A widely-used technique for sampling arthopods in forage crops employs the D-Vac7® suction sampler (Dietrick 1961). Various attachments, such as a series of different-sized collecting heads, make the D-Vac a versatile sampling tool. For extensive sampling to estimate population parameters of several species of insects and spiders in alfalfa, we have found the ft2area collecting head to be the most useful attachment. Although this has proven generally satisfactory, a source of error was noted with certain species. We observed that some of the large insects and spiders are capable of escaping from the D-Vac by climbing down the sides of the collecting bag after having been sucked into it. To prevent this, we designed a simple “escape barrier” which consists of a flange placed inside the ft2collecting head, as shown in FlG. 1. The flange encircles the entire inside circumfer was taken at each site. This was repeated in different fields on 2 dates ca. 1 month apart. On the 2 dates, 8 and 10 subsamples, respectively, were taken by each technique. The results of sampling 2 representative arthropod species, the hemipteranNabisspp. and the lycosid spiderPardosa ramulosa(McCook), are presented in Table 1.