Newly emerged males ofHyphantria cunea (Drury) (Lepidoptera: Arctiidae), marked with different fluorescent colors, were recaptured by pheromone trapping. Three Uni-traps, baited with (3Z,6Z)9,10-epoxyheneicosadiene, (9Z,12Z,15Z)octadecatrienal, and (3Z,6Z)9,10-epoxyheneicosa-triene in a 1:10:1 ratio, total 6 mg/dispenser, were placed in a line 15 m apart, perpendicular to the dominant wind ... [Show full abstract] direction, and checked after 12, 36, and 60 hr. At dusk, releases of 10–25 males were made over distances from 30 to 250 m, during 4 periods over a soybean field (nonhost plant). Recapture rates were high; of a total of 176 males released, 115 were recaptured with 88% of these within 12 hours. Between 40 and 100% of males were recovered over shorter distances (30–150 m), and between 10–24% at longer distances (200 and 250 m). No other species or unmarked males were captured. The trapping period showed little effect on recaptures. The central trap of the three traps had somewhat higher catches, but the slope of the regression of recapture over distance did not differ among traps. There was a significant decline of recapture over distance (r=−0.56) for catches of individual traps but a large scatter. Summed recaptures per distance gave less scatter and hadr=−0.86, allowing calculation of the maximum sampling range (R
) after 60 hr as 340 m with a 95% confidence interval of 190–710 m (regression of arcsin √p and √R). The area of sampling, found by integrating the probability function of recapture over distance, from the source to maximumR, was 7 ha. The high recapture rates and the longR,. compared to those in the literature for other taxa, indicate that pheromone traps are highly efficient sampling devices in this species.