In the Republic of Benin, the African pink stem borer Sesamia calamistis Hampson is kept under control by the two scelionid egg parasitoids Telenomus busseolae (Gahan) and T. isis (Polaszek). A third species, the trichogrammatid Lathromeris ovicida Risbec, although commonly obtained from egg batches, is of low importance. High egg and egg batch parasitism by Telenomus spp. at low host densities suggests excellent host-finding capacity. Previously it was hypothesized that pheromones produced by calling S. calamistis virgins play an important role in attracting the parasitoids to the area where oviposition is likely to occur. Thus, after determining the effect of age (1-4 days) on the calling rhythm of S. calamistis, 1-day-old virgin females were chosen to investigate the response of the parasitoids to calling and noncalling females and two empty controls, in a four-arm olfactometer. The results showed that calling started earliest and lasted longest with 1-day-old females, but was similar for 2- to 4-days-old females. The percentage of females calling was higher in early than latter scotophases. The highest percentage of active females was obtained between 8 and 9 hr after the beginning of the first scotophase. All three parasitoid species responded to calling females, while there were no differences between noncalling females and the empty controls. The response pattern was similar for the two Telenomus spp. but considerably weaker for L. ovicida, reflecting differing host specificity of the three parasitoid species.