromatography for pheromone components. (+)-(4aS,7S,7aR)-nepetalactone and (-)-(1R,4aS,7S,7aR)- nepetalactol were detected in the ratio of 6:1∼8:1. For wild oviparae collected from an apple orchard and a spiraea arboretum during Oct. 1995.∼ Nov. 1996, the ratio between the two components was around 2:1. Oviparae showed a circadian rhythm in release of sex pheromone, with beginning to release nepetalactone at the start of lights-on and stopping with lights-off. This rhythm was also maintained in an all dark condition. The sex pheromone was always detected during the photophase, even when the photoperiod was altered to a longer regime, for example from 10L:14D to 16L:8D.