When adult femaleHeliothis virescens(F.) were collected while calling and rinsed with ether, the washes contained a volatile material attractive to males, but ether washes of whole moths and abdominal tips soaked for about 2 h were not attractive. The attractive material was not obtained from females that were not calling. A light of low intensity placed beneath cages of females stimulated calling among those that had previously been inactive. In the field, native males began responding to concentrated washes of pheromone about 3 h after sunset, but 90% of the total number of males captured in pheromone- or female-baited traps were taken between 2300 and 0400 h.